The Correlation Between Impact Crater Ages And

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Cosmic Impacts and Global Change 1

The Correlation Between Impact Crater Ages and Chronostratigraphic Boundary Dates Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020

R. B. Firestone? University of California, Department of Nuclear Engineering, Berkeley, 94720,USA

Accepted XXX. Received YYY; in original form ZZZ

ABSTRACT

The accurately measured ages of 89 large impact craters and layers were compared with the boundary dates for Periods, Epochs and Ages of the Geological Time Scale by a weighted least squares ﬁt. They are highly correlated with a χ2/ f =0.63. A Monte Carlo simulation of randomly chosen crater ages gives a >99.8% probability that this result is not random. No craters are found in the oceans or, until recently, in ice which collectively cover 80% of Earth’s surface indicating that far more impacts have occurred than are known. Multiple impacts cluster near the times of boundary dates so, based on the observed cluster sizes assuming a binomial distribution, it was determined that the average cluster multiplicity is ﬁve. Comparison of the impact ages with the dates of the great extinctions revealed a strong correlation with χ2/ f =0.36 and a multiplicity of 8-9 impacts. It is shown that volcanism, although correlated with boundary dates, is a continuous process unrelated to sudden extinctions. During the past 125 Ma the rate of global change and the impact rate have increased dramatically as the Earth passes near the OB star association. Multiple impacts 12.9 ka ago ended the Pleistocene epoch at the onset of the Younger Dryas (YD) causing worldwide extinctions. The date and extent of the YD impact may be consistent with a 62 Ma cycle of major impact events. During the Holocene 20 crater, airburst, and impact tsunami chevron ages correspond to dates of global cooling with a χ2/ f =0.75 and >99% probability. Future impacts could reverse global warming or even induce next ice age. Key words: Earth – meteors – comets – supernovae

1 INTRODUCTION A large number of impact craters and layers have been identified, many with precisely measured ages. The larger craters, >1 km The geological history of Earth can be described by ≈116 pe- in diameter, would have produced significant local to worldwide riods, epochs, and ages as shown on the International Chronos- damage. Both the K-Pg and P-Tr extinctions are coincident with tratigraphic Chart Version 2020/03 which is maintained by the multiple land impacts yet many additional, undiscovered impacts International Commission on Stratigraphy Cohen et al.(2018). must have occurred near those times in the oceans or glaciers that The boundaries between the ages are well dated and are asso- cover 80% of the Earth’s surface. No craters are found in water or, ciated with sudden changes in climate, extinctions, and the evo- until very recently, in ice where the evidence is quickly erased by lution of new flora and fauna. The major extinctions are also ocean currents and subduction into Earth’s mantel. The average age well dated in marine fossil records Sepkoski et al.(2002) which of the ocean floor is only ≈60 Ma Williams et al.(2020). sometimes vary from the chronostratigraphic dates. The sudden- In this work I will investigate the statistical correlation between ness of these changes suggests that they are due to catastrophic the chronostratigraphic boundary, marine extinction and volcanic events such as major volcanic eruptions, meteorite impacts, or eruption dates, and the ages of impact craters and layers. Airbursts gamma ray bursts. Both the Cretaceous–Paleogene (K–Pg) and Per- and impacts during the Holocene will be investigated to infer the mian–Triassic (P-Tr) extinction events have many proponents who likelihood of future impacts that could change the global environ- argue they were caused by impacts, while others argue the cause ment. was volcanism. Still others have argued that impacts enhance large volcanic eruptions Rampino & Caldeira(1992); Hagstrum(2005); Meschede et al.(2011); Renne et al.(2015). Rampino & Caldeira 2 STATISTICAL METHODS (2018) have linked 10 of the past 11 extinction events to either flood-basalt eruptions or to large body impacts. The crater and impact layers have been compared to the boundary dates by a standard weighted χ2 analysis. This method rigorously ORIGINAL UNEDITEDdetermines whether MANUSCRIPT the two sets of data coincide within the un- ? Contact e-mail: rbfi[email protected] certainties assigned by the authors to the data. Both data sets are

Table 1. Compilation of precise crater and impact layer ages and their nearest chronostratigraphic boundary dates.

