Magnetic reversals

Summary In order to determine the origin and nature of the Earth's magnetic field and to test the various hypotheses which have been advanced to explain the field, it is desirable to determine the history of this field throughout geologic time and to investigate more carefully its spatial variations, both inside and outside the Earth's surface. This research is concerned with the determination of the history of the Earth's field as it can be deduced from the present polarization of crustal material. Unconsolidated fresh‐ and salt‐water sediments have been investigated. These sediments are in the form of clays and offer one of the simplest types of polarization, since the clays can be redeposited under laboratory conditions. A particularly lengthy investigation of the polarization of glacial varves has been made, together with measurements on core samples of sediments from the Pacific. From a study of anomalous deposits in the glacial clays, the geologic stability of the polarization of these clays has been established over geologic time. From the measurements of the glacial clays, it is concluded that the Earth's field has not changed substantially in direction or intensity during the last 15,000 years. From measurements of the Pacific cores, it is tentatively concluded that the direction and intensity of the Earth's magnetic field has probably remained substantially constant during the last million years. A much more complete investigation is necessary to verify these tentative conclusions. It would be desirable to extend the measurements to periods of the order of one billion years. These results are consistent with the “fundamental” theory proposed by Schuster, Babcock, and Blackett, but do not provide positive evidence to support this theory.

@article{doi101029te053i004p00349,
    author = "Johnson, E. A. and Murphy, Thomas and Torreson, O. W.",
    title = "Pre‐history of the Earth's magnetic field",
    year = "1948",
    journal = "Terrestrial Magnetism and Atmospheric Electricity",
    abstract = "Summary In order to determine the origin and nature of the Earth's magnetic field and to test the various hypotheses which have been advanced to explain the field, it is desirable to determine the history of this field throughout geologic time and to investigate more carefully its spatial variations, both inside and outside the Earth's surface. This research is concerned with the determination of the history of the Earth's field as it can be deduced from the present polarization of crustal material. Unconsolidated fresh‐ and salt‐water sediments have been investigated. These sediments are in the form of clays and offer one of the simplest types of polarization, since the clays can be redeposited under laboratory conditions. A particularly lengthy investigation of the polarization of glacial varves has been made, together with measurements on core samples of sediments from the Pacific. From a study of anomalous deposits in the glacial clays, the geologic stability of the polarization of these clays has been established over geologic time. From the measurements of the glacial clays, it is concluded that the Earth's field has not changed substantially in direction or intensity during the last 15,000 years. From measurements of the Pacific cores, it is tentatively concluded that the direction and intensity of the Earth's magnetic field has probably remained substantially constant during the last million years. A much more complete investigation is necessary to verify these tentative conclusions. It would be desirable to extend the measurements to periods of the order of one billion years. These results are consistent with the “fundamental” theory proposed by Schuster, Babcock, and Blackett, but do not provide positive evidence to support this theory.",
    url = "https://doi.org/10.1029/te053i004p00349",
    doi = "10.1029/te053i004p00349",
    openalex = "W2062761864"
}

Abstract The westward drift of the non-dipole part of the earth’s magnetic field and of its secular variation is investigated for the period 1907-45 and the uncertainty of the results discussed. It is found that a real drift exists having an angular velocity which is independent of latitude. For the non-dipole field the rate of drift is 0.18 ± 0-015°/year, that for the secular variation is 0.32 ±0-067°/year. The results are confirmed by a study of harmonic analyses made between 1829 and 1945. The drift is explained as a consequence of the dynamo theory of the origin of the earth’s field. This theory required the outer part of the core to rotate less rapidly than the inner part. As a result of electromagnetic forces the solid mantle of the earth is coupled to the core as a whole, and the outer part of the core therefore travels westward relative to the mantle, carrying the minor features of the field with it.

@article{doi101098rsta19500014,
    author = "Bullard, E. C. and Freedman, Cynthia and Gellman, H. and Nixon, Jo",
    title = "The westward drift of the Earth's magnetic field",
    year = "1950",
    journal = "Philosophical Transactions of the Royal Society of London Series A Mathematical and Physical Sciences",
    abstract = "Abstract The westward drift of the non-dipole part of the earth’s magnetic field and of its secular variation is investigated for the period 1907-45 and the uncertainty of the results discussed. It is found that a real drift exists having an angular velocity which is independent of latitude. For the non-dipole field the rate of drift is 0.18 ± 0-015°/year, that for the secular variation is 0.32 ±0-067°/year. The results are confirmed by a study of harmonic analyses made between 1829 and 1945. The drift is explained as a consequence of the dynamo theory of the origin of the earth’s field. This theory required the outer part of the core to rotate less rapidly than the inner part. As a result of electromagnetic forces the solid mantle of the earth is coupled to the core as a whole, and the outer part of the core therefore travels westward relative to the mantle, carrying the minor features of the field with it.",
    url = "https://doi.org/10.1098/rsta.1950.0014",
    doi = "10.1098/rsta.1950.0014",
    openalex = "W2138460843"
}

We consider the dynamical consequences of Biermann's suggestion that gas is often streaming outward in all directions from the sun with velocities of the order of 500-1500 km/sec. These velocities of 500 km/sec and more and the interplanetary densities of 500 ions/cm3 (1014 gm/sec mass loss from the sun) follow from the hydrodynamic equations for a 3 X 1060 K solar corona. It is suggested that the outward-streaming gas draws out the lines of force of the solar magnetic fields so that near the sun the field is very nearly in a radial direction. Plasma instabilities are expected to result in the thick shell of disordered field (10- gauss) inclosing the inner solar system, whose presence has already been inferred from cosmic-ray observations.

@article{doi101086146579,
    author = "Parker, E. N.",
    title = "Dynamics of the Interplanetary Gas and Magnetic Fields.",
    year = "1958",
    journal = "The Astrophysical Journal",
    abstract = "We consider the dynamical consequences of Biermann's suggestion that gas is often streaming outward in all directions from the sun with velocities of the order of 500-1500 km/sec. These velocities of 500 km/sec and more and the interplanetary densities of 500 ions/cm3 (1014 gm/sec mass loss from the sun) follow from the hydrodynamic equations for a 3 X 1060 K solar corona. It is suggested that the outward-streaming gas draws out the lines of force of the solar magnetic fields so that near the sun the field is very nearly in a radial direction. Plasma instabilities are expected to result in the thick shell of disordered field (10- gauss) inclosing the inner solar system, whose presence has already been inferred from cosmic-ray observations.",
    url = "https://doi.org/10.1086/146579",
    doi = "10.1086/146579",
    openalex = "W2045483269"
}

Shallow submerged lines of force of an initial axisymmetric dipolar field of 8 X 1021 maxwells are drawn out in longitude by the differential rotation (after the suggestion of Cowling) to produce a spiral wrapping of five turns in the north and south hemispheres after 3 years. The amplification factor approaches 45, with a marked dependence on latitude. Twisting of the irregular flux strands by the faster shallow layers in low latitudes forms "ropes" with local concentrations that are brought to the surface by magnetic buoyancy to produce bipolar magnetic regions (BMR's) with associated sunspots and related activity. The field intensity required for producing BMR's is reached at progressively lower latitudes according to the derived formula sin = + 1.5/(n + 3), where n is the number of years since the beginning of the sunspot cycle. This accounts satisfactorily for 's law and the Maunder "butterfly diagram." Sufficient flux rope for more than 102 BMR's is produced. "Preceding" parts of BMR's expand toward the equator as they age, to be neutralized by merging; "following" parts expand or migrate poleward so that their lines of force neutralize and then replace the initial dipolar field. This process, which involves severing and reconnection of lines of force in the corona, as well as expulsion of flux loops, need be only 1 per cent efficient. The result, after sunspot maximum, is a main dipolar field of reversed polarity. The process repeats itself, so that the initial conditions are reproduced after a complete 22-year magnetic cycle. This model accounts for Hale's laws of sunspot polarity and provides a qualitative explanation of the proponderance of "preceding" spots, of the forward tilt of the axes of older spots, of the recurrence of activity in preferred longitudes, and of Hale's chromospheric "whirls."

@article{doi101086147060,
    author = "Babcock, Horace W.",
    title = "The Topology of the Sun's Magnetic Field and the 22-YEAR Cycle.",
    year = "1961",
    journal = "The Astrophysical Journal",
    abstract = {Shallow submerged lines of force of an initial axisymmetric dipolar field of 8 X 1021 maxwells are drawn out in longitude by the differential rotation (after the suggestion of Cowling) to produce a spiral wrapping of five turns in the north and south hemispheres after 3 years. The amplification factor approaches 45, with a marked dependence on latitude. Twisting of the irregular flux strands by the faster shallow layers in low latitudes forms "ropes" with local concentrations that are brought to the surface by magnetic buoyancy to produce bipolar magnetic regions (BMR's) with associated sunspots and related activity. The field intensity required for producing BMR's is reached at progressively lower latitudes according to the derived formula sin = + 1.5/(n + 3), where n is the number of years since the beginning of the sunspot cycle. This accounts satisfactorily for 's law and the Maunder "butterfly diagram." Sufficient flux rope for more than 102 BMR's is produced. "Preceding" parts of BMR's expand toward the equator as they age, to be neutralized by merging; "following" parts expand or migrate poleward so that their lines of force neutralize and then replace the initial dipolar field. This process, which involves severing and reconnection of lines of force in the corona, as well as expulsion of flux loops, need be only 1 per cent efficient. The result, after sunspot maximum, is a main dipolar field of reversed polarity. The process repeats itself, so that the initial conditions are reproduced after a complete 22-year magnetic cycle. This model accounts for Hale's laws of sunspot polarity and provides a qualitative explanation of the proponderance of "preceding" spots, of the forward tilt of the axes of older spots, of the recurrence of activity in preferred longitudes, and of Hale's chromospheric "whirls."},
    url = "https://doi.org/10.1086/147060",
    doi = "10.1086/147060",
    openalex = "W1977971109"
}

The X rays produced by electron precipitation from the geomagnetic field have been further studied by means of scintillation counters carried on balloons launched simultaneously at four sites between Waterloo, Iowa, and Flin Flon, Manitoba, Canada. The latitude and detailed time profile were measured during two magnetic storms on September 25, 1961, and October 1, 1961. The integrated photons per centimeter2 for the two storms show very different latitude profiles. On September 25 the intensity increased to the highest latitude (64.5° geomagnetic). On October 1 the profile was highest at 55° and dropped off to a very low value at the high latitude. These differences seem connected with the fact that the September storm was of the recurrent type, and the October 1 storm was more violent and was induced by a large solar flare. The detailed comparison with the total energy stored in the magnetic field, obtained from recent measurements of the trapped radiation in the energy range comparable with the balloon measurements, shows that about one or two orders of magnitude more energy was precipitated than is normally stored quiescently, indicating that during the magnetic disturbance the addition of energy to the electrons in the magnetic field is necessary. A more extreme case, observed on July 16, 1961, at Fort Churchill and at Minneapolis, shows that during a strong magnetic sudden impulse more than two orders of magnitude more energy was precipitated than is quiescently trapped. The precipitation has been observed with the data averaged in time intervals between 120 sec and 0.1 sec. We find that during periods of intense precipitation a large fraction of the precipitation occurs in bursts of high intensity lasting only 0.1 sec. It is suggested that these rapid bursts can account for the flashes or pulsations observed in strong auroral storms. Power spectrum analysis methods have been applied to the counting rate data, and we find periodic precipitation occurring with periods of 0.8, 1.6, and 3.2 sec and higher multiples. It is suggested that this constitutes direct evidence for particle bunches near 60-kev energy oscillating between conjugate points in the geomagnetic field. A Chree analysis applied with the large impulsive bursts as zero epoch confirms this picture and shows that the same periods occur in fixed phase relationship to the bursts.

@article{doi101029jz067i010p03717,
    author = "Winckler, J. R. and Bhavsar, P. D. and Anderson, K. A.",
    title = "A study of the precipitation of energetic electrons from the geomagnetic field during magnetic storms",
    year = "1962",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "The X rays produced by electron precipitation from the geomagnetic field have been further studied by means of scintillation counters carried on balloons launched simultaneously at four sites between Waterloo, Iowa, and Flin Flon, Manitoba, Canada. The latitude and detailed time profile were measured during two magnetic storms on September 25, 1961, and October 1, 1961. The integrated photons per centimeter2 for the two storms show very different latitude profiles. On September 25 the intensity increased to the highest latitude (64.5° geomagnetic). On October 1 the profile was highest at 55° and dropped off to a very low value at the high latitude. These differences seem connected with the fact that the September storm was of the recurrent type, and the October 1 storm was more violent and was induced by a large solar flare. The detailed comparison with the total energy stored in the magnetic field, obtained from recent measurements of the trapped radiation in the energy range comparable with the balloon measurements, shows that about one or two orders of magnitude more energy was precipitated than is normally stored quiescently, indicating that during the magnetic disturbance the addition of energy to the electrons in the magnetic field is necessary. A more extreme case, observed on July 16, 1961, at Fort Churchill and at Minneapolis, shows that during a strong magnetic sudden impulse more than two orders of magnitude more energy was precipitated than is quiescently trapped. The precipitation has been observed with the data averaged in time intervals between 120 sec and 0.1 sec. We find that during periods of intense precipitation a large fraction of the precipitation occurs in bursts of high intensity lasting only 0.1 sec. It is suggested that these rapid bursts can account for the flashes or pulsations observed in strong auroral storms. Power spectrum analysis methods have been applied to the counting rate data, and we find periodic precipitation occurring with periods of 0.8, 1.6, and 3.2 sec and higher multiples. It is suggested that this constitutes direct evidence for particle bunches near 60-kev energy oscillating between conjugate points in the geomagnetic field. A Chree analysis applied with the large impulsive bursts as zero epoch confirms this picture and shows that the same periods occur in fixed phase relationship to the bursts.",
    url = "https://doi.org/10.1029/jz067i010p03717",
    doi = "10.1029/jz067i010p03717",
    openalex = "W2091715317"
}

@article{doi101126science14436261537,
    author = "Cox, Allan and Doell, Richard R. and Dalrymple, G. Brent",
    title = "Reversals of the Earth's Magnetic Field",
    year = "1964",
    journal = "Science",
    url = "https://doi.org/10.1126/science.144.3626.1537",
    doi = "10.1126/science.144.3626.1537",
    openalex = "W2021766270"
}

@article{doi1010382121193a0,
    author = "Harrison, C. G. A. and Somayajulu, B.L.K.",
    title = "Behaviour of the Earth's Magnetic Field During a Reversal",
    year = "1966",
    journal = "Nature",
    url = "https://doi.org/10.1038/2121193a0",
    doi = "10.1038/2121193a0",
    openalex = "W2095054686"
}

@article{black1967cosmic,
    author = "Black, D.I.",
    title = "Cosmic ray effects and faunal extinctions at geomagnetic field reversals",
    year = "1967",
    journal = "Earth and Planetary Science Letters",
    url = "https://doi.org/10.1016/0012-821x(67)90042-8",
    doi = "10.1016/0012-821x(67)90042-8",
    openalex = "W2055198203",
    pages = "225-236",
    volume = "3",
    references = "doi101001jama196603100230164053, doi101029jz069i001p00013, doi101029jz071i019p04469, doi101029jz072i010p02603, doi101029rg001i001p00035, doi10106313060570, doi10111911934186, doi101126science1543747349, openalexw2171582839, openalexw2978227140"
}

@article{doi101029jz072i012p03247,
    author = "Coe, Robert S.",
    title = "Paleo-intensities of the Earth's magnetic field determined from Tertiary and Quaternary rocks",
    year = "1967",
    journal = "Journal of Geophysical Research Atmospheres",
    url = "https://doi.org/10.1029/jz072i012p03247",
    doi = "10.1029/jz072i012p03247",
    openalex = "W2015133676"
}

Paleomagnetic polarity changes have been detected in nine deep-sea sedimentary cores (from the Pacific-Antarctic Basin) in which an extinction horizon of a radiolarian assemblage was previously independently determined. The depths of the polarity change 0.7 million years ago and the faunal boundary are closely correlated, confirming that the faunal extinction was locally virtually synchronous. Although the reason for the faunal extinction is unknown. the possibility of causal relationships between faunal extinction and factors directly involved with sedimentation rate, sedimentation rate variation, and sediment type appears to be excluded.

@article{doi101126science15637781083,
    author = "Watkins, N. D. and Goodell, H",
    title = "Geomagnetic Polarity Change and Faunal Extinction in the Southern Ocean",
    year = "1967",
    journal = "Science",
    abstract = "Paleomagnetic polarity changes have been detected in nine deep-sea sedimentary cores (from the Pacific-Antarctic Basin) in which an extinction horizon of a radiolarian assemblage was previously independently determined. The depths of the polarity change 0.7 million years ago and the faunal boundary are closely correlated, confirming that the faunal extinction was locally virtually synchronous. Although the reason for the faunal extinction is unknown. the possibility of causal relationships between faunal extinction and factors directly involved with sedimentation rate, sedimentation rate variation, and sediment type appears to be excluded.",
    url = "https://doi.org/10.1126/science.156.3778.1083",
    doi = "10.1126/science.156.3778.1083",
    openalex = "W2074586846"
}

95 NRM-TRM curves were determined by Thellier's method from a variety of volcanic rocks. Most of them deviate from a straight line over parts of their length, sometimes so much that not even a crude estimate of paleo-intensity can be made. Some of the many possible causes of such non-ideal behavior include the effects of the sample demagnetizing field, secondary components of magnetization, mechanisms of acquisition of TRM which violate the assumptions of Thellier's method (such as nonlinearity of TRM with field), changes in the TRM spectrum induced by heating in the laboratory, and others. Where possible these mechanisms are discussed from both a theoretical and experimental standpoint, and their effects are identified in the NRM-TRM curves. In addition, diagnostic tests designed to determine quickly the suitability of a rock for intensity studies were sought. Tests tried included the comparison of heating and cooling Js-T curves, measurement of susceptibility before and after heating, and others. None were adequate. Finally, the quicker method of simply comparing the NRM and the total TRM is compared with Thellier's method for determining paleo-intensities. The latter is clearly the more informative and reliable when dealing with individual units, but the former may be useful for deriving average values of the paleo-intensity during geologic periods from large suites of volcanic rocks of varying types.

@article{doi105636jgg19157,
    author = "Coe, Robert S.",
    title = "The Determination of Paleo-Intensities of the Earth's Magnetic Field with Emphasis on Mechanisms which Could Cause Non-ideal Behavior in Thellier's Method",
    year = "1967",
    journal = "Journal of geomagnetism and geoelectricity",
    abstract = "95 NRM-TRM curves were determined by Thellier's method from a variety of volcanic rocks. Most of them deviate from a straight line over parts of their length, sometimes so much that not even a crude estimate of paleo-intensity can be made. Some of the many possible causes of such non-ideal behavior include the effects of the sample demagnetizing field, secondary components of magnetization, mechanisms of acquisition of TRM which violate the assumptions of Thellier's method (such as nonlinearity of TRM with field), changes in the TRM spectrum induced by heating in the laboratory, and others. Where possible these mechanisms are discussed from both a theoretical and experimental standpoint, and their effects are identified in the NRM-TRM curves. In addition, diagnostic tests designed to determine quickly the suitability of a rock for intensity studies were sought. Tests tried included the comparison of heating and cooling Js-T curves, measurement of susceptibility before and after heating, and others. None were adequate. Finally, the quicker method of simply comparing the NRM and the total TRM is compared with Thellier's method for determining paleo-intensities. The latter is clearly the more informative and reliable when dealing with individual units, but the former may be useful for deriving average values of the paleo-intensity during geologic periods from large suites of volcanic rocks of varying types.",
    url = "https://doi.org/10.5636/jgg.19.157",
    doi = "10.5636/jgg.19.157",
    openalex = "W2007631062"
}

This paper summarizes the results of the three previous papers in this series, which have shown the presence of a pattern of magnetic anomalies, bilaterally symmetric about the crest of the ridge in the Pacific, Atlantic, and Indian oceans. By assuming that the pattern is caused by a sequence of normally and reversely magnetized blocks that have been produced by sea floor spreading at the axes of the ridges, it is shown that the sequences of blocks correspond to the same geomagnetic time scale. An attempt is made to determine the absolute ages of this time scale using palcomagnetic and paleontological data. The pattern of opening of the oceans is discussed and the implications on continental drift are considered. This pattern is in good agreement with continental drift, in particular with the history of the break up of Gondwanaland.

@article{doi101029jb073i006p02119,
    author = "Heirtzler, J. R. and Dickson, G. O. and Herron, E. M. and Pitman, Walter C. and Pichon, Xavier Le",
    title = "Marine magnetic anomalies, geomagnetic field reversals, and motions of the ocean floor and continents",
    year = "1968",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "This paper summarizes the results of the three previous papers in this series, which have shown the presence of a pattern of magnetic anomalies, bilaterally symmetric about the crest of the ridge in the Pacific, Atlantic, and Indian oceans. By assuming that the pattern is caused by a sequence of normally and reversely magnetized blocks that have been produced by sea floor spreading at the axes of the ridges, it is shown that the sequences of blocks correspond to the same geomagnetic time scale. An attempt is made to determine the absolute ages of this time scale using palcomagnetic and paleontological data. The pattern of opening of the oceans is discussed and the implications on continental drift are considered. This pattern is in good agreement with continental drift, in particular with the history of the break up of Gondwanaland.",
    url = "https://doi.org/10.1029/jb073i006p02119",
    doi = "10.1029/jb073i006p02119",
    openalex = "W2027477351",
    references = "doi101029jb073i006p01959, doi101029jb073i012p03661, doi101029jz072i008p02131, doi101038190854a0, doi101038199947a0, doi101038207343a0, doi101126science15437531164, doi101126science15437551405, doi101130petrologic1962599, openalexw2978227140, sykes1967mechanism"
}

@article{doi101038217046a0,
    author = "Harrison, C. G. A.",
    title = "Evolutionary Processes and Reversals of the Earth's Magnetic Field",
    year = "1968",
    journal = "Nature",
    url = "https://doi.org/10.1038/217046a0",
    doi = "10.1038/217046a0",
    openalex = "W2074054503"
}

Abstract This paper is an account of the Bakerian Lecture given to the Royal Society on 15 June 1967. Reversals of the Earth’s magnetic field can be studied in the magnetization of lavas and sediments on land, in the magnetization of deep sea cores and in the magnetic pattern on the ocean floor. The lavas give radiometric dates but not a continuous sequence; the cores give continuity, great detail and a resolution as fine as 1000 years; the magnetic pattern gives information all through the Tertiary and connects the spreading of the ocean floor with the radiometric time scale. The dynamo theory of the Earth’s magnetic field may be able to account for reversals as an instability in the dynamo, but only models with a finite number of degrees of freedom have been investigated. Spreading of the ocean floor is believed to be associated with convective motions in the upper mantle, although there are difficulties connected with the equality of the oceanic and continental heat flows. There is some evidence for the extinction of radiolaria at times of reversal of the magnetic field; it has been suggested that this is due to the effect of the field on cosmic rays but this appears impossible. If the extinctions are due to the reversals, the mechanism is unknown. Reversely magnetized rocks are more highly oxidized than normally magnetized ones. The cause of this is unknown and is one of the outstanding problems of Earth science.

@article{doi101098rsta19680031,
    author = "Bullard, E. C.",
    title = "The Bakerian lecture, 1967 reversals of the Earth's magnetic field",
    year = "1968",
    journal = "Philosophical Transactions of the Royal Society of London Series A Mathematical and Physical Sciences",
    abstract = "Abstract This paper is an account of the Bakerian Lecture given to the Royal Society on 15 June 1967. Reversals of the Earth’s magnetic field can be studied in the magnetization of lavas and sediments on land, in the magnetization of deep sea cores and in the magnetic pattern on the ocean floor. The lavas give radiometric dates but not a continuous sequence; the cores give continuity, great detail and a resolution as fine as 1000 years; the magnetic pattern gives information all through the Tertiary and connects the spreading of the ocean floor with the radiometric time scale. The dynamo theory of the Earth’s magnetic field may be able to account for reversals as an instability in the dynamo, but only models with a finite number of degrees of freedom have been investigated. Spreading of the ocean floor is believed to be associated with convective motions in the upper mantle, although there are difficulties connected with the equality of the oceanic and continental heat flows. There is some evidence for the extinction of radiolaria at times of reversal of the magnetic field; it has been suggested that this is due to the effect of the field on cosmic rays but this appears impossible. If the extinctions are due to the reversals, the mechanism is unknown. Reversely magnetized rocks are more highly oxidized than normally magnetized ones. The cause of this is unknown and is one of the outstanding problems of Earth science.",
    url = "https://doi.org/10.1098/rsta.1968.0031",
    doi = "10.1098/rsta.1968.0031",
    openalex = "W2056709938",
    references = "black1967cosmic, doi101029jb073i006p02119, doi101038190854a0, doi101038199947a0, doi1010382161276a0, doi10106313058072, doi101086147060, doi101098rsta19650020, doi101126science15437551405, openalexw2307523182, sykes1967mechanism"
}

@article{hays1971faunal,
    author = "HAYS, JAMES D.",
    title = "Faunal Extinctions and Reversals of the Earth's Magnetic Field",
    year = "1971",
    journal = "Geological Society of America Bulletin",
    url = "https://doi.org/10.1130/0016-7606(1971)82[2433:fearot]2.0.co;2",
    doi = "10.1130/0016-7606(1971)82[2433:fearot]2.0.co;2",
    number = "9",
    openalex = "W2109522189",
    pages = "2433",
    volume = "82"
}

@techreport{hays1971faunal2,
    author = "Hays, J. D",
    title = "Faunal extinctions and reversals of the earth's magnetic field",
    year = "1971",
    howpublished = "Geological Society of America Bulletin, v. 82, p. 2433-2447",
    note = "talkorigins\_source = {true}; raw\_reference = {Hays, J. D., 1971, Faunal extinctions and reversals of the earth's magnetic field: Geological Society of America Bulletin, v. 82, p. 2433-2447.}"
}

@article{hays1972faunal,
    author = "HAYS, JAMES D.",
    title = "Faunal Extinctions and Reversals of the Earth's Magnetic Field: Reply",
    year = "1972",
    journal = "Geological Society of America Bulletin",
    url = "https://doi.org/10.1130/0016-7606(1972)83[2215:fearot]2.0.co;2",
    doi = "10.1130/0016-7606(1972)83[2215:fearot]2.0.co;2",
    number = "7",
    openalex = "W4250146624",
    pages = "2215",
    volume = "83"
}

@article{mann1972faunal,
    author = "MANN, C. JOHN",
    title = "Faunal Extinctions and Reversals of the Earth's Magnetic Field: Discussion",
    year = "1972",
    journal = "Geological Society of America Bulletin",
    url = "https://doi.org/10.1130/0016-7606(1972)83[2211:fearot]2.0.co;2",
    doi = "10.1130/0016-7606(1972)83[2211:fearot]2.0.co;2",
    number = "7",
    openalex = "W2000787067",
    pages = "2211",
    volume = "83"
}

@article{crossref1973earth,
    title = "Earth' Magnetic Field: Dipolar Reversals",
    year = "1973",
    journal = "Nature",
    url = "https://doi.org/10.1038/245185a0",
    doi = "10.1038/245185a0",
    number = "5422",
    openalex = "W4247608168",
    pages = "185-185",
    volume = "245"
}

@article{doi1010160370157376900065,
    author = "Jacobs, J. A.",
    title = "Reversals of the earth's magnetic field",
    year = "1976",
    journal = "Physics Reports",
    url = "https://doi.org/10.1016/0370-1573(76)90006-5",
    doi = "10.1016/0370-1573(76)90006-5",
    openalex = "W2075017721",
    references = "doi101098rsta19680031"
}

@misc{eberhart1976of1,
    author = "Eberhart, J",
    title = "Of life and death and magnetism",
    year = "1976",
    howpublished = "Science News, v. 109, p. 204",
    note = "talkorigins\_source = {true}; raw\_reference = {Eberhart, J., 1976, Of life and death and magnetism: Science News, v. 109, p. 204.}"
}

Synthetic reversal records for different latitudes have been generated for model transition fields with various zonal harmonic contents. The model fields are based upon a redistribution of energy from an exponential decay of the dipole field to g 2 °, g 3 °, and g 4 °.The records emphasize the dependence of their characteristics upon the latitude of the observation site. Both intensity and inclination changes, the relationship between these two aspects of the records, and estimates of the time to complete the reversal are all strongly dependent upon latitude. A particular model in which the dipole energy is redistributed to g 2 °, g 3 ° and g 4 ° according to the ratio 2:3:5 is used to simulate the last reversal.

@article{doi101029jb086ib12p11657,
    author = "Williams, Ian S. and Fuller, M.",
    title = "Zonal harmonic models of reversal transition fields",
    year = "1981",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Synthetic reversal records for different latitudes have been generated for model transition fields with various zonal harmonic contents. The model fields are based upon a redistribution of energy from an exponential decay of the dipole field to g 2 °, g 3 °, and g 4 °.The records emphasize the dependence of their characteristics upon the latitude of the observation site. Both intensity and inclination changes, the relationship between these two aspects of the records, and estimates of the time to complete the reversal are all strongly dependent upon latitude. A particular model in which the dipole energy is redistributed to g 2 °, g 3 ° and g 4 ° according to the ratio 2:3:5 is used to simulate the last reversal.",
    url = "https://doi.org/10.1029/jb086ib12p11657",
    doi = "10.1029/jb086ib12p11657",
    openalex = "W2009580186",
    references = "doi101098rsta19680031"
}

A deep-sea core from the Caribbean contains a layer of sediment highly enriched in meteoritic iridium. This layer underlies a layer of North American microtektites dated at 34.4 million years ago and coincides with the extinction of five major species of Radiolaria. It is suggested that a massive, chemically undifferentiated meteorite collided with the earth, producing the tektites and leading to extinctions 34 million years ago.

@article{doi101126science2164548885,
    author = "Ganapathy, R.",
    title = "Evidence for a Major Meteorite Impact on the Earth 34 Million Years Ago: Implication for Eocene Extinctions",
    year = "1982",
    journal = "Science",
    abstract = "A deep-sea core from the Caribbean contains a layer of sediment highly enriched in meteoritic iridium. This layer underlies a layer of North American microtektites dated at 34.4 million years ago and coincides with the extinction of five major species of Radiolaria. It is suggested that a massive, chemically undifferentiated meteorite collided with the earth, producing the tektites and leading to extinctions 34 million years ago.",
    url = "https://doi.org/10.1126/science.216.4548.885",
    doi = "10.1126/science.216.4548.885",
    openalex = "W2004264006"
}

@article{crossref1985magnetic,
    title = "Magnetic reversals and mass extinctions",
    year = "1985",
    journal = "Deep Sea Research Part B. Oceanographic Literature Review",
    url = "https://doi.org/10.1016/0198-0254(85)93060-2",
    doi = "10.1016/0198-0254(85)93060-2",
    number = "9",
    openalex = "W4240305065",
    pages = "777-778",
    volume = "32"
}

@article{doi101038314341a0,
    author = "Raup, David M.",
    title = "Magnetic reversals and mass extinctions",
    year = "1985",
    journal = "Nature",
    url = "https://doi.org/10.1038/314341a0",
    doi = "10.1038/314341a0",
    openalex = "W2000297916",
    references = "alvarez1980extraterrestrial, doi101029gl010i008p00713, doi101029jb089ib05p03354, doi101038308709a0, doi101038308718a0, doi101073pnas813801, doi101126science22346411135, doi101126science2264673437, doi101126science22646811427, hays1971faunal, openalexw2989049194"
}

The impact of a large extraterrestrial object on the Earth can produce a geomagnetic reversal through the following mechanism: dust from the impact crater and soot from fires trigger a climate change and the beginning of a little ice age. The redistribution of water near the equator to ice at high latitudes alters the rotation rate of the crust and mantle of the Earth. If the sea‐level change is sufficiently large (>10 meters) and rapid (in a few hundred years), then the velocity shear in the liquid core disrupts the convective cells that drive the dynamo. The new convective cells that subsequently form distort and tangle the previous field, reducing the dipole component near to zero while increasing the energy in multipole components. Eventually a dipole is rebuilt by dynamo action, and the event is seen either as a geomagnetic reversal or as an excursion. Sudden climate changes from other causes such as volcanic eruptions could also trigger reversals. This mechanism may not be the sole cause of geomagnetic reversals, but it can account for the rapid drop of the dipole component preceding a reversal, the predominance of multipole components during a transition, the associations of microtektites, temperature drops and extinctions with reversals, and the possible correlation between peaks in the geomagnetic reversal rate and the times of mass extinctions. The model may also account for the long‐term changes in the average rate of reversals. We make several testable predictions.