Timeline Boundary Date (Ma) Associated crater and impact layer ages (Ma)

Chibanian/Calabrian 0.774±0.020 Australasian strewn field Jourdan et al.(2019) 0.788 ±0.003, Belize strewn field Schwarz et al. Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020 (2020) 0.769±0.016, Pantasma Rochette et al.(2019) 0.815 ±0.011, Darwin Schmieder & Kring (2020) 0.816±0.007 Calabrian/Gelasian 1.80±0.05 Tenoumer Schultze et al.(2016) 1.57 ±0.14 Pliocene/Pleistocene 2.58±0.05 Eltanin impact layer Goff et al.(2012) 2.51 ±0.07 Pleistocene/Zanclean 3.600±0.0020 El’gygytgyn Schmieder & Kring(2020) 3.65 ±0.08, Mar del Plata impact layer Schmieder & Kring (2020) 3.37±0.10, Roter Kamm Schmieder & Kring(2020) 3.8 ±.3 Pliocene/Miocene 5.333±0.0020 Karla Beech et al.(2018) 5 ±1, Bahai Blanca impact layer Schmieder & Kring(2020) 5.38 ±0.05, Tsenkher KOMATSU et al.(2017) 4.9 ±0.9 Serravalllian/Langhian 13.82±0.20 Riesa Schmieder et al.(2018) 14.59 ±0.20, Steinheima Schmieder et al.(2018) 14.59 ±0.20 Langhian/Burdigalian 15.97±0.20 Takamatsu Miura et al.(2000) 15.3 ±0.2 Miocene/Oligocene 23.03±0.20 Haughton Jessberger(1988) 23.4 ±1.0 Chattian/Rupelian 27.82±0.20 Libyan Desert glass Bigazzi & Michele(1996) 28.5 ±0.8 Eocene/Oligocene 33.9±0.5 Chesapeake Bay Assis Fernandes et al.(2019) 34.86 ±0.32, Popigai Wielicki et al.(2014) 33.9 ±1.3 Priabonian/Bartonian 37.71±0.20 Wanapitei Schmieder & Kring(2020) 37.7 ±1.2, Mistastin Sylvester et al.(2013) 37.83 ±0.05 Bartonian/Lutetian 41.2±0.5 Logoisk Beech et al.(2018) 42.3 ±1.1 Lutetian/Ypresian 47.8±0.5 Montagnais Beech et al.(2018) 50.50 ±0.76, Kamenska Beech et al.(2018) 49.0 ±0.2, Guseva Beech et al.(2018) 49.0 ±0.2, Ragozinka Beech et al.(2018) 46 ±3 Ypresian/Thanetian 56.0±0.5 Impact layer Schaller et al.(2019) 54.2 ±2.5, Marquez McHone & Sorkhabi(1994) 58 ±3 Cretaceous/Paleogene 66.0±0.5 Chicxulub Schmieder & Kring(2020) 66.052 ±0.043, Boltysh Pickersgill(2019) 65.47 ±0.21 Maastricrichtian/Campanian 72.1±0.2 Karaa Schmieder & Kring(2020) 70.7 ±2.2, Ust-Karaa Beech et al.(2018) 70.7 ±2.2 Hetonianb /Campanian 77.1±2.0 Lappajärvi Kenny et al.(2019) 77.85 ±0.78, Manson Schmieder & Kring(2020) 75.9 ±0.1 Campanian/Santonian 83.6±0.2 Wetumpka Wartho et al.(2012) 84.4 ±1.4 Santonian/Coniacian 86.3±0.5 Suvasvesi N Schmieder et al.(2016b) 85 ±2 Coniacian/Turonian 89.8±0.3 Dellen Beech et al.(2018) 89.0 ±2.7 Cenomanian/Albian 100.5±0.5 Deep Bay Beech et al.(2018) 99 ±4, Avak Kirschner et al.(1992) 100 ±5 Aptian/Barremian 125.0±1.0 Mien Schmieder & Kring(2020) 122.4 ±2.3, Vargeao Beech et al.(2018) 123.0 ±1.4, Tookoonooka Schmieder & Kring(2020) 125 ±1 Barremian/Hauterivan 129.4±1.0 Talundilly Beech et al.(2018) 128 ±5 Valanginian/Berriasian 139.8±1.0 Mjølnir Beech et al.(2018) 142.0 ±2.6, Dellen Mark et al.(2014) 140.8 ±0.5, Steen River McGregor et al.(2020b) 141 ±4 Jurassic/Cretaceous 145.0±1.0 Morokweng Beech et al.(2018) 145.0 ±0.8, Gosses Bluff Beech et al.(2018) 142.5 ±0.8 Tithonian/Kimmeridgian 166.1±1.2 Zapadnaya Rampino & Caldeira(2015) 165 ±5 Bathonian/Bajocian 168.3±1.3 Obolon’ Beech et al.(2018) 169 ±7 Pliensbachian/Sinemunian 190.8±1.0 Puchezh-Katunki Holm-Alwmark et al.(2019) 194 ±2 Hettangian/Sinemurian 199.3±0.3 Gow Lake Schmieder & Kring(2020) 196.8 ±9.9 Rhaetian/Norian 208.5±2.0 Manicouagan Beech et al.(2018) 214 ±1, Bristol spherule layer Walkden et al.(2002) 214.0 ±2.5, Rochechouart Schmieder & Kring(2020) 206.9 ±0.3 Norian/Camian 227±2 Saint Martin Schmieder & Kring(2020) 227.8 ±0.9, Paasselkä Schwarz et al.(2015) 231.0 ±2.2 Permian/Triassic 251.902±0.024 Araguainha Hauser et al.(2019) 251.5 ±2.9 Kungurian/Artinskian 283.5±0.6 Clearwater West Meier & Holm-Alwmark(2017) 286.2 ±2.2 Devonian/Carboniferous 358.9±0.4 Woodleigh Beech et al.(2018) 364 ±8, Lockne Tillberg et al.(2019) 356.6 ±6.7 Frasnian/Givetian 382.7±1.6 Alamo Pinto & Warme(2007) 382 ±4, Ilyinets Beech et al.(2018) 378 ±5, Siljan Reimold et al. (2005) 377±2, Kaluga Beech et al.(2018) 380 ±5 Givetian/Eifelian 387.7±0.8 Nicholson McGregor et al.(2018) 387 ±5 Himantian/Katian 445.2±1.4 Pilot Bottomley et al.(1990) 445 ±2, Calvin Schmieder & Kring(2020) 451 ±7 Katian/Sandbian 453.0±0.7 Brent McGregor et al.(2020a) 453 ±3, Lac La Moinerie McGregor et al.(2019) 453 ±5 Sandbian/Darriwilian 458.4±0.9 Kardla Jourdan et al.(2012) 455 ±1, Tvaren Jourdan et al.(2012) 462 ±5 Darriwilian/Dapingian 467.3±1.1 Clearwater East Jourdan et al.(2012) 465 ±5 Ordovician/Cambrian 485.4±1.9 Carswell Alwmark et al.(2017) 485.5 ±1.5 Phanerozoic/Precambrian 541.0±1.0 Gardnos Kalleson et al.(2009) 546 ±5 Ediacaran/Cryogeian 635±30 Strangways Spray et al.(1999) 646 ±42, Sääksjärvi Kenny et al.(2020) 608 ±8 Cryogenian/Tonian 720±50 Suvasvesi N Schmieder et al.(2016b) 720 ±10, Jänisjärvi Jourdan et al.(2012) 687 ±5 Tonian/Stenian 1000±50 Highbury Gumede et al.(1998) 1034 ±13 Stenian/Ectasian 1200±50 Impact layer Stac Fada Parnell et al.(2011) 1177 ±5, Keurusselka Schmieder et al.(2016a) 1151 ±10 Statherian/Orosirian 1800±50 Sudbury Schmieder & Kring(2020) 1849.53 ±0.21 Orosirian/Rhyacian 2050±50 Vredefort Jourdan et al.(2012) 2023 ±4 Rhyacian/Siderian 2300±50 Yarrabubba Erickson et al.(2020) 2229 ±5 Proterozoic/Archean 2500±50 Wittenoom spherule layer Rasmussen et al.(2005) 2490 ±10, Reivilo spherule layer Schmieder & Kring(2020) 2541 ±18 Mesoarchean/Paleoarchaen 3200±50 Archean impact layer Schmieder & Kring(2020) 3234 ±5 a Pairs of craters assigned a common date. Only one value was used in the statistical analysis. ORIGINALb The Hetonian Japanese stage Cohen et al. (2018UNEDITED) has been associated with a major extinction horizonMANUSCRIPT and is added here. Cosmic Impacts and Global Change 3 Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020