@article{doi101029gl013i011p01177,
    author = "Muller, Richard A. and Morris, Donald E.",
    title = "Geomagnetic reversals from impacts on the Earth",
    year = "1986",
    journal = "Geophysical Research Letters",
    abstract = "The impact of a large extraterrestrial object on the Earth can produce a geomagnetic reversal through the following mechanism: dust from the impact crater and soot from fires trigger a climate change and the beginning of a little ice age. The redistribution of water near the equator to ice at high latitudes alters the rotation rate of the crust and mantle of the Earth. If the sea‐level change is sufficiently large (>10 meters) and rapid (in a few hundred years), then the velocity shear in the liquid core disrupts the convective cells that drive the dynamo. The new convective cells that subsequently form distort and tangle the previous field, reducing the dipole component near to zero while increasing the energy in multipole components. Eventually a dipole is rebuilt by dynamo action, and the event is seen either as a geomagnetic reversal or as an excursion. Sudden climate changes from other causes such as volcanic eruptions could also trigger reversals. This mechanism may not be the sole cause of geomagnetic reversals, but it can account for the rapid drop of the dipole component preceding a reversal, the predominance of multipole components during a transition, the associations of microtektites, temperature drops and extinctions with reversals, and the possible correlation between peaks in the geomagnetic reversal rate and the times of mass extinctions. The model may also account for the long‐term changes in the average rate of reversals. We make several testable predictions.",
    url = "https://doi.org/10.1029/gl013i011p01177",
    doi = "10.1029/gl013i011p01177",
    openalex = "W2027303276",
    references = "alvarez1980extraterrestrial, crossref1982geological, doi1010160033589474900076, doi101038314341a0, doi101073pnas813801, doi101098rsta19500014, doi101126science19442701121, doi101306m26490, doi102973dsdpproc291171975, hays1971faunal, openalexw1521644843, openalexw3160761443"
}

True polar wander, the shifting of the entire mantle relative to the earth's spin axis, has been reanalyzed. Over the last 200 million years, true polar wander has been fast (approximately 5 centimeters per year) most of the time, except for a remarkable standstill from 170 to 110 million years ago. This standstill correlates with a decrease in the reversal frequency of the geomagnetic field and episodes of continental breakup. Conversely, true polar wander is high when reversal frequency increases. It is proposed that intermittent convection modulates the thickness of a thermal boundary layer at the base of the mantle and consequently the core-to-mantle heat flux. Emission of hot thermals from the boundary layer leads to increases in mantle convection and true polar wander. In conjunction, cold thermals released from a boundary layer at the top of the liquid core eventually lead to reversals. Changes in the locations of subduction zones may also affect true polar wander. Exceptional volcanism and mass extinctions at the Cretaceous-Tertiary and Permo-Triassic boundaries may be related to thermals released after two unusually long periods with no magnetic reversals. These environmental catastrophes may therefore be a consequence of thermal and chemical couplings in the earth's multilayer heat engine rather than have an extraterrestrial cause.

@article{doi101126science23748191140,
    author = "Courtillot, Vincent and Besse, Jean",
    title = "Magnetic Field Reversals, Polar Wander, and Core-Mantle Coupling",
    year = "1987",
    journal = "Science",
    abstract = "True polar wander, the shifting of the entire mantle relative to the earth's spin axis, has been reanalyzed. Over the last 200 million years, true polar wander has been fast (approximately 5 centimeters per year) most of the time, except for a remarkable standstill from 170 to 110 million years ago. This standstill correlates with a decrease in the reversal frequency of the geomagnetic field and episodes of continental breakup. Conversely, true polar wander is high when reversal frequency increases. It is proposed that intermittent convection modulates the thickness of a thermal boundary layer at the base of the mantle and consequently the core-to-mantle heat flux. Emission of hot thermals from the boundary layer leads to increases in mantle convection and true polar wander. In conjunction, cold thermals released from a boundary layer at the top of the liquid core eventually lead to reversals. Changes in the locations of subduction zones may also affect true polar wander. Exceptional volcanism and mass extinctions at the Cretaceous-Tertiary and Permo-Triassic boundaries may be related to thermals released after two unusually long periods with no magnetic reversals. These environmental catastrophes may therefore be a consequence of thermal and chemical couplings in the earth's multilayer heat engine rather than have an extraterrestrial cause.",
    url = "https://doi.org/10.1126/science.237.4819.1140",
    doi = "10.1126/science.237.4819.1140",
    openalex = "W2060453905",
    references = "doi101029eo067i035p00649, doi101029jb091ib11p11519, doi101038314341a0, doi101038326143a0, doi101126science22746911161"
}

@article{loper1988a,
    author = "Loper, David E. and McCartney, Kevin and Buzyna, George",
    title = "A Model of Correlated Episodicity in Magnetic-Field Reversals, Climate, and Mass Extinctions",
    year = "1988",
    journal = "The Journal of Geology",
    url = "https://doi.org/10.1086/629189",
    doi = "10.1086/629189",
    number = "1",
    openalex = "W1972274221",
    pages = "1-15",
    volume = "96",
    references = "alvarez1980extraterrestrial, doi1010160012821x86901184, doi101029jb080i005p00705, doi101038230042a0, doi101073pnas813801, doi101126science21545391501, doi101126science23547931156, doi101130mem132p7, doi1011751520046919750320003teodtc20co2, doi101306m26490c6"
}

Analysis of the fossil record of microbes, algae, fungi, protists, plants, and animals shows that the diversity of both marine and continental life increased exponentially since the end of the Precambrian. This diversification was interrupted by mass extinctions, the largest of which occurred in the Early Cambrian, Late Ordovician, Late Devonian, Late Permian, Early Triassic, Late Triassic, and end-Cretaceous. Most of these extinctions were experienced by both marine and continental organisms. As for the periodicity of mass extinctions, no support was found: Seven mass extinction peaks in the last 250 million years are spaced 20 to 60 million years apart.

@article{doi101126science7701342,
    author = "Benton, Michael J.",
    title = "Diversification and Extinction in the History of Life",
    year = "1995",
    journal = "Science",
    abstract = "Analysis of the fossil record of microbes, algae, fungi, protists, plants, and animals shows that the diversity of both marine and continental life increased exponentially since the end of the Precambrian. This diversification was interrupted by mass extinctions, the largest of which occurred in the Early Cambrian, Late Ordovician, Late Devonian, Late Permian, Early Triassic, Late Triassic, and end-Cretaceous. Most of these extinctions were experienced by both marine and continental organisms. As for the periodicity of mass extinctions, no support was found: Seven mass extinction peaks in the last 250 million years are spaced 20 to 60 million years apart.",
    url = "https://doi.org/10.1126/science.7701342",
    doi = "10.1126/science.7701342",
    openalex = "W2010154591",
    references = "doi1010029781444313918, doi101017s0094837300005972, doi101017s0094837300006539, doi101017s0094837300008186, doi101038293435a0, doi101038303614a0, doi101073pnas813801, doi101111j109600311988tb00514x, doi101111j155856461987tb02459x, doi101126science11536548, doi101126science13334591105, doi101126science17740541065, doi101126science21545391501, doi101126science2605108640, doi1023072409086, doi105860choice284524, openalexw1599677799, openalexw2989049194"
}

@article{doi10103820420,
    author = "Guyodo, Yohan and Valet, Jean‐Pierre",
    title = "Global changes in intensity of the Earth's magnetic field during the past 800 kyr",
    year = "1999",
    journal = "Nature",
    url = "https://doi.org/10.1038/20420",
    doi = "10.1038/20420",
    openalex = "W1556482552"
}

@incollection{crossref2000magnetic,
    title = "Magnetic Field Reversals",
    year = "2000",
    booktitle = "International Geophysics",
    url = "https://doi.org/10.1016/s0074-6142(00)80097-2",
    doi = "10.1016/s0074-6142(00)80097-2",
    openalex = "W4229682381",
    pages = "137-182"
}

Four magnetic polarity reversals that occurred during two numerical simulations of the Glatzmaier–Roberts geodynamo display a range of behaviour that resembles records of real reversals of the Earth‘s magnetic field in some ways, and suggests additional insights in others. Two reversals happened during the homogeneous simulation, which prescribes spatially uniform heat flux at the core–mantle boundary (CMB); and two occurred during the tomographic simulation, which specifies variable CMB heat flux patterned after a low–order seismic velocity model from tomographic investigation of the lower mantle. All but one were accomplished within 2000–7000 (model) years, whereas the second tomographic reversal took 22 000 years. The two homogeneous transitions display low intensities typical of real reversals, with longer–term variation resembling what has been called ‘sawtooth’ behaviour. During the first tomographic reversal extremely high non–dipole fields occur in some regions, the result of strong patches of vertical flux that appear in less than 100 years and grow rapidly for several hundred more. The intensity during the second tomographic reversal is unusually low for a long time, and large–amplitude oscillations in direction are common. The fields in the middle of the polarity transitions are dominantly non–dipolar for all but the first tomographic reversal. One consists of spherical harmonics that are mainly antisymmetric about the equator, two by symmetric harmonics, and one by a mixture of symmetric and antisymmetric harmonics. Despite this wide variety of characteristics, all reversals occur when the non–dipole energy trend is upward. Finally, after running 300 kyr and reversing twice, the density of transitional virtual geomagnetic poles in the tomographic simulations exhibits a crude statistical correlation with areas of higher–than–average CMB heat flux, offering some support for hypotheses of preferred bands and patches.

@article{doi101098rsta20000578,
    author = "Coe, Robert S. and Hongre, Lionel and Glatzmaier, Gary A.",
    title = "An examination of simulated geomagnetic reversals from a palaeomagnetic perspective",
    year = "2000",
    journal = "Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences",
    abstract = "Four magnetic polarity reversals that occurred during two numerical simulations of the Glatzmaier–Roberts geodynamo display a range of behaviour that resembles records of real reversals of the Earth‘s magnetic field in some ways, and suggests additional insights in others. Two reversals happened during the homogeneous simulation, which prescribes spatially uniform heat flux at the core–mantle boundary (CMB); and two occurred during the tomographic simulation, which specifies variable CMB heat flux patterned after a low–order seismic velocity model from tomographic investigation of the lower mantle. All but one were accomplished within 2000–7000 (model) years, whereas the second tomographic reversal took 22 000 years. The two homogeneous transitions display low intensities typical of real reversals, with longer–term variation resembling what has been called ‘sawtooth’ behaviour. During the first tomographic reversal extremely high non–dipole fields occur in some regions, the result of strong patches of vertical flux that appear in less than 100 years and grow rapidly for several hundred more. The intensity during the second tomographic reversal is unusually low for a long time, and large–amplitude oscillations in direction are common. The fields in the middle of the polarity transitions are dominantly non–dipolar for all but the first tomographic reversal. One consists of spherical harmonics that are mainly antisymmetric about the equator, two by symmetric harmonics, and one by a mixture of symmetric and antisymmetric harmonics. Despite this wide variety of characteristics, all reversals occur when the non–dipole energy trend is upward. Finally, after running 300 kyr and reversing twice, the density of transitional virtual geomagnetic poles in the tomographic simulations exhibits a crude statistical correlation with areas of higher–than–average CMB heat flux, offering some support for hypotheses of preferred bands and patches.",
    url = "https://doi.org/10.1098/rsta.2000.0578",
    doi = "10.1098/rsta.2000.0578",
    openalex = "W2123259125",
    references = "doi101029gl013i011p01177"
}

Young loggerhead sea turtles (Caretta caretta) from eastern Florida undertake a transoceanic migration in which they gradually circle the north Atlantic Ocean before returning to the North American coast. Here we report that hatchling loggerheads, when exposed to magnetic fields replicating those found in three widely separated oceanic regions, responded by swimming in directions that would, in each case, help keep turtles within the currents of the North Atlantic gyre and facilitate movement along the migratory pathway. These results imply that young loggerheads have a guidance system in which regional magnetic fields function as navigational markers and elicit changes in swimming direction at crucial geographic boundaries.

@article{doi101126science1064557,
    author = "Lohmann, Kenneth J. and Cain, Shaun D. and Dodge, Susan A. and Lohmann, Catherine M. F.",
    title = "Regional Magnetic Fields as Navigational Markers for Sea Turtles",
    year = "2001",
    journal = "Science",
    abstract = "Young loggerhead sea turtles (Caretta caretta) from eastern Florida undertake a transoceanic migration in which they gradually circle the north Atlantic Ocean before returning to the North American coast. Here we report that hatchling loggerheads, when exposed to magnetic fields replicating those found in three widely separated oceanic regions, responded by swimming in directions that would, in each case, help keep turtles within the currents of the North Atlantic gyre and facilitate movement along the migratory pathway. These results imply that young loggerheads have a guidance system in which regional magnetic fields function as navigational markers and elicit changes in swimming direction at crucial geographic boundaries.",
    url = "https://doi.org/10.1126/science.1064557",
    doi = "10.1126/science.1064557",
    openalex = "W2019330298",
    references = "doi10100797814613031383"
}

The evolution of life is affected by variations of atmospheric oxygen level and geomagnetic field intensity. Oxygen can escape into interplanetary space as ions after gaining momentum from solar wind, but Earth's strong dipole field reduces the momentum transfer efficiency and the ion outflow rate, except for the time of geomagnetic polarity reversals when the field is significantly weakened in strength and becomes Mars-like in morphology. The newest databases available for the Phanerozoic era illustrate that the reversal rate increased and the atmospheric oxygen level decreased when the marine diversity showed a gradual pattern of mass extinctions lasting millions of years. We propose that accumulated oxygen escape during an interval of increased reversal rate could have led to the catastrophic drop of oxygen level, which is known to be a cause of mass extinction. We simulated the oxygen ion escape rate for the Triassic–Jurassic event, using a modified Martian ion escape model with an input of quiet solar wind inferred from Sun-like stars. The results show that geomagnetic reversal could enhance the oxygen escape rate by 3–4 orders only if the magnetic field was extremely weak, even without consideration of space weather effects. This suggests that our hypothesis could be a possible explanation of a correlation between geomagnetic reversals and mass extinction. Therefore, if this causal relation indeed exists, it should be a “many-to-one” scenario rather the previously considered “one-to-one”, and planetary magnetic field should be much more important than previously thought for planetary habitability.