Figure 1. Comparison of crater ages (•) and impact layer ages (•) with the Geological time line. The black lines indicate period demarcations, solid red lines indicate epochs, and dotted red lines ages Cohen et al.(2018). The impact energy is based on calculation Toon et al.(1997) assuming either an asteroid traveling at 15ORIGINAL km/s with a density of 2.5 g/cm3 or a comet withUNEDITED a velocity of 50 km/s and a density of 1 g/cm 3.MANUSCRIPT 4 R. B. Firestone subject to systematic errors that will tend to increase the χ2 value. The likelihood that the χ2 analysis is not random has been tested by a Monte Carlo simulation where a large number of random crater age sets of similar precision are generated and compared with the Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020 boundary dates by χ2 analyses. Comparison of the experimental χ2 value with the distribution of random χ2 values determines the likelihood that the experimental value is a random result. This analysis cannot determine whether the impact crater and layer ages exactly coincide with the boundary dates, but only that they are proximate to the boundary dates.

2.1 Data selection There are no complete, up to date databases of crater ages avail- able so for this paper the most recent precise dates have been 2 obtained through an extensive literature search with the help of Figure 2. Distribution of weighted χ /f values comparing random crater several compilations Jourdan et al.(2012); Beech et al.(2018); ages with boundary dates. Schmieder & Kring(2020). The crater candidates were selected from a list of ≈207 known impact craters Moilanen(2019) of which ≈180, >1 km in diameter, can be assumed to cause signiﬁcant environmental damage. Among the >1 km craters 76 had ages that were measured with comparable precisions to boundary dates and were selected for use in this analysis. In addition 13 impact layers with no known associated crater but having ages of comparable precision were included. Each selected crater and impact layer age was matched to the nearest chronostratigraphic boundary date Cohen et al.(2018) as summarized in Table1 and shown in Fig.1.