@article{doi101016jepsl201403018,
    author = "Wei, Yong and Pu, Z. Y. and Zong, Qiugang and Wan, Weixing and Ren, Zhipeng and Fräenz, M. and Dubinin, E. and Tian, Feng and Shi, Quanqi and Fu, Suiyan and Hong, Minghua",
    title = "Oxygen escape from the Earth during geomagnetic reversals: Implications to mass extinction",
    year = "2014",
    journal = "Earth and Planetary Science Letters",
    abstract = "The evolution of life is affected by variations of atmospheric oxygen level and geomagnetic field intensity. Oxygen can escape into interplanetary space as ions after gaining momentum from solar wind, but Earth's strong dipole field reduces the momentum transfer efficiency and the ion outflow rate, except for the time of geomagnetic polarity reversals when the field is significantly weakened in strength and becomes Mars-like in morphology. The newest databases available for the Phanerozoic era illustrate that the reversal rate increased and the atmospheric oxygen level decreased when the marine diversity showed a gradual pattern of mass extinctions lasting millions of years. We propose that accumulated oxygen escape during an interval of increased reversal rate could have led to the catastrophic drop of oxygen level, which is known to be a cause of mass extinction. We simulated the oxygen ion escape rate for the Triassic–Jurassic event, using a modified Martian ion escape model with an input of quiet solar wind inferred from Sun-like stars. The results show that geomagnetic reversal could enhance the oxygen escape rate by 3–4 orders only if the magnetic field was extremely weak, even without consideration of space weather effects. This suggests that our hypothesis could be a possible explanation of a correlation between geomagnetic reversals and mass extinction. Therefore, if this causal relation indeed exists, it should be a “many-to-one” scenario rather the previously considered “one-to-one”, and planetary magnetic field should be much more important than previously thought for planetary habitability.",
    url = "https://doi.org/10.1016/j.epsl.2014.03.018",
    doi = "10.1016/j.epsl.2014.03.018",
    openalex = "W2064186232",
    references = "doi101007s1121401096596"
}

The temporal link between mass extinctions and large igneous provinces is well known. Here, we examine this link by focusing on the potential climatic effects of large igneous province eruptions during several extinction crises that show the best correlation with mass volcanism: the Frasnian-Famennian (Late Devonian), Capitanian (Middle Permian), end-Permian, end-Triassic, and Toarcian (Early Jurassic) extinctions. It is clear that there is no direct correlation between total volume of lava and extinction magnitude because there is always sufficient recovery time between individual eruptions to negate any cumulative effect of successive flood basalt eruptions. Instead, the environmental and climatic damage must be attributed to single-pulse gas effusions. It is notable that the best-constrained examples of death-by-volcanism record the main extinction pulse at the onset of (often explosive) volcanism (e.g., the Capitanian, end-Permian, and end-Triassic examples), suggesting that the rapid injection of vast quantities of volcanic gas (CO 2 and SO 2) is the trigger for a truly major biotic catastrophe. Warming and marine anoxia feature in many extinction scenarios, indicating that the ability of a large igneous province to induce these proximal killers (from CO 2 emissions and thermogenic greenhouse gases) is the single most important factor governing its lethality. Intriguingly, many voluminous large igneous province eruptions, especially those of the Cretaceous oceanic plateaus, are not associated with significant extinction losses. This suggests that the link between the two phenomena may be controlled by a range of factors, including continental configuration, the latitude, volume, rate, and duration of eruption, its style and setting (continental vs. oceanic), the preexisting climate state, and the resilience of the extant biota to change.

@incollection{doi1011302014250502,
    author = "Bond, David P.G. and Wignall, Paul B.",
    title = "Large igneous provinces and mass extinctions: An update",
    year = "2014",
    booktitle = "Geological Society of America eBooks",
    abstract = "The temporal link between mass extinctions and large igneous provinces is well known. Here, we examine this link by focusing on the potential climatic effects of large igneous province eruptions during several extinction crises that show the best correlation with mass volcanism: the Frasnian-Famennian (Late Devonian), Capitanian (Middle Permian), end-Permian, end-Triassic, and Toarcian (Early Jurassic) extinctions. It is clear that there is no direct correlation between total volume of lava and extinction magnitude because there is always sufficient recovery time between individual eruptions to negate any cumulative effect of successive flood basalt eruptions. Instead, the environmental and climatic damage must be attributed to single-pulse gas effusions. It is notable that the best-constrained examples of death-by-volcanism record the main extinction pulse at the onset of (often explosive) volcanism (e.g., the Capitanian, end-Permian, and end-Triassic examples), suggesting that the rapid injection of vast quantities of volcanic gas (CO 2 and SO 2) is the trigger for a truly major biotic catastrophe. Warming and marine anoxia feature in many extinction scenarios, indicating that the ability of a large igneous province to induce these proximal killers (from CO 2 emissions and thermogenic greenhouse gases) is the single most important factor governing its lethality. Intriguingly, many voluminous large igneous province eruptions, especially those of the Cretaceous oceanic plateaus, are not associated with significant extinction losses. This suggests that the link between the two phenomena may be controlled by a range of factors, including continental configuration, the latitude, volume, rate, and duration of eruption, its style and setting (continental vs. oceanic), the preexisting climate state, and the resilience of the extant biota to change.",
    url = "https://doi.org/10.1130/2014.2505(02)",
    doi = "10.1130/2014.2505(02)",
    openalex = "W2187825126",
    references = "doi101016001670379290334f, doi101016jgeobios201111001, doi101016s0012825200000374, doi1010291998rg000054, doi10102993rg02508, doi101038227930a0, doi101038nature02566, doi101126science1097403, doi101126science1224126, doi101126science21545391501, doi101126science27252651155, doi10113000167606"
}

Polarity reversals of the geomagnetic field are a major feature of the Earth's dynamo. Questions remain regarding the dynamical processes that give rise to reversals and the properties of the geomagnetic field during a polarity transition. A large number of paleomagnetic reversal records have been acquired during the past 50 years in order to better constrain the structure and geometry of the transitional field. In addition, over the past two decades, numerical dynamo simulations have also provided insights into the reversal mechanism. Yet despite the large paleomagnetic database, controversial interpretations of records of the transitional field persist; they result from two characteristics inherent to all reversals, both of which are detrimental to an ambiguous analysis. On the one hand, the reversal process is rapid and requires adequate temporal resolution. On the other hand, weak field intensities during a reversal can affect the fidelity of magnetic recording in sedimentary records. This paper is aimed at reviewing critically the main reversal features derived from paleomagnetic records and at analyzing some of these features in light of numerical simulations. We discuss in detail the fidelity of the signal extracted from paleomagnetic records and pay special attention to their resolution with respect to the timing and mechanisms involved in the magnetization process. Records from marine sediments dominate the database. They give rise to transitional field models that often lead to overinterpret the data. Consequently, we attempt to separate robust results (and their subsequent interpretations) from those that do not stand on a strong observational footing. Finally, we discuss new avenues that should favor progress to better characterize and understand transitional field behavior.

@article{doi1010022015rg000506,
    author = "Valet, Jean‐Pierre and Fournier, Alexandre",
    title = "Deciphering records of geomagnetic reversals",
    year = "2016",
    journal = "Reviews of Geophysics",
    abstract = "Polarity reversals of the geomagnetic field are a major feature of the Earth's dynamo. Questions remain regarding the dynamical processes that give rise to reversals and the properties of the geomagnetic field during a polarity transition. A large number of paleomagnetic reversal records have been acquired during the past 50 years in order to better constrain the structure and geometry of the transitional field. In addition, over the past two decades, numerical dynamo simulations have also provided insights into the reversal mechanism. Yet despite the large paleomagnetic database, controversial interpretations of records of the transitional field persist; they result from two characteristics inherent to all reversals, both of which are detrimental to an ambiguous analysis. On the one hand, the reversal process is rapid and requires adequate temporal resolution. On the other hand, weak field intensities during a reversal can affect the fidelity of magnetic recording in sedimentary records. This paper is aimed at reviewing critically the main reversal features derived from paleomagnetic records and at analyzing some of these features in light of numerical simulations. We discuss in detail the fidelity of the signal extracted from paleomagnetic records and pay special attention to their resolution with respect to the timing and mechanisms involved in the magnetization process. Records from marine sediments dominate the database. They give rise to transitional field models that often lead to overinterpret the data. Consequently, we attempt to separate robust results (and their subsequent interpretations) from those that do not stand on a strong observational footing. Finally, we discuss new avenues that should favor progress to better characterize and understand transitional field behavior.",
    url = "https://doi.org/10.1002/2015rg000506",
    doi = "10.1002/2015rg000506",
    openalex = "W2309700037",
    references = "doi101007s1121401096596"
}

Procedures introduced here make it possible, first, to show that background (piecemeal) extinction is recorded throughout geologic stages and substages (not all extinction has occurred suddenly at the ends of such intervals); second, to separate out background extinction from mass extinction for a major crisis in earth history; and third, to correct for clustering of extinctions when using the rarefaction method to estimate the percentage of species lost in a mass extinction. Also presented here is a method for estimating the magnitude of the Signor-Lipps effect, which is the incorrect assignment of extinctions that occurred during a crisis to an interval preceding the crisis because of the incompleteness of the fossil record. Estimates for the magnitudes of mass extinctions presented here are in most cases lower than those previously published. They indicate that only ∼81% of marine species died out in the great terminal Permian crisis, whereas levels of 90-96% have frequently been quoted in the literature. Calculations of the latter numbers were incorrectly based on combined data for the Middle and Late Permian mass extinctions. About 90 orders and more than 220 families of marine animals survived the terminal Permian crisis, and they embodied an enormous amount of morphological, physiological, and ecological diversity. Life did not nearly disappear at the end of the Permian, as has often been claimed.

@article{doi101073pnas1613094113,
    author = "Stanley, Steven M.",
    title = "Estimates of the magnitudes of major marine mass extinctions in earth history",
    year = "2016",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Procedures introduced here make it possible, first, to show that background (piecemeal) extinction is recorded throughout geologic stages and substages (not all extinction has occurred suddenly at the ends of such intervals); second, to separate out background extinction from mass extinction for a major crisis in earth history; and third, to correct for clustering of extinctions when using the rarefaction method to estimate the percentage of species lost in a mass extinction. Also presented here is a method for estimating the magnitude of the Signor-Lipps effect, which is the incorrect assignment of extinctions that occurred during a crisis to an interval preceding the crisis because of the incompleteness of the fossil record. Estimates for the magnitudes of mass extinctions presented here are in most cases lower than those previously published. They indicate that only ∼81\% of marine species died out in the great terminal Permian crisis, whereas levels of 90-96\% have frequently been quoted in the literature. Calculations of the latter numbers were incorrectly based on combined data for the Middle and Late Permian mass extinctions. About 90 orders and more than 220 families of marine animals survived the terminal Permian crisis, and they embodied an enormous amount of morphological, physiological, and ecological diversity. Life did not nearly disappear at the end of the Permian, as has often been claimed.",
    url = "https://doi.org/10.1073/pnas.1613094113",
    doi = "10.1073/pnas.1613094113",
    openalex = "W2529501031",
    references = "doi101002gj1090, doi101007978364270831215, doi101016s001282520000026x, doi101016s0012825203000825, doi101017s0094837300013178, doi101130g211551, doi101146annurevearth33092203122654, doi1016660094837320050310006poaeit20co2, doi105860choice435903"
}

Abstract The record of reversals of the geomagnetic field has played an integral role in the development of plate tectonic theory. Statistical analyses of the reversal record are aimed at detailing patterns and linking those patterns to core–mantle processes. The geomagnetic polarity timescale is a dynamic record and new paleomagnetic and geochronologic data provide additional detail. In this paper, we examine the periodicity revealed in the reversal record back to 375 million years ago (Ma) using Fourier analysis. Four significant peaks were found in the reversal power spectra within the 16–40-million-year range (Myr). Plotting the function constructed from the sum of the frequencies of the proximal peaks yield a transient 26 Myr periodicity, suggesting chaotic motion with a periodic attractor. The possible 16 Myr periodicity, a previously recognized result, may be correlated with ‘pulsation’ of mantle plumes and perhaps; more tentatively, with core–mantle dynamics originating near the large low shear velocity layers in the Pacific and Africa. Planetary magnetic fields shield against charged particles, which can give rise to radiation at the surface and ionize the atmosphere, which is a loss mechanism particularly relevant to M stars. Understanding the origin and development of planetary magnetic fields can shed light on the habitable zone.

@article{doi101017s1473550417000040,
    author = "Melott, Adrian L. and Pivarunas, Anthony F. and Meert, Joseph G. and Lieberman, Bruce S.",
    title = "Does the planetary dynamo go cycling on? Re-examining the evidence for cycles in magnetic reversal rate",
    year = "2017",
    journal = "International Journal of Astrobiology",
    abstract = "Abstract The record of reversals of the geomagnetic field has played an integral role in the development of plate tectonic theory. Statistical analyses of the reversal record are aimed at detailing patterns and linking those patterns to core–mantle processes. The geomagnetic polarity timescale is a dynamic record and new paleomagnetic and geochronologic data provide additional detail. In this paper, we examine the periodicity revealed in the reversal record back to 375 million years ago (Ma) using Fourier analysis. Four significant peaks were found in the reversal power spectra within the 16–40-million-year range (Myr). Plotting the function constructed from the sum of the frequencies of the proximal peaks yield a transient 26 Myr periodicity, suggesting chaotic motion with a periodic attractor. The possible 16 Myr periodicity, a previously recognized result, may be correlated with ‘pulsation’ of mantle plumes and perhaps; more tentatively, with core–mantle dynamics originating near the large low shear velocity layers in the Pacific and Africa. Planetary magnetic fields shield against charged particles, which can give rise to radiation at the surface and ionize the atmosphere, which is a loss mechanism particularly relevant to M stars. Understanding the origin and development of planetary magnetic fields can shed light on the habitable zone.",
    url = "https://doi.org/10.1017/s1473550417000040",
    doi = "10.1017/s1473550417000040",
    openalex = "W2509823199",
    references = "black1967cosmic, crossref1985magnetic, doi1010020471722235, doi101090s00255718196501785861, doi101109tsmc19774309709, doi101126science21545391501, doi1011300091761319910190963gcos23co2, doi1023071268794, doi1023072003354, doi1023072008673, doi1023072669794, doi105860choice263285"
}

In a recent Rapid Communication in this journal, Erlykin et al. (2017) examined the evidence for periodicities in extinction rate in a Bambach compilation of the Sepkoski archive on the ranges of marine genera through time. They claimed that they found insignificant evidence for any periodicities in extinction through time, which they say argues against the possibility of astronomical causation of extinctions. We have found a number of problems with this conclusion. We demonstrate that mixing the extinction dynamics of the unique marine fauna from 465 to 530 Ma (that are also inadequately dated) with the extinction data with recently revised dates from 0 to 465 Ma obscures a significant periodicity in extinction that characterizes the last 465 myr. We also contend that their rejection of possible astronomical causes of extinction is based on a logical fallacy. We do not deal in this paper with the work of Erlykin et al. (2017) on cratering, which is a topic they address specifically, nor do we consider various possible causes of pulses of extinction. We are concerned with their spectral analysis of extinction, and their argument that their results rule out astronomical causes of extinction. This is logically false because if A implies B, it does not follow that not-A implies not-B. Even if periodicities related to extinction were not significant there are numerous astronomical phenomena unrelated to periodic orbital timing that could potentially be involved in extinction events. Also, even if the one astronomical pattern Erlykin et al. (2017) consider is too irregular to be detected by Fourier analysis of data, there are other periodic astronomical processes that could be. Erlykin et al. (2017) analysed data on proportions of extinction in substages with dates from the 2012 Geologic Time Scale provided by one of us. The data were originally compiled for Bambach (2006, supp. material) and updated with revised dates after publication of Gradstein et al. (2012) (data used in Melott & Bambach 2014; Erlykin et al. 2017). Erlykin et al. (2017) discussed what methods to use in analysing these data for periodicities, and cite the work of Omerbashich (2006). Although their point that errors can be introduced in manipulating data is well-taken, the cited work is flawed. Omerbashich's type of spectral analysis was claimed to give different results from Fourier Transform methods, but in fact it has been shown that failure to detrend was the cause of his oddly different results (Cornette 2007; Melott & Bambach 2011). Fourier analysis typically produces a power spectrum (for a discussion see Melott & Bambach 2011) which is usually plotted logarithmically. Erlykin et al. (2017) linearly plotted amplitudes against period (not frequency). We here re-examine the extinction analysis shown in their figure 3. We restrict our attention to the extinction analysis (their fig. 3A–C) and its implications, and do not deal with cratering analysis (their fig. 3D). Each component of their figure 3 either included data that we feel are inappropriate because of their unique biological source and imprecise current dating, or left out valuable data. In the examination of shortened time periods (their fig. 3B–C) they left out the two major Permian events from both, two of the four largest extinction proportions in the last 465 myr. Secondly, in figure 3A, which did include the end-Permian event, they included data back to 530 Ma. As will be discussed at length below, it is self-defeating to link extinction data from 465 to 530 Ma with the extinction data from 0 to 465 Ma because the nearly complete difference biologically of the fauna in the Cambrian from that of later time, the unreliable dating of the available data for the earlier interval, and the close temporal spacing of very high extinction values within the Cambrian preclude getting useful information from patterns expressed by data from the more recent span of time. Data prior to 475 Ma were excluded in Melott & Bambach (2014) for these reasons. Thus figure 3A in Erlykin et al. (2017) should not be treated as equivalent to a replication of our work. We will first show our equivalent analysis to figure 3A of Erlykin et al. (2017), as our Figure 1A. We use the standard time series analysis software AutoSignal v. 1.7 (http://www.sigmaplot.co.uk/products/autosignal/autosignal.php) as in our previous publications. Our test case for equivalence is the Sepkoski–Bambach data, fractional extinction rates back to 530 Ma. In Figure 1A we show the result of Lomb–Scargle analysis, closely similar to that described under ‘Fourier analysis’ in Erlykin et al. (2017). Our results are also nearly identical to those seen in Erlykin et al. (2017, fig. 3A). Attention should be directed to the small peak near 27 myr that is not much bigger than the other peaks. It is more usual in time series study to plot power spectra. In Figure 1B we show the power spectra equivalent to the results in Figure 1A; in fact, one is computed from the other. The power is proportional to the square of the amplitude, and it is normally plotted against the frequency, which is the inverse of the period. In Figure 1C the power spectrum is shown again, this time computed by linear interpolation to 1 myr spacing and Fourier transform, again using AutoSignal 1.7. In this case significance levels assigned by AutoSignal are shown for 50%, 90%, 95%, 99%, and 99.9%, using Monte Carlos based on spectra with similar measured attributes. In agreement with the results reported by Erlykin et al. (2017), none of the peaks approach significance. Melott & Bambach (2014) stated that one should assign extinctions to the ends of intervals (see Foote 2005) and that it is best to exclude data before 470 Ma for the reasons mentioned briefly above and discussed more fully later in this paper. In Figure 2A we show the analysis for the data covering the last 465 myr and omitting the data from 466 to 530 Ma, but otherwise using the same approach as in Figure 1. The result is quite different: the peak at about 27 myr rises to the 95% confidence level. Although there is also a peak of a similar confidence level at a frequency of 0.0715, corresponding to a period of 14 myr, which may or may not be important, caution should be exercised when a feature is found which is not too much greater than the interval length. It is simply not well enough sampled to make strong conclusions. At any rate, we will not consider this peak further here. However, it possibly may be relevant that this peak is not too different from a spectral feature found in the power spectrum of magnetic reversal rate for the Earth (Melott et al. 2017a). However, a possible connection be by the that through the and those be by the this for At this it is to the of our of 465 Ma on the significance level. 1 the significance level for the 27 myr extinction period in the data various The of Cambrian data, or the of the end-Permian the a of at In we have shown that the of significant periodicity by Erlykin et al. (2017) is based on the of extinction proportions and dates from 465 to 530 Ma. they left this data period as in their figure they also examined time periods and left out the two major Permian to the we the same data used by Erlykin et al. (2017) for intervals from 0 to 465 Ma, we 95% confidence in the of a periodicity of 27 myr in of extinction. We that this is equivalent to the result of & Sepkoski detected a myr periodicity for the myr. Our period because of the of the for the and they The revised and dates for numerous intervals in the that periodicity back the that it is a even if current data do not of it earlier is difference in from Erlykin et al. (2017). They stated that they were for peaks above a is to the peaks above the in a of the They the of any peak to level or it rises above level. However, the significance of a spectral peak much it rises above its & Our in AutoSignal was as Each proportional extinction rate is with the 2012 Geologic Time Scale data for the of its This data is linearly data to a 1 myr sampled data for Fourier the of this to Lomb–Scargle for this data see also Melott & Bambach The data is for by data from 465 Ma and The data is by a to a and it is because we are in about any that may data do not the use of any more Figure the values at very and high which not be to a length of 465 myr and a interval of about in our paper and Erlykin et al. (2017) have included the of It also has for significance levels by for that there is a peak at the left that be claimed as significant if we were amplitudes described in the in Erlykin et it is of the frequency which has a that it is a significant This is a very in and other time series spectra. if can be found in of & is a of the significance of the peak at about as a on the results from We can as the we that it is about power than the of values The significance can be as 1 is the number of data back to 465 and is This of which is not too the by the This difference in peaks to their than to the is to be a of the difference in our to Erlykin et al. (2017). Erlykin et al. (2017) to the of extinction for substages back to 530 Ma with a linear used for the data as shown in their figure 1. are reasons using the available data from prior to about 465 Ma is not for analysing extinction patterns through the fauna in the Cambrian was and that it may have to than later the spacing data in time and Ma, with the high extinction proportions that interval, any in of the available data is not The Cambrian fauna was and different to later in the As is well Cambrian of the described genera in the by one of is unique to the The the Cambrian also in in even within the & Bambach that in through the of these were to the Cambrian and a its by the of the Cambrian and in from the by the one of the a significant component in the Cambrian & Bambach and of the of the Cambrian was before any of the that make the fauna to Cambrian were than those of later time. Bambach et al. the of from Cambrian levels in the number of of This and the fact that in major type that use in was more than in Cambrian This has been in as well & in is by to of or at to which could rates of (see The high rate of of the Cambrian the and as the et al. Although we do not have a of these in and in may have extinction a major in extinction dynamics did the of the Cambrian and the The extinction proportions from near to for the of the even as more than a of & Bambach The in extinction pattern is by the in extinction the et al. fig. It is even possible that the Cambrian fauna a different of to and extinctions because of its or its or its none of which have the marine fauna the Cambrian much from later time it is to that the Cambrian fauna should not be included with the of the of the in analysis of extinction. equivalent to the extinction on other in the events are not as events because was very than of the temporal spacing of the intervals of high extinction was about as as a the last 465 myr A periodic in extinction data than a be if data from the Cambrian are with that for the of the because of the of high extinction values in the Cambrian the of the in the The data used in the discussed here were originally compiled by the Sepkoski (data to Bambach by Sepkoski and after as Sepkoski Sepkoski used a of intervals that are by the for the Cambrian in Sepkoski with those in Gradstein et al. The temporal of the Sepkoski data is not a but for the interval are not because agreement on those in the has not been In fact, to the data it may be to back to the and assign and extinction to its because of the Sepkoski used may be two of the of the dates for the of can be but they are The dates be at this time. using the Cambrian data in a periodicity analysis is not analysis of the first above could be of the of the periodicity and 0 Ma if that fauna from later as is possible for and reasons. The and discussed above are to the pattern of periodicity to The in the two earlier of this paper demonstrate that data from Ma with the data from Ma obscures the periodicity in the Ma data. data from Ma should be from analysis of periodicity of extinction. be we analysis of periodicity at 465 Ma because the high values the to extinction that at Ma may Cambrian and not to that of later is a logical in the by the of Erlykin et al. (2017) astronomical causes of extinction. As a in their they show that periodicity of the of the about the is too to a peak in a Fourier the of astronomical phenomena to extinctions is not well et al. the use of the be as their point to the by the is that astronomical processes are to to extinction events. They may have periodic Erlykin et al. (2017) did not their to that (see This is also by a in their causes for can be In this case the was used because they do the as involved with the (see in the as as the by these of Erlykin et al. (2017) is we point out that it is a logical to that if A implies B, not-A implies not-B. because one astronomical too much for its periodicity to in a Fourier analysis does not periodic astronomical phenomena could be enough to be analysed by Fourier because one periodic astronomical be in a Fourier analysis does not to the astronomical phenomena to extinctions is not well et al. At the point Erlykin et al. (2017) that in the period of of the through the as it the make of the period of the by Fourier analysis et al. and fig. they that significance of peaks in extinction is to the for astronomical and their discussion by this we that there is evidence that have from the et al. et al. with other about in periodicities that in astronomical phenomena as a cause for extinctions has been by of periodicity extinction and of periodicity astronomical causes are In fact, there are astronomical phenomena which are for extinctions or and are not to be as possibly et al. for the event, but for that event, as well as events as and (Melott & Melott Melott et al. Even if there to be periodicity of extinction, that not preclude astronomical phenomena as causes of a of extinction events Erlykin et al. for the The earlier of the two in the above significance of peaks in extinction is to the for astronomical this of logical because one astronomical periodicity of the of the through the may be that it not periodic extinctions as as the data on extinctions that at the last 465 myr does not that periodicity in extinctions is to for astronomical processes that are causes of extinction. It does not preclude astronomical processes from a more 27 myr periodicity than may in the of the through the one further after their the in the of the through the at Erlykin et al. (2017, claimed that astronomical cause be to have a in period and than astronomical processes that be causes of extinction are not orbital The Fourier discussed above use data on extinction from intervals 465 Ma and the in the of demonstrate that there is a myr periodicity in the data. This periodicity can be expressed as a recent is at Ma. This can be as a and in the will myr back through time. The included in the analysis is at Ma. there will be through in the myr periodicity as a The last was and the in the analysis used here was Ma. can the further back in time as discussed the data for the Cambrian is for periodicity analysis for reasons. in extinction that are more near a and near a in greater and of extinction in this is the case one more extinction events to be with the than the a test be of the Fourier analysis reported above if can a of extinction events be levels of extinction are quite in the four intervals et al. and are of more extinction events than are at in the is one can a different The to a on the of implies that there are pulses of extinction near the ends of Foote extinction data and that a of extinction interval was by the available data. there also be extinction, the used for in the and analysis the of extinction data at the ends of the as this may be for analysing extinction data through time, the of what intervals have of extinction the events In to which intervals can be to have more extinction than those in their Bambach four different methods of extinction data from the Sepkoski The four methods a spectrum from to The used the data and well of ranges to the of substages included in the intervals the well The did not reported from one interval and that the to be used ends of their ranges at the level. the other two methods, one was more than the first in data and the other interval but for Bambach to interval as a extinction if and if the interval a peak of of extinction and a peak of rate of extinction in four of the data. extinction is at or near the of interval 2005) rate of extinction for the length of the is not for the rate at which extinction in a the end-Permian extinction than but the is myr in length. the rate of extinction in the end-Permian have been about greater than one for the The rate was used at was that intervals (for which is to be because of the time for extinctions to not be for a small peak of but could if they extinction to make a peak in rate the time In the of data, Melott & Bambach (2014) used the 2012 Geologic Time Scale et al. to of in dating, intervals that peaks in methods of but for which the that extinction was not to a interval within the that a was of extinction than using the which has the of a even for these intervals there is to be a of extinction in the interval of Foote and the of at of in the are the best of the timing of these events. are of these intervals of extinction in the Ma time span after the in extinction dynamics and more in the earlier Ma time in the of the these intervals are a peak of of extinction and rate of extinction in four of extinction data from they are of extinction the data are are the intervals we to in the of the 27 myr Figure 3 the of the of the time of for the intervals of extinction as they to the myr periodicity Figure 3 was by the length of time before or after a myr periodicity for the of of the intervals As the extinction, at Ma myr prior to the myr periodicity and the end-Permian extinction event, at after the myr periodicity the is plotted at myr before the is at and the end-Permian is plotted at because it myr after the in the It may to give values for dates and values for dates but if about the of the of time to back in time from the periodicity for the events that were earlier and more time to to the events that after Figure 3 a very of intervals of extinction of the intervals in a a myr span within the the of which is from the point in the periodicity by myr. The intervals are this This can be of as a of than myr a time of myr. The fact that the periodicity is expressed by the data shown in our and not by these major that the periodicity is a in in the of not the and of cause of extinction events. the periodicity in extinction a and of for a time is not time in could that more and more to The events that on extinction events be more to have major the the were in the of for bigger events than on the of the is it that of events in myr of the myr of the The can be used to of of events. The is that there is the intervals of extinction and the myr This is of the of this in this case at the intervals of extinction there is the peaks should be at with to this The if the events are not related to the is the fractional time of the interval, or The is a standard in for the of events a Although one may not the timing as very close to the of the we can one as the of time, and the as with the for the of or more of data within myr of the of the of the myr periodicity is the periodicity is the of major extinction events the of the periodic be to show major events. of the intervals of extinction in a myr span in the myr periodicity more than a of the and the point the events were with time interval the of is This is with a from the of the myr periodicity to the same as the in the timing of the of intervals of extinction after the in the can be in Figure 3. The high significance of the of data and in the data is evidence that the 27 myr periodicity in extinction is a this of the intervals of extinction in the the In the period Ma, out of intervals within the which has a of if they were at the of the are and in to the length of the periodicity the results in of the we the of as related to the periodicity also about the of the timing of the intervals of extinction to the of data we assigned the dates to of the myr from the point of 0 by the same as the of the of intervals of extinction the of myr. The Ma data included interval They are nearly through the periodicity in the of the myr periodicity on the point in the intervals of extinction seen in in the to the are in the that the and are in the to the data include the intervals of extinction the intervals of extinction in the on the point of the is that but included in the of the period as the discussed above and in in the to the to the of the in none in the the and in the to the 3 to the left of the in 3 the of the which is the the and of the of the The above that the of the intervals of extinction is related to the 27 myr of extinction were with not to analysis of periodicity in any and which also as extinction the data on the interval is in 27 myr but do have a significant to the 27 myr The of the Cambrian and was that intervals very high levels of extinction. of the Cambrian intervals that as interval of extinction does within the of spacing values in the for Ma, but two of the Cambrian intervals of extinction in the myr from either the point or the spacing that for none of the intervals of extinction This last point is further that to extinction in the of the was simply not to that seen and analysis of periodicity for that of the The 27 myr periodicity in extinction is and However, the of and high extinction, and getting dates for data prior to 465 Ma are that data from the fauna in the Cambrian simply be with those for later to periodicity of extinction through time. Erlykin et al. (2017) to the data which we have shown obscures the of the 27 myr periodicity seen when the data from 0 to 465 Ma. In the discussion of Erlykin et al. implies that they did not the of the power spectrum when peak which their conclusions. problems in the discussion by Erlykin et al. (2017), of periodicity of extinction and its to astronomical that in the of the through the is to astronomical processes as a cause of periodic extinction is not The that it does not one or the high extinction values and Ma and 470 and 530 Ma from because the of these high extinction values is is not the values from to Ma obscures the of the 27 myr periodicity in extinction when the of the the Ma data data that obscures the significance of the 27 myr periodicity in extinction that characterizes the last 465 myr and but be This discussion of Erlykin et al. (2017) has been to the in that paper that the results in other about extinction patterns time. are a number of other with Erlykin et al. (2017) but they are of the major discussed and in the of and we not the point Erlykin et al. (2017) did not the fact that the data on extinctions are not They a major of the of and are related not to the ends of ranges in time, but also to the and dynamics of the at those and the various and that can on the We our is and periodic and astronomical causes of extinction may we that are the be that and the that the and that these problems is that by Our results are at with the & 2011) in which periodic in this case at a 27 myr a on which a of events from a of causes are to major extinction events by the We do not the cause of the 27 myr periodicity in extinction, but data covering of the last that it does It may be astronomical or & Sepkoski to have been with the current time that periodicity can be at back to 465 Ma. to that study is because of dynamics and the of a is for from We our for the of the point of the periodicity analysis to our attention as of as well as in other did of data, the first of the the and and the the first attention to and with the