2.2 Weighted χ2 analysis

The correlation between the crater and impact layer ages and their Figure 3. Comparison of the observed probability of clusters 1-4 land impact uncertainties, tc ± ∆tc, and the geological age boundary dates and craters (•) with the expected probability distribution for clusters of 4-7 global their uncertainties, tb ± ∆tb, has been determined by a weighted impacts assuming that 75% of all impacts are into the oceans or ice sheets. χ2 analysis as shown in Eq.1 where N is the number of crater and impact layer ages that were compared and f = N − 1. the experimental crater and impact layer dataset and gave χ2/ f val- N Õ (t − t )2 ues ranging from 0.75-210 with no set lower than the experimental χ2/ f = b c (N − 1) (1) 2 value. The likelihood that the observed correlation between crater (∆tb + ∆tc) 1 ages and boundary dates is random thus ≤0.2%. The distribution of 2 The uncertainties in the boundary dates, ∆tb, were taken from the Monte Carlo simulated, weighted χ / f values is shown in Fig.2. chart, when specified, or estimated from the precision of the given The distribution is double peaked and very different from a normal value as given in Table1. This analysis determines definitively distribution. whether the crater ages and boundary dates agree within their uncertainties in which case, assuming a normal distribution, χ2/ f ≈ 0.75 would have a 96% probability of a direct correlation. The weighted 2.4 Multiplicity of impacts 2 2 experimental χ analysis gave a χ / f =0.63 indicating with 99.8% The database of known impact craters represents only a small frac- probability that there is a strong correlation between the chronos- tion of the Earth impact events. For example 5185 impact craters tratigraphic boundary dates and the impact crater and layer ages. ≥20 km in diameter have been identified on the moon Head et al. (2010); Kadish et al.(2011) which suggests that ≈70,000 large impacts must have occurred on Earth. The vast majority of the im- 2.3 Monte Carlo simulation pacts occurred very early in Earth’s history and their associated The observed χ2/ f value can not be assumed to follow a normal dis- craters were erased by geological processes. All of the known im- tribution so in order to determine the reliability of the correlation pact craters are found on land with the exceptions of Mjølnir crater a Monte Carlo simulation was performed. Five hundred random, which is found in the Barents Sea and the Chicxulub crater which identical sized sets of hypothetical crater ages were generated. The at the time of the impact was in the ocean Scotese(2004). The simulation was constrained to ages <500 Ma to avoid the region Eltanin impact layer was found near the southeast Pacific Ocean where the chronostratigraphic dates becomes sparse and a random yet no crater has been found. The lack of existing ocean craters selection of ages would be expected to give poor agreement with the is compounded by the fact that no part of the ocean crust is crater ages. Each age was randomly assigned an uncertainty corre- older that 180 Ma Wünnemann et al.(2010) with an average age spondingORIGINAL to the range of uncertainties associated UNEDITED with the observed of 60 Ma Williams MANUSCRIPT et al.(2020). Until recently Kjær et al.(2018); ages. The 500 random data sets were analyzed in the same way as Klokočník et al.(2020), no craters were known in glaciers. Ap- Cosmic Impacts and Global Change 5 proximately 80% of Earth’s surface is covered by water or ice so, although 180 large craters have been found on land, many more unrecorded impacts must have occurred in the sea and ice. The unobserved impacts must follow the same temporal distribution as Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020 the known impacts so each boundary date must be associated with many impacts. A total of 51 boundary dates are statistically associated with impacts. Among these dates 24 were associated with a single crater or impact layer age, 18 with two ages, 8 with three ages, and 2 with four ages. For clusters of N impacts the number, NL, of impacts that occur on land is given by a binomial distribution as shown in Eq.2 N−N NL fL(1 − fL) L N! NL = N (2) NL!(N − NL)! where fL is the fraction of Earth’s area that is land. Simplistically Figure 4. Distribution of the expected energy release from clusters of five fL=0.2 but if the natural distribution of objects striking the Earth impacts in mT (TNT) based on a random sampling of the observed crater is not uniform then the effective fL may vary. The land impact size distribution. probability distribution for clusters of 4-7 impacts is shown in Fig.3 where fL is a free parameter least squares fit to agree with N impacts. The best fit was found for a cluster of five impacts where fL=0.265 although the actual number of impacts in each cluster must vary. (1997) and is ≈ 10, 000 times more powerful than the largest hydro- This suggests that there would have been ≈700 impacts globally, gen bomb ever exploded. An impact of this size would be expected including the 180 known land impacts, and ≈140 impact clusters. to cause regional catastrophic damage. Approximately 16 impacts comparable to or more powerful than the Chicxulub impact with energy releases > 8.4 × 108 mT must have occurred in the oceans leading to global catastrophes. The cumulative effect of a cluster 3 DISCUSSION of impacts will vary. The distribution of total energy release from The strong correlation between the ages of impact craters and the five impacts is shown in Fig.4. About 17% of the clusters release 6 dates of chronostratigraphic boundaries is remarkable. It indicates < 10 mT of energy, enough for only localized damage, 58% re- 6 8 that impacts play an important role in global change. The clusters lease 10 −10 mt, sufficient to cause widespread damage, and 25% 8 of impacts do not necessarily occur simultaneously as seen for the release > 10 mT, enough to cause a global catastrophe. About 83% impacts associated with the Chibanian/Calabrian boundary dated to of impact clusters could cause ecological change similar to those 774 ka ago. The Austalasian strewn field is dated to 788±3 ka, the recorded in the Chronostratigraphic Chart. If 140 clusters are ex- Belize strewn field to 769±16 ka, Darwin crater to 816±7 ka ago and pected this suggests that ≈116 should be represented on the chart Pantasma crater to 815±11 ka. The Chibanian/Calabrian boundary consistent with the reported number of ages. date corresponds to the Brunhes-Matuyama magnetic field rever- sal that occurred 776±14 ka ago Galheb et al.(2019) which is not believed to have been caused by an impact. The two strewn fields have statistically consistent dates and an ≈15 km Austalasian im- 3.2 Possible causes of the correlation of impacts with pact crater is believed to be buried under the Bolaven volcanic geological change field Sieh et al.(2020). This suggests that there are three craters The strong correlation between clusters of impact events and the associated with the Chibanian/Calabrian boundary date and likely boundary dates shows that they are intimately connected. The clus- ≈9 more impacts should have occurred in the ocean at that time. tering of impacts suggests that they are triggered by astronomical Remarkably there was no major environmental change at this time events. Several hypotheses are proposed here as the possible triggers although the date of the Austalasian strewn field does correspond of the multiple impacts. to the onset of the 100 ka Milankovich glacial cycle Broecker et al. (1968). The causes of clusters of impacts and their environmental effects are uncertain. Environmental change is often ascribed to magmatism leading to considerable discussion as to whether mass ex- 3.2.1 Atmospheric breakup of a large comet or meteor tinctions are impact or volcanic in origin. The chronostratigraphic At least three doublet craters, Kara and Ust-Kara, Ries and Stein- boundaries are often determined by geological rather than environ- heim, and Kamensk and Gusev appear to result from the breakup mental considerations so accepted extinction dates do not always of a single object in the atmosphere leading to two craters that form coincide with boundary dates. Major impacts can lead to nearly in close proximity. Similarly, tidal breakup of a large comet, as was instantaneous environmental consequences. The history of impact the case for Shoemaker/Levy on Jupiter Shoemaker et al.(1993), events has repeated itself through time and can predict both the near could account for a chain of more widely separated impacts closely and distant future of our environment on Earth. associated in time. However, those impacts would be aligned in a single direction. Earth’s gravity is much weaker than that of Jupiter so only rarely would a comet tidal breakup have occurred in Earth’s 3.1 Expected Damage from Impact Clusters history Bottke et al.(1997). The known impact craters are randomly TheORIGINAL average observed impact crater is ≈20 kmUNEDITED in diameter which distributed around MANUSCRIPT the Earth so these processes should not be a major corresponds to an energy release of ≈ 5.5 × 105 mT Toon et al. contributor to impact cluster formation. 6 R. B. Firestone