@article{doi101111pala12322,
    author = "Melott, Adrian L. and Bambach, Richard K.",
    title = "Comments on: Periodicity in the extinction rate and possible astronomical causes – comment on mass extinctions over the last 500 myr: an astronomical cause? (Erlykin et al.)",
    year = "2017",
    journal = "Palaeontology",
    abstract = "In a recent Rapid Communication in this journal, Erlykin et al. (2017) examined the evidence for periodicities in extinction rate in a Bambach compilation of the Sepkoski archive on the ranges of marine genera through time. They claimed that they found insignificant evidence for any periodicities in extinction through time, which they say argues against the possibility of astronomical causation of extinctions. We have found a number of problems with this conclusion. We demonstrate that mixing the extinction dynamics of the unique marine fauna from 465 to 530 Ma (that are also inadequately dated) with the extinction data with recently revised dates from 0 to 465 Ma obscures a significant periodicity in extinction that characterizes the last 465 myr. We also contend that their rejection of possible astronomical causes of extinction is based on a logical fallacy. We do not deal in this paper with the work of Erlykin et al. (2017) on cratering, which is a topic they address specifically, nor do we consider various possible causes of pulses of extinction. We are concerned with their spectral analysis of extinction, and their argument that their results rule out astronomical causes of extinction. This is logically false because if A implies B, it does not follow that not-A implies not-B. Even if periodicities related to extinction were not significant there are numerous astronomical phenomena unrelated to periodic orbital timing that could potentially be involved in extinction events. Also, even if the one astronomical pattern Erlykin et al. (2017) consider is too irregular to be detected by Fourier analysis of data, there are other periodic astronomical processes that could be. Erlykin et al. (2017) analysed data on proportions of extinction in substages with dates from the 2012 Geologic Time Scale provided by one of us. The data were originally compiled for Bambach (2006, supp. material) and updated with revised dates after publication of Gradstein et al. (2012) (data used in Melott \& Bambach 2014; Erlykin et al. 2017). Erlykin et al. (2017) discussed what methods to use in analysing these data for periodicities, and cite the work of Omerbashich (2006). Although their point that errors can be introduced in manipulating data is well-taken, the cited work is flawed. Omerbashich's type of spectral analysis was claimed to give different results from Fourier Transform methods, but in fact it has been shown that failure to detrend was the cause of his oddly different results (Cornette 2007; Melott \& Bambach 2011). Fourier analysis typically produces a power spectrum (for a discussion see Melott \& Bambach 2011) which is usually plotted logarithmically. Erlykin et al. (2017) linearly plotted amplitudes against period (not frequency). We here re-examine the extinction analysis shown in their figure 3. We restrict our attention to the extinction analysis (their fig. 3A–C) and its implications, and do not deal with cratering analysis (their fig. 3D). Each component of their figure 3 either included data that we feel are inappropriate because of their unique biological source and imprecise current dating, or left out valuable data. In the examination of shortened time periods (their fig. 3B–C) they left out the two major Permian events from both, two of the four largest extinction proportions in the last 465 myr. Secondly, in figure 3A, which did include the end-Permian event, they included data back to 530 Ma. As will be discussed at length below, it is self-defeating to link extinction data from 465 to 530 Ma with the extinction data from 0 to 465 Ma because the nearly complete difference biologically of the fauna in the Cambrian from that of later time, the unreliable dating of the available data for the earlier interval, and the close temporal spacing of very high extinction values within the Cambrian preclude getting useful information from patterns expressed by data from the more recent span of time. Data prior to 475 Ma were excluded in Melott \& Bambach (2014) for these reasons. Thus figure 3A in Erlykin et al. (2017) should not be treated as equivalent to a replication of our work. We will first show our equivalent analysis to figure 3A of Erlykin et al. (2017), as our Figure 1A. We use the standard time series analysis software AutoSignal v. 1.7 (http://www.sigmaplot.co.uk/products/autosignal/autosignal.php) as in our previous publications. Our test case for equivalence is the Sepkoski–Bambach data, fractional extinction rates back to 530 Ma. In Figure 1A we show the result of Lomb–Scargle analysis, closely similar to that described under ‘Fourier analysis’ in Erlykin et al. (2017). Our results are also nearly identical to those seen in Erlykin et al. (2017, fig. 3A). Attention should be directed to the small peak near 27 myr that is not much bigger than the other peaks. It is more usual in time series study to plot power spectra. In Figure 1B we show the power spectra equivalent to the results in Figure 1A; in fact, one is computed from the other. The power is proportional to the square of the amplitude, and it is normally plotted against the frequency, which is the inverse of the period. In Figure 1C the power spectrum is shown again, this time computed by linear interpolation to 1 myr spacing and Fourier transform, again using AutoSignal 1.7. In this case significance levels assigned by AutoSignal are shown for 50\%, 90\%, 95\%, 99\%, and 99.9\%, using Monte Carlos based on spectra with similar measured attributes. In agreement with the results reported by Erlykin et al. (2017), none of the peaks approach significance. Melott \& Bambach (2014) stated that one should assign extinctions to the ends of intervals (see Foote 2005) and that it is best to exclude data before 470 Ma for the reasons mentioned briefly above and discussed more fully later in this paper. In Figure 2A we show the analysis for the data covering the last 465 myr and omitting the data from 466 to 530 Ma, but otherwise using the same approach as in Figure 1. The result is quite different: the peak at about 27 myr rises to the 95\% confidence level. Although there is also a peak of a similar confidence level at a frequency of 0.0715, corresponding to a period of 14 myr, which may or may not be important, caution should be exercised when a feature is found which is not too much greater than the interval length. It is simply not well enough sampled to make strong conclusions. At any rate, we will not consider this peak further here. However, it possibly may be relevant that this peak is not too different from a spectral feature found in the power spectrum of magnetic reversal rate for the Earth (Melott et al. 2017a). However, a possible connection be by the that through the and those be by the this for At this it is to the of our of 465 Ma on the significance level. 1 the significance level for the 27 myr extinction period in the data various The of Cambrian data, or the of the end-Permian the a of at In we have shown that the of significant periodicity by Erlykin et al. (2017) is based on the of extinction proportions and dates from 465 to 530 Ma. they left this data period as in their figure they also examined time periods and left out the two major Permian to the we the same data used by Erlykin et al. (2017) for intervals from 0 to 465 Ma, we 95\% confidence in the of a periodicity of 27 myr in of extinction. We that this is equivalent to the result of \& Sepkoski detected a myr periodicity for the myr. Our period because of the of the for the and they The revised and dates for numerous intervals in the that periodicity back the that it is a even if current data do not of it earlier is difference in from Erlykin et al. (2017). They stated that they were for peaks above a is to the peaks above the in a of the They the of any peak to level or it rises above level. However, the significance of a spectral peak much it rises above its \& Our in AutoSignal was as Each proportional extinction rate is with the 2012 Geologic Time Scale data for the of its This data is linearly data to a 1 myr sampled data for Fourier the of this to Lomb–Scargle for this data see also Melott \& Bambach The data is for by data from 465 Ma and The data is by a to a and it is because we are in about any that may data do not the use of any more Figure the values at very and high which not be to a length of 465 myr and a interval of about in our paper and Erlykin et al. (2017) have included the of It also has for significance levels by for that there is a peak at the left that be claimed as significant if we were amplitudes described in the in Erlykin et it is of the frequency which has a that it is a significant This is a very in and other time series spectra. if can be found in of \& is a of the significance of the peak at about as a on the results from We can as the we that it is about power than the of values The significance can be as 1 is the number of data back to 465 and is This of which is not too the by the This difference in peaks to their than to the is to be a of the difference in our to Erlykin et al. (2017). Erlykin et al. (2017) to the of extinction for substages back to 530 Ma with a linear used for the data as shown in their figure 1. are reasons using the available data from prior to about 465 Ma is not for analysing extinction patterns through the fauna in the Cambrian was and that it may have to than later the spacing data in time and Ma, with the high extinction proportions that interval, any in of the available data is not The Cambrian fauna was and different to later in the As is well Cambrian of the described genera in the by one of is unique to the The the Cambrian also in in even within the \& Bambach that in through the of these were to the Cambrian and a its by the of the Cambrian and in from the by the one of the a significant component in the Cambrian \& Bambach and of the of the Cambrian was before any of the that make the fauna to Cambrian were than those of later time. Bambach et al. the of from Cambrian levels in the number of of This and the fact that in major type that use in was more than in Cambrian This has been in as well \& in is by to of or at to which could rates of (see The high rate of of the Cambrian the and as the et al. Although we do not have a of these in and in may have extinction a major in extinction dynamics did the of the Cambrian and the The extinction proportions from near to for the of the even as more than a of \& Bambach The in extinction pattern is by the in extinction the et al. fig. It is even possible that the Cambrian fauna a different of to and extinctions because of its or its or its none of which have the marine fauna the Cambrian much from later time it is to that the Cambrian fauna should not be included with the of the of the in analysis of extinction. equivalent to the extinction on other in the events are not as events because was very than of the temporal spacing of the intervals of high extinction was about as as a the last 465 myr A periodic in extinction data than a be if data from the Cambrian are with that for the of the because of the of high extinction values in the Cambrian the of the in the The data used in the discussed here were originally compiled by the Sepkoski (data to Bambach by Sepkoski and after as Sepkoski Sepkoski used a of intervals that are by the for the Cambrian in Sepkoski with those in Gradstein et al. The temporal of the Sepkoski data is not a but for the interval are not because agreement on those in the has not been In fact, to the data it may be to back to the and assign and extinction to its because of the Sepkoski used may be two of the of the dates for the of can be but they are The dates be at this time. using the Cambrian data in a periodicity analysis is not analysis of the first above could be of the of the periodicity and 0 Ma if that fauna from later as is possible for and reasons. The and discussed above are to the pattern of periodicity to The in the two earlier of this paper demonstrate that data from Ma with the data from Ma obscures the periodicity in the Ma data. data from Ma should be from analysis of periodicity of extinction. be we analysis of periodicity at 465 Ma because the high values the to extinction that at Ma may Cambrian and not to that of later is a logical in the by the of Erlykin et al. (2017) astronomical causes of extinction. As a in their they show that periodicity of the of the about the is too to a peak in a Fourier the of astronomical phenomena to extinctions is not well et al. the use of the be as their point to the by the is that astronomical processes are to to extinction events. They may have periodic Erlykin et al. (2017) did not their to that (see This is also by a in their causes for can be In this case the was used because they do the as involved with the (see in the as as the by these of Erlykin et al. (2017) is we point out that it is a logical to that if A implies B, not-A implies not-B. because one astronomical too much for its periodicity to in a Fourier analysis does not periodic astronomical phenomena could be enough to be analysed by Fourier because one periodic astronomical be in a Fourier analysis does not to the astronomical phenomena to extinctions is not well et al. At the point Erlykin et al. (2017) that in the period of of the through the as it the make of the period of the by Fourier analysis et al. and fig. they that significance of peaks in extinction is to the for astronomical and their discussion by this we that there is evidence that have from the et al. et al. with other about in periodicities that in astronomical phenomena as a cause for extinctions has been by of periodicity extinction and of periodicity astronomical causes are In fact, there are astronomical phenomena which are for extinctions or and are not to be as possibly et al. for the event, but for that event, as well as events as and (Melott \& Melott Melott et al. Even if there to be periodicity of extinction, that not preclude astronomical phenomena as causes of a of extinction events Erlykin et al. for the The earlier of the two in the above significance of peaks in extinction is to the for astronomical this of logical because one astronomical periodicity of the of the through the may be that it not periodic extinctions as as the data on extinctions that at the last 465 myr does not that periodicity in extinctions is to for astronomical processes that are causes of extinction. It does not preclude astronomical processes from a more 27 myr periodicity than may in the of the through the one further after their the in the of the through the at Erlykin et al. (2017, claimed that astronomical cause be to have a in period and than astronomical processes that be causes of extinction are not orbital The Fourier discussed above use data on extinction from intervals 465 Ma and the in the of demonstrate that there is a myr periodicity in the data. This periodicity can be expressed as a recent is at Ma. This can be as a and in the will myr back through time. The included in the analysis is at Ma. there will be through in the myr periodicity as a The last was and the in the analysis used here was Ma. can the further back in time as discussed the data for the Cambrian is for periodicity analysis for reasons. in extinction that are more near a and near a in greater and of extinction in this is the case one more extinction events to be with the than the a test be of the Fourier analysis reported above if can a of extinction events be levels of extinction are quite in the four intervals et al. and are of more extinction events than are at in the is one can a different The to a on the of implies that there are pulses of extinction near the ends of Foote extinction data and that a of extinction interval was by the available data. there also be extinction, the used for in the and analysis the of extinction data at the ends of the as this may be for analysing extinction data through time, the of what intervals have of extinction the events In to which intervals can be to have more extinction than those in their Bambach four different methods of extinction data from the Sepkoski The four methods a spectrum from to The used the data and well of ranges to the of substages included in the intervals the well The did not reported from one interval and that the to be used ends of their ranges at the level. the other two methods, one was more than the first in data and the other interval but for Bambach to interval as a extinction if and if the interval a peak of of extinction and a peak of rate of extinction in four of the data. extinction is at or near the of interval 2005) rate of extinction for the length of the is not for the rate at which extinction in a the end-Permian extinction than but the is myr in length. the rate of extinction in the end-Permian have been about greater than one for the The rate was used at was that intervals (for which is to be because of the time for extinctions to not be for a small peak of but could if they extinction to make a peak in rate the time In the of data, Melott \& Bambach (2014) used the 2012 Geologic Time Scale et al. to of in dating, intervals that peaks in methods of but for which the that extinction was not to a interval within the that a was of extinction than using the which has the of a even for these intervals there is to be a of extinction in the interval of Foote and the of at of in the are the best of the timing of these events. are of these intervals of extinction in the Ma time span after the in extinction dynamics and more in the earlier Ma time in the of the these intervals are a peak of of extinction and rate of extinction in four of extinction data from they are of extinction the data are are the intervals we to in the of the 27 myr Figure 3 the of the of the time of for the intervals of extinction as they to the myr periodicity Figure 3 was by the length of time before or after a myr periodicity for the of of the intervals As the extinction, at Ma myr prior to the myr periodicity and the end-Permian extinction event, at after the myr periodicity the is plotted at myr before the is at and the end-Permian is plotted at because it myr after the in the It may to give values for dates and values for dates but if about the of the of time to back in time from the periodicity for the events that were earlier and more time to to the events that after Figure 3 a very of intervals of extinction of the intervals in a a myr span within the the of which is from the point in the periodicity by myr. The intervals are this This can be of as a of than myr a time of myr. The fact that the periodicity is expressed by the data shown in our and not by these major that the periodicity is a in in the of not the and of cause of extinction events. the periodicity in extinction a and of for a time is not time in could that more and more to The events that on extinction events be more to have major the the were in the of for bigger events than on the of the is it that of events in myr of the myr of the The can be used to of of events. The is that there is the intervals of extinction and the myr This is of the of this in this case at the intervals of extinction there is the peaks should be at with to this The if the events are not related to the is the fractional time of the interval, or The is a standard in for the of events a Although one may not the timing as very close to the of the we can one as the of time, and the as with the for the of or more of data within myr of the of the of the myr periodicity is the periodicity is the of major extinction events the of the periodic be to show major events. of the intervals of extinction in a myr span in the myr periodicity more than a of the and the point the events were with time interval the of is This is with a from the of the myr periodicity to the same as the in the timing of the of intervals of extinction after the in the can be in Figure 3. The high significance of the of data and in the data is evidence that the 27 myr periodicity in extinction is a this of the intervals of extinction in the the In the period Ma, out of intervals within the which has a of if they were at the of the are and in to the length of the periodicity the results in of the we the of as related to the periodicity also about the of the timing of the intervals of extinction to the of data we assigned the dates to of the myr from the point of 0 by the same as the of the of intervals of extinction the of myr. The Ma data included interval They are nearly through the periodicity in the of the myr periodicity on the point in the intervals of extinction seen in in the to the are in the that the and are in the to the data include the intervals of extinction the intervals of extinction in the on the point of the is that but included in the of the period as the discussed above and in in the to the to the of the in none in the the and in the to the 3 to the left of the in 3 the of the which is the the and of the of the The above that the of the intervals of extinction is related to the 27 myr of extinction were with not to analysis of periodicity in any and which also as extinction the data on the interval is in 27 myr but do have a significant to the 27 myr The of the Cambrian and was that intervals very high levels of extinction. of the Cambrian intervals that as interval of extinction does within the of spacing values in the for Ma, but two of the Cambrian intervals of extinction in the myr from either the point or the spacing that for none of the intervals of extinction This last point is further that to extinction in the of the was simply not to that seen and analysis of periodicity for that of the The 27 myr periodicity in extinction is and However, the of and high extinction, and getting dates for data prior to 465 Ma are that data from the fauna in the Cambrian simply be with those for later to periodicity of extinction through time. Erlykin et al. (2017) to the data which we have shown obscures the of the 27 myr periodicity seen when the data from 0 to 465 Ma. In the discussion of Erlykin et al. implies that they did not the of the power spectrum when peak which their conclusions. problems in the discussion by Erlykin et al. (2017), of periodicity of extinction and its to astronomical that in the of the through the is to astronomical processes as a cause of periodic extinction is not The that it does not one or the high extinction values and Ma and 470 and 530 Ma from because the of these high extinction values is is not the values from to Ma obscures the of the 27 myr periodicity in extinction when the of the the Ma data data that obscures the significance of the 27 myr periodicity in extinction that characterizes the last 465 myr and but be This discussion of Erlykin et al. (2017) has been to the in that paper that the results in other about extinction patterns time. are a number of other with Erlykin et al. (2017) but they are of the major discussed and in the of and we not the point Erlykin et al. (2017) did not the fact that the data on extinctions are not They a major of the of and are related not to the ends of ranges in time, but also to the and dynamics of the at those and the various and that can on the We our is and periodic and astronomical causes of extinction may we that are the be that and the that the and that these problems is that by Our results are at with the \& 2011) in which periodic in this case at a 27 myr a on which a of events from a of causes are to major extinction events by the We do not the cause of the 27 myr periodicity in extinction, but data covering of the last that it does It may be astronomical or \& Sepkoski to have been with the current time that periodicity can be at back to 465 Ma. to that study is because of dynamics and the of a is for from We our for the of the point of the periodicity analysis to our attention as of as well as in other did of data, the first of the the and and the the first attention to and with the",
    url = "https://doi.org/10.1111/pala.12322",
    doi = "10.1111/pala.12322",
    openalex = "W2746096951",
    references = "alvarez1980extraterrestrial, doi101017s1473550417000040, doi101073pnas813801, doi101111j14754983200600611x, doi101146annurevearth040809152556, doi101146annurevearth33092203122654, doi1016660094837320040300522oeamdo20co2, doi1016660094837320050310006poaeit20co2, doi101666070341, doi105860choice383341, doi107312webb12678"
}

Abstract It has long been speculated that biological evolution was influenced by ultraviolet radiation (UVR) reaching the Earth's surface, despite imprecise knowledge of the timing of both UVR flux and evolutionary events. The past strength of Earth's dipole field provides a proxy for UVR flux because of its role in maintaining stratospheric ozone. The timing of Quaternary evolutionary events has become better constrained by fossil finds, improved radiometric dating, use of dung fungi as proxies for herbivore populations, and improved ages for nodes in human phylogeny from human mitochondrial DNA and Y chromosomes. The demise of Neanderthals at ~41 ka can now be closely tied to the intensity minimum associated with the Laschamp magnetic excursion, and the survival of anatomically modern humans can be attributed to differences in the aryl hydrocarbon receptor that has a key role in the evolutionary response to UVR flux. Fossil occurrences and dung‐fungal proxies in Australia indicate that episodes of Late Quaternary extinction of mammalian megafauna occurred close to the Laschamp and Blake magnetic excursions. Fossil and dung fungal evidence for the age of the Late Quaternary extinction in North America (and Europe) coincide with a prominent decline in geomagnetic field intensity at ~13 ka. Over the last ~200 kyr, phylogeny based on mitochondrial DNA and Y chromosomes in modern humans yields nodes and bifurcations in evolution corresponding to geomagnetic intensity minima, which supports the proposition that UVR reaching Earth's surface influenced mammalian evolution with the loci of extinction controlled by the geometry of stratospheric ozone depletion.

@article{doi1010292018rg000629,
    author = "Channell, James E T and Vigliotti, Luigi",
    title = "The Role of Geomagnetic Field Intensity in Late Quaternary Evolution of Humans and Large Mammals",
    year = "2019",
    journal = "Reviews of Geophysics",
    abstract = "Abstract It has long been speculated that biological evolution was influenced by ultraviolet radiation (UVR) reaching the Earth's surface, despite imprecise knowledge of the timing of both UVR flux and evolutionary events. The past strength of Earth's dipole field provides a proxy for UVR flux because of its role in maintaining stratospheric ozone. The timing of Quaternary evolutionary events has become better constrained by fossil finds, improved radiometric dating, use of dung fungi as proxies for herbivore populations, and improved ages for nodes in human phylogeny from human mitochondrial DNA and Y chromosomes. The demise of Neanderthals at \textasciitilde 41 ka can now be closely tied to the intensity minimum associated with the Laschamp magnetic excursion, and the survival of anatomically modern humans can be attributed to differences in the aryl hydrocarbon receptor that has a key role in the evolutionary response to UVR flux. Fossil occurrences and dung‐fungal proxies in Australia indicate that episodes of Late Quaternary extinction of mammalian megafauna occurred close to the Laschamp and Blake magnetic excursions. Fossil and dung fungal evidence for the age of the Late Quaternary extinction in North America (and Europe) coincide with a prominent decline in geomagnetic field intensity at \textasciitilde 13 ka. Over the last \textasciitilde 200 kyr, phylogeny based on mitochondrial DNA and Y chromosomes in modern humans yields nodes and bifurcations in evolution corresponding to geomagnetic intensity minima, which supports the proposition that UVR reaching Earth's surface influenced mammalian evolution with the loci of extinction controlled by the geometry of stratospheric ozone depletion.",
    url = "https://doi.org/10.1029/2018rg000629",
    doi = "10.1029/2018rg000629",
    openalex = "W2947719388",
    references = "doi101017s1473550409990073"
}

A striking feature of many natural magnetic fields generated by dynamo action is the occurrence of polarity reversals. Paleomagnetic measurements revealed that the Earth's magnetic field has been characterised by few hundred stochastic polarity switches during its history. The rate of reversals changes in time, maybe obeying some underlying regular pattern. While chaotic dynamical systems can describe the short-term behaviour of the switches of the Earth's magnetic polarity, modelling the long-term variations of the reversal rate is somewhat problematic, as they occur on timescales of tens to hundreds of millions of years, of the order of mantle convection timescales. By investigating data of geomagnetic reversal rates, we find the presence of cycles with variable frequency and show that the transition towards periods where reversals do not occur for tens of million years (superchrons) can be described by a second-order phase transition that we interpret to be driven by variations of the heat flux at the core-mantle boundary (CMB). The model allows us to extract from the reversal sequence quantitative information on the susceptibility of the reversal rate caused by changes in the CMB heat flux amplitude, thus providing direct information on the deep inner layers of the Earth.

@article{doi101038s4159802069916w,
    author = "Carbone, V. and Alberti, Tommaso and Lepreti, Fabio and Vecchio, A.",
    title = "A model for the geomagnetic field reversal rate and constraints on the heat flux variations at the core-mantle boundary",
    year = "2020",
    journal = "Scientific Reports",
    abstract = "A striking feature of many natural magnetic fields generated by dynamo action is the occurrence of polarity reversals. Paleomagnetic measurements revealed that the Earth's magnetic field has been characterised by few hundred stochastic polarity switches during its history. The rate of reversals changes in time, maybe obeying some underlying regular pattern. While chaotic dynamical systems can describe the short-term behaviour of the switches of the Earth's magnetic polarity, modelling the long-term variations of the reversal rate is somewhat problematic, as they occur on timescales of tens to hundreds of millions of years, of the order of mantle convection timescales. By investigating data of geomagnetic reversal rates, we find the presence of cycles with variable frequency and show that the transition towards periods where reversals do not occur for tens of million years (superchrons) can be described by a second-order phase transition that we interpret to be driven by variations of the heat flux at the core-mantle boundary (CMB). The model allows us to extract from the reversal sequence quantitative information on the susceptibility of the reversal rate caused by changes in the CMB heat flux amplitude, thus providing direct information on the deep inner layers of the Earth.",
    url = "https://doi.org/10.1038/s41598-020-69916-w",
    doi = "10.1038/s41598-020-69916-w",
    openalex = "W3047396528",
    references = "doi101017s1473550417000040"
}

Paleontologists define global extinctions on Earth as a loss of about three-quarters of plant and animal species over a relatively short period of time. At least five global extinctions are documented in the Phanerozoic fossil record (~500-million-year period): ~65, 200, 260, 380, and 440 million years ago. In addition, there is evidence of global extinctions in earlier periods of life on Earth - during the Late Cambrian (~500 million years ago) and Ediacaran periods (more than 540 million years ago). There is still no common opinion on the causes of their occurrence. The current study is a systematized review of the data on recorded extinctions of complex life forms on Earth from the moment of their occurrence during the Ediacaran period to the modern period. The review discusses possible causes for mass extinctions in the light of the influence of abiogenic factors, planetary or astronomical, and the consequences of their actions. We evaluate the pros and cons of the hypothesis on the presence of periodicity in the extinction of Phanerozoic marine biota. Strong evidence that allows us to hypothesize that additional mechanisms associated with various internal biotic factors are responsible for the emergence of extinctions in the evolution of complex life forms is discussed. Developing the idea of the internal causes of periodicity and discontinuity in evolution, we propose our own original hypothesis, according to which the bistability phenomenon underlies the complex dynamics of the biota development, which is manifested in the form of global extinctions. The bistability phenomenon arises only in ecosystems with predominant sexual reproduction. Our hypothesis suggests that even in the absence of global abiotic catastrophes, extinctions of biota would occur anyway. However, our hypothesis does not exclude the possibility that in different periods of the Earth's history the biota was subjected to powerful external influences that had a significant impact on its further development, which is reflected in the Earth's fossil record.

@article{doi1018699vj20633,
    author = "Хлебодарова, Т. М. and Лихошвай, В. А.",
    title = "Causes of global extinctions in the history of life: facts and hypotheses",
    year = "2020",
    journal = "Vavilov Journal of Genetics and Breeding",
    abstract = "Paleontologists define global extinctions on Earth as a loss of about three-quarters of plant and animal species over a relatively short period of time. At least five global extinctions are documented in the Phanerozoic fossil record (\textasciitilde 500-million-year period): \textasciitilde 65, 200, 260, 380, and 440 million years ago. In addition, there is evidence of global extinctions in earlier periods of life on Earth - during the Late Cambrian (\textasciitilde 500 million years ago) and Ediacaran periods (more than 540 million years ago). There is still no common opinion on the causes of their occurrence. The current study is a systematized review of the data on recorded extinctions of complex life forms on Earth from the moment of their occurrence during the Ediacaran period to the modern period. The review discusses possible causes for mass extinctions in the light of the influence of abiogenic factors, planetary or astronomical, and the consequences of their actions. We evaluate the pros and cons of the hypothesis on the presence of periodicity in the extinction of Phanerozoic marine biota. Strong evidence that allows us to hypothesize that additional mechanisms associated with various internal biotic factors are responsible for the emergence of extinctions in the evolution of complex life forms is discussed. Developing the idea of the internal causes of periodicity and discontinuity in evolution, we propose our own original hypothesis, according to which the bistability phenomenon underlies the complex dynamics of the biota development, which is manifested in the form of global extinctions. The bistability phenomenon arises only in ecosystems with predominant sexual reproduction. Our hypothesis suggests that even in the absence of global abiotic catastrophes, extinctions of biota would occur anyway. However, our hypothesis does not exclude the possibility that in different periods of the Earth's history the biota was subjected to powerful external influences that had a significant impact on its further development, which is reflected in the Earth's fossil record.",
    url = "https://doi.org/10.18699/vj20.633",
    doi = "10.18699/vj20.633",
    openalex = "W3039864210",
    references = "doi101111pala12322, doi101111pala12334"
}

Earth is one of the inner planets of the Solar System, but - unlike the others - it has an oxidising atmosphere, relatively stable temperature, and a constant geomagnetic field (GMF). The GMF does not only protect life on Earth against the solar wind and cosmic rays, but it also shields the atmosphere itself, thus creating relatively stable environmental conditions. What is more, the GMF could have influenced the origins of life: organisms from archaea to plants and animals may have been using the GMF as a source of spatial information since the very beginning. Although the GMF is constant, it does undergo various changes, some of which, e.g. a reversal of the poles, weaken the field significantly or even lead to its short-term disappearance. This may result in considerable climatic changes and an increased frequency of mutations caused by the solar wind and cosmic radiation. This review analyses data on the influence of the GMF on different aspects of life and it also presents current knowledge in the area. In conclusion, the GMF has a positive impact on living organisms, whereas a diminishing or disappearing GMF negatively affects living organisms. The influence of the GMF may also be an important factor determining both survival of terrestrial organisms outside Earth and the emergence of life on other planets.

@article{doi101007s11084021096125,
    author = "Erdmann, Weronika and Kmita, Hanna and Kosicki, Jakub Z. and Kaczmarek, Łukasz D.",
    title = "How the Geomagnetic Field Influences Life on Earth – An Integrated Approach to Geomagnetobiology",
    year = "2021",
    journal = "Origins of Life and Evolution of Biospheres",
    abstract = "Earth is one of the inner planets of the Solar System, but - unlike the others - it has an oxidising atmosphere, relatively stable temperature, and a constant geomagnetic field (GMF). The GMF does not only protect life on Earth against the solar wind and cosmic rays, but it also shields the atmosphere itself, thus creating relatively stable environmental conditions. What is more, the GMF could have influenced the origins of life: organisms from archaea to plants and animals may have been using the GMF as a source of spatial information since the very beginning. Although the GMF is constant, it does undergo various changes, some of which, e.g. a reversal of the poles, weaken the field significantly or even lead to its short-term disappearance. This may result in considerable climatic changes and an increased frequency of mutations caused by the solar wind and cosmic radiation. This review analyses data on the influence of the GMF on different aspects of life and it also presents current knowledge in the area. In conclusion, the GMF has a positive impact on living organisms, whereas a diminishing or disappearing GMF negatively affects living organisms. The influence of the GMF may also be an important factor determining both survival of terrestrial organisms outside Earth and the emergence of life on other planets.",
    url = "https://doi.org/10.1007/s11084-021-09612-5",
    doi = "10.1007/s11084-021-09612-5",
    openalex = "W3187945566",
    references = "doi101007s1121401096596"
}

@article{doi101016jgr202102018,
    author = "Levashova, Natalia M. and Голованова, И. В. and Rud’ko, D. V. and Данукалов, К. Н. and Rud’ko, S. V. and Sal’manova, R. Yu. and Meert, Joseph G.",
    title = "Late Ediacaran magnetic field hyperactivity: Quantifying the reversal frequency in the Zigan Formation, Southern Urals, Russia",
    year = "2021",
    journal = "Gondwana Research",
    url = "https://doi.org/10.1016/j.gr.2021.02.018",
    doi = "10.1016/j.gr.2021.02.018",
    openalex = "W3136501261",
    references = "doi101007bf00142586, doi101016jcageo201902011, doi101017cbo9780511536045, doi101017s1473550417000040, doi1010292001gc000227, doi101109proc198212433, doi101111j1365246x1980tb02601x, doi101111j1365246x1990tb05683x, doi101111j1365246x201105050x, doi101130b309341, doi10384720418213ab12eb, openalexw2974218786"
}

Abstract Transpolar arcs (TPAs) are believed to predominantly occur under northward interplanetary magnetic field (IMF) conditions with their hemispheric asymmetry controlled by the Sun‐Earth (radial) component of the IMF. In this study, we present observations of TPAs that appear in both the northern and southern hemispheres even during a prolonged interval of radially oriented IMF. The Defense Meteorological Satellite Program (DMSP) F16 and the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellites observed TPAs on the dawnside polar cap in both hemispheres (one TPA structure in the southern hemisphere and two in the northern hemisphere) during an interval of nearly earthward‐oriented IMF on October 29, 2005. The southern hemisphere TPA and one of the northern hemisphere TPAs are associated with electron and ion precipitation and mostly sunward plasma flow (with shears) relative to their surroundings. Meanwhile, the other TPA in the northern hemisphere is associated with an electron‐only precipitation and antisunward flow relative to its surroundings. Our observations indicate the following: (a) the TPA formation is not limited to northward IMF conditions; (b) the TPAs can be located on both closed field lines rooted in the polar cap of both hemispheres and open field lines connected to the northward field lines draped over one hemisphere of the magnetopause. We believe that the TPAs presented here are the result of both indirect and direct processes of solar wind energy transfer to the high‐latitude ionosphere.

@article{doi1010292021ja029197,
    author = "Park, Jong‐Sun and Shi, Quan and Nowada, Motoharu and Shue, Jih‐Hong and Kim, Khan‐Hyuk and Lee, Dong‐Hun and Zong, Qiugang and Degeling, A. W. and Tian, An Min and Pitkänen, T. and Zhang, Yongliang and Rae, I. J. and Hairston, M. R.",
    title = "Transpolar Arcs During a Prolonged Radial Interplanetary Magnetic Field Interval",
    year = "2021",
    journal = "Journal of Geophysical Research Space Physics",
    abstract = "Abstract Transpolar arcs (TPAs) are believed to predominantly occur under northward interplanetary magnetic field (IMF) conditions with their hemispheric asymmetry controlled by the Sun‐Earth (radial) component of the IMF. In this study, we present observations of TPAs that appear in both the northern and southern hemispheres even during a prolonged interval of radially oriented IMF. The Defense Meteorological Satellite Program (DMSP) F16 and the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellites observed TPAs on the dawnside polar cap in both hemispheres (one TPA structure in the southern hemisphere and two in the northern hemisphere) during an interval of nearly earthward‐oriented IMF on October 29, 2005. The southern hemisphere TPA and one of the northern hemisphere TPAs are associated with electron and ion precipitation and mostly sunward plasma flow (with shears) relative to their surroundings. Meanwhile, the other TPA in the northern hemisphere is associated with an electron‐only precipitation and antisunward flow relative to its surroundings. Our observations indicate the following: (a) the TPA formation is not limited to northward IMF conditions; (b) the TPAs can be located on both closed field lines rooted in the polar cap of both hemispheres and open field lines connected to the northward field lines draped over one hemisphere of the magnetopause. We believe that the TPAs presented here are the result of both indirect and direct processes of solar wind energy transfer to the high‐latitude ionosphere.",
    url = "https://doi.org/10.1029/2021ja029197",
    doi = "10.1029/2021ja029197",
    openalex = "W3167885955",
    references = "doi1010292020ja027991"
}

Abstract Industrialization has raised the concentration of carbon dioxide (CO 2) in Earth's atmosphere by half since 1770, posing a risk from ocean acidification to global biodiversity, including phytoplankton that synthesize approximately (∼) 50% of planetary oxygen. This risk is estimated here from the fossil record and implications for our energy and economic future are explored. Over the last 534 million years (Myr), 50 extinction events present as peaks of genus loss‐and‐recovery cycles, each spanning ∼3–40 Myr. Atmospheric CO 2 concentration oscillates with percent genus loss, leading in phase by ∼4 Myr and sharing harmonic periodicities at ∼10, 26 and 63 Myr. Over the last 210 Myr, where data resolution is highest, biodiversity loss is correlated with atmospheric CO 2 concentration, but not with long‐term global temperature nor with marginal radiative forcing of temperature by atmospheric CO 2. The end‐Cretaceous extinction of the dinosaurs is anomalous, occurring during a 20‐million year depression in atmospheric CO 2 concentration and rising global temperature. Today's atmospheric CO 2 concentration, ∼421 parts per million by volume (ppmv), corresponds in the most recent marine fossil record to a biodiversity loss of 6.39%, implying that contemporary anthropogenic CO 2 emissions are killing ocean life now. The United Nations Intergovernmental Panel on Climate Change projects that unabated fossil fuel use could elevate atmospheric CO 2 concentration to 800 ppmv by 2100, approaching the 870 ppmv mean concentration of the last 19 natural extinction events. Reversing this first global anthropogenic mass extinction requires reducing net anthropogenic CO 2 emissions to zero, optimally by 2% per year starting immediately.

@article{doi1010292022ef003336,
    author = "Davis, William J.",
    title = "Mass Extinctions and Their Relationship With Atmospheric Carbon Dioxide Concentration: Implications for Earth's Future",
    year = "2023",
    journal = "Earth s Future",
    abstract = "Abstract Industrialization has raised the concentration of carbon dioxide (CO 2) in Earth's atmosphere by half since 1770, posing a risk from ocean acidification to global biodiversity, including phytoplankton that synthesize approximately (∼) 50\% of planetary oxygen. This risk is estimated here from the fossil record and implications for our energy and economic future are explored. Over the last 534 million years (Myr), 50 extinction events present as peaks of genus loss‐and‐recovery cycles, each spanning ∼3–40 Myr. Atmospheric CO 2 concentration oscillates with percent genus loss, leading in phase by ∼4 Myr and sharing harmonic periodicities at ∼10, 26 and 63 Myr. Over the last 210 Myr, where data resolution is highest, biodiversity loss is correlated with atmospheric CO 2 concentration, but not with long‐term global temperature nor with marginal radiative forcing of temperature by atmospheric CO 2. The end‐Cretaceous extinction of the dinosaurs is anomalous, occurring during a 20‐million year depression in atmospheric CO 2 concentration and rising global temperature. Today's atmospheric CO 2 concentration, ∼421 parts per million by volume (ppmv), corresponds in the most recent marine fossil record to a biodiversity loss of 6.39\%, implying that contemporary anthropogenic CO 2 emissions are killing ocean life now. The United Nations Intergovernmental Panel on Climate Change projects that unabated fossil fuel use could elevate atmospheric CO 2 concentration to 800 ppmv by 2100, approaching the 870 ppmv mean concentration of the last 19 natural extinction events. Reversing this first global anthropogenic mass extinction requires reducing net anthropogenic CO 2 emissions to zero, optimally by 2\% per year starting immediately.",
    url = "https://doi.org/10.1029/2022ef003336",
    doi = "10.1029/2022ef003336",
    openalex = "W4381886994",
    references = "alvarez1980extraterrestrial, doi101016s0009254199000819, doi101017s1473550417000040, doi101038242032a0, doi101038nature09678, doi101038s41467021237540, doi101038s43017021002594, doi101089ast20192043, doi101126sciadv1400253, doi101126science1177265, doi101126science22346411135, doi101126science2815374200, doi101126science2815374237, doi1011302019254214, doi10230720033020, doi10384720418213ab12eb, openalexw1520428197, openalexw2530597942"
}

Abstract The production rates of cosmogenic radionuclides, such as 10 Be, 14 C, and 36 Cl, in the Earth's atmosphere vary with the geomagnetic field and solar activity. For the first time, the production rates of several cosmogenic nuclides are estimated for the past 100 ka based on global, time‐dependent geomagnetic field models and a moderate solar‐activity level. In particular, the production rates were high with no notable latitudinal dependence during the Laschamps geomagnetic excursion (41 ka BP). The mean global production of 10 Be over the Laschamps excursion was more than two times greater than the present‐day one, whereas the increase was 1.9 times for the Norwegian‐Greenland Sea excursion (∼65 ka), and only 1.3 times for the Mono Lake/Auckland excursion (∼34 ka). All analyzed geomagnetic field models covering the past 100 ka, including the modern and Holocene epochs, lead to hemispheric asymmetry in the production rates, persistent overall time ranges, and reflected in the time‐averaged nuclide production rates. Production rates predicted by the geomagnetic field models are in good agreement with actual measurements from ice cores and sediment records. These global, long‐term production rates are important for a wide range of studies that employ cosmogenic nuclides as a proxy/tracer of different Earth system processes.

@article{doi1010292022ja031158,
    author = "Panovska, Sanja and Poluianov, Stepan and Gao, Jiawei and Korte, Monika and Mishev, Alexander and Shprits, Yuri and Usoskin, Ilya",
    title = "Effects of Global Geomagnetic Field Variations Over the Past 100,000 Years on Cosmogenic Radionuclide Production Rates in the Earth's Atmosphere",
    year = "2023",
    journal = "Journal of Geophysical Research Space Physics",
    abstract = "Abstract The production rates of cosmogenic radionuclides, such as 10 Be, 14 C, and 36 Cl, in the Earth's atmosphere vary with the geomagnetic field and solar activity. For the first time, the production rates of several cosmogenic nuclides are estimated for the past 100 ka based on global, time‐dependent geomagnetic field models and a moderate solar‐activity level. In particular, the production rates were high with no notable latitudinal dependence during the Laschamps geomagnetic excursion (41 ka BP). The mean global production of 10 Be over the Laschamps excursion was more than two times greater than the present‐day one, whereas the increase was 1.9 times for the Norwegian‐Greenland Sea excursion (∼65 ka), and only 1.3 times for the Mono Lake/Auckland excursion (∼34 ka). All analyzed geomagnetic field models covering the past 100 ka, including the modern and Holocene epochs, lead to hemispheric asymmetry in the production rates, persistent overall time ranges, and reflected in the time‐averaged nuclide production rates. Production rates predicted by the geomagnetic field models are in good agreement with actual measurements from ice cores and sediment records. These global, long‐term production rates are important for a wide range of studies that employ cosmogenic nuclides as a proxy/tracer of different Earth system processes.",
    url = "https://doi.org/10.1029/2022ja031158",
    doi = "10.1029/2022ja031158",
    openalex = "W4385326694",
    references = "doi1010292021gc010261"
}

Abstract During the Earth's magnetic reversal, the dipole component of the magnetic field weakens, and the non‐dipole component becomes dominant, resulting in a far more complex magnetospheric topology than that of a dipole. In this study, we used a particle tracing technique to investigate the motion of ions within an irregular magnetosphere during the Matuyama‐Brunhes magnetic polarity reversal. Compared to the scenario in which the geomagnetic field is dominated by a dipole component, earthward‐moving particles can be hardly “trapped” in the inner magnetosphere when the geomagnetic field experiences the polarity reversal, and particles can directly precipitate into the Earth's atmosphere on a global scale. It suggests that under an irregular magnetospheric configuration, the traditional trapped region of particles (e.g., radiation belt or ring current) no longer exists.

@article{doi1010292023gl103843,
    author = "Gong, Fan and Yu, Yiqun and Bai, Kun and Cao, Jinbin and Wei, Yong",
    title = "On the Particle Motion in Paleo‐Magnetosphere During the Geomagnetic Polarity Reversal",
    year = "2023",
    journal = "Geophysical Research Letters",
    abstract = "Abstract During the Earth's magnetic reversal, the dipole component of the magnetic field weakens, and the non‐dipole component becomes dominant, resulting in a far more complex magnetospheric topology than that of a dipole. In this study, we used a particle tracing technique to investigate the motion of ions within an irregular magnetosphere during the Matuyama‐Brunhes magnetic polarity reversal. Compared to the scenario in which the geomagnetic field is dominated by a dipole component, earthward‐moving particles can be hardly “trapped” in the inner magnetosphere when the geomagnetic field experiences the polarity reversal, and particles can directly precipitate into the Earth's atmosphere on a global scale. It suggests that under an irregular magnetospheric configuration, the traditional trapped region of particles (e.g., radiation belt or ring current) no longer exists.",
    url = "https://doi.org/10.1029/2023gl103843",
    doi = "10.1029/2023gl103843",
    openalex = "W4381996413",
    references = "doi1010292021gc010261"
}

The Late Ordovician Mass Extinction was the earliest of the 'big' five extinction events and the earliest to affect the trajectory of metazoan life. Two phases have been identified near the start of the Hirnantian period and in the middle. It was a massive taxonomic extinction, a weak phylogenetic extinction and a relatively benign ecological extinction. A rapid cooling, triggering a major ice age that reduced the temperature of surface waters, prompted a drop in sea level of some 100 m and introduced toxic bottom waters onto the shelves. These symptoms of more fundamental planetary processes have been associated with a range of factors with an underlying driver identified as volcanicity. Volcanic eruptions, and other products, may have extended back in time to at least the Sandbian and early Katian, suggesting the extinctions were more protracted and influential than hitherto documented.

@article{doi101093nsrnwad319,
    author = "Harper, David A. T.",
    title = "Late Ordovician Mass Extinction: Earth, fire and ice",
    year = "2023",
    journal = "National Science Review",
    abstract = "The Late Ordovician Mass Extinction was the earliest of the 'big' five extinction events and the earliest to affect the trajectory of metazoan life. Two phases have been identified near the start of the Hirnantian period and in the middle. It was a massive taxonomic extinction, a weak phylogenetic extinction and a relatively benign ecological extinction. A rapid cooling, triggering a major ice age that reduced the temperature of surface waters, prompted a drop in sea level of some 100 m and introduced toxic bottom waters onto the shelves. These symptoms of more fundamental planetary processes have been associated with a range of factors with an underlying driver identified as volcanicity. Volcanic eruptions, and other products, may have extended back in time to at least the Sandbian and early Katian, suggesting the extinctions were more protracted and influential than hitherto documented.",
    url = "https://doi.org/10.1093/nsr/nwad319",
    doi = "10.1093/nsr/nwad319",
    openalex = "W4389940884",
    references = "doi101016jearscirev201804003, doi101016jearscirev2020103280, doi101016s0016787876800077, doi101111pala12334"
}

Evolution has not been a simple path. Since the first appearance of complex life, there have been several mass extinctions on Earth. This was exemplified by the most severe event during the Phanerozoic, the end-Permian mass extinction that occurred 252 million years ago and saw a loss of 90% and 70% of all marine and terrestrial species, respectively. Such mass extinctions have entirely reset ecosystems. Increasing evidence points to the massive eruption and crustal emplacement of magmas associated with large igneous provinces (LIPs) as key drivers of these events. Understanding how LIP events disrupted global biogeochemical cycles is of prime importance, especially as humans alter the atmosphere and biosphere today. We explore the cascading impacts of LIP events on global climate, oceans, and land—including runaway greenhouses, the release of toxic metals to the environment, the destruction of the ozone layer, and how global oceans are driven to anoxic and acidic states—all of which have parallels in the consequences of modern industrialisation.

@article{doi102138gselements195276,
    author = "Grasby, Stephen E. and Bond, David P.G.",
    title = "How Large Igneous Provinces Have Killed Most Life on Earth—Numerous Times",
    year = "2023",
    journal = "Elements",
    abstract = "Evolution has not been a simple path. Since the first appearance of complex life, there have been several mass extinctions on Earth. This was exemplified by the most severe event during the Phanerozoic, the end-Permian mass extinction that occurred 252 million years ago and saw a loss of 90\% and 70\% of all marine and terrestrial species, respectively. Such mass extinctions have entirely reset ecosystems. Increasing evidence points to the massive eruption and crustal emplacement of magmas associated with large igneous provinces (LIPs) as key drivers of these events. Understanding how LIP events disrupted global biogeochemical cycles is of prime importance, especially as humans alter the atmosphere and biosphere today. We explore the cascading impacts of LIP events on global climate, oceans, and land—including runaway greenhouses, the release of toxic metals to the environment, the destruction of the ozone layer, and how global oceans are driven to anoxic and acidic states—all of which have parallels in the consequences of modern industrialisation.",
    url = "https://doi.org/10.2138/gselements.19.5.276",
    doi = "10.2138/gselements.19.5.276",
    openalex = "W4389946000",
    references = "doi101038227930a0, doi101038s43017021002594"
}

Abstract The long‐term variation of the geomagnetic field is a key constraint for unraveling the geodynamo processes and the evolution of Earth's deep interior. However, the geomagnetic reversal pattern during the Ediacaran–Cambrian transition remains elusive. Here we present an integrated magneto‐ and cyclo‐stratigraphic study of a ∼1.8‐Myr‐long, late Ediacaran succession in Newfoundland, Canada. We obtained a reversal frequency of 10–12 Myr −1, documenting a hyperactively reversing geodynamo during the late Ediacaran. Together with the updated reversal records and paleointensity data sets, we propose a >70‐Myr‐long interval of geomagnetic reversal hyperactivity before the Ordovician Reversed Superchron, forming a hyperactivity‐superchron couplet that recurs in the mid‐Paleozoic and Mesozoic. These findings suggest that the onset of the ∼200‐Myr‐long cycle in geomagnetic field behavior has occurred since at least ∼570 Ma, earlier than previously envisaged.

@article{doi1010292025gl118030,
    author = "Shen, Fuyun and Wen, Bin and McCausland, P. J. A. and Gong, Zheng and Zhu, Zongmin and Liu, Fangzheng and Wang, Jingyi",
    title = "A >70‐Myr‐Long Geomagnetic Field Reversal Hyperactivity Across the Ediacaran‐Cambrian Transition",
    year = "2025",
    journal = "Geophysical Research Letters",
    abstract = "Abstract The long‐term variation of the geomagnetic field is a key constraint for unraveling the geodynamo processes and the evolution of Earth's deep interior. However, the geomagnetic reversal pattern during the Ediacaran–Cambrian transition remains elusive. Here we present an integrated magneto‐ and cyclo‐stratigraphic study of a ∼1.8‐Myr‐long, late Ediacaran succession in Newfoundland, Canada. We obtained a reversal frequency of 10–12 Myr −1, documenting a hyperactively reversing geodynamo during the late Ediacaran. Together with the updated reversal records and paleointensity data sets, we propose a >70‐Myr‐long interval of geomagnetic reversal hyperactivity before the Ordovician Reversed Superchron, forming a hyperactivity‐superchron couplet that recurs in the mid‐Paleozoic and Mesozoic. These findings suggest that the onset of the ∼200‐Myr‐long cycle in geomagnetic field behavior has occurred since at least ∼570 Ma, earlier than previously envisaged.",
    url = "https://doi.org/10.1029/2025gl118030",
    doi = "10.1029/2025gl118030",
    openalex = "W4417100829",
    references = "doi101017s1473550417000040"
}