3.2.2 Passing stars Stars passing near the Oort Cloud can eject comets into Earth inter- +15 secting orbits. This may have happened 70−10 ka ago when Scholz’s star passed 2 Ma−1 Bailer-Jones(2017). A companion star to the Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020 Sun, Nemesis Davis et al.(1984); Whitmire & Jackson(1984), is proposed to exist at the edge of the Oort Cloud and could be respon- sible for a group of impacts observed on a ≈26 Ma cycle as proposed by Raup & Sepkoski(1984); Melott & Bambach(2010). Nemesis has been largely discounted although a yet to be discovered Planet X is also proposed to explain the 26 Ma cycle and periodic mass extinctions Whitmire(2015). The action of galactic tidal forces and the passage of the sun through clouds of dense dark matter have also been implicated in perturbing the Oort cloud and generating the 26 Ma cycle Rampino(2015).

3.2.3 Gamma-ray bursts Gamma-ray bursts (GRB) direct a large amount gamma-ray energy in a narrow angle Rhoads(1997). Although Earth’s atmosphere would shield us from distant bursts, GRB less than 10 kpc from Earth could cause catastrophic eﬀects. It has been suggested that the Late Ordovician mass extinction, ≈445 Ma ago, could be the result of a gamma ray burst Thomas et al.(2005). GRB are presumed to be very rare with a 50% chance of one striking Earth in past 500 Ma Piran & Jimenez(2014).

3.2.4 Breakup of large comets in the inner solar system Napier(2015) proposed that large comets are regularly being ejected from the Oort cloud into the solar system where they break up leaving a massive debris field that intersects with Earth’s orbit. Although Figure 5. Top: Comparison of the number of impacts with the number many of these comets are absorbed by Jupiter before reaching Earth, of assigned geological ages per 25 Ma during the past 250 Ma. Bottom: others are broken up by Jupiter’s gravity and scattered into the inner Duration of boundary dates averaged over three successive boundaries for solar system Horner et al.(2010). This scenario produces a cluster the past 50 Ma. of impacts scattered over thousands of years as the debris field dissi- pates. Many of the progenitor comets would be >100 km in diameter and the larger fragments impacting Earth could cause catastrophic γ-ray flux of 1014 ergs/m2. The irradiation comes from a distant environmental changes. This mechanism has been proposed as a point so a small velocity in a fixed direction will be induced on likely cause of the Younger Dryas impact and other less promi- all bodies, including Oort cloud objects. Assuming a density of 1 nent impacts Napier(2019a) in recent years. The combination of g/cm3, a spherical, 1 km radius object would gain a 1 m/s velocity nearby passing stars and supernovae dislodging comets from the component away from the SN origin whereas a 100 km object would Oort Cloud into Earth intersecting orbits provides a promising hy- gain only an 0.01 m/s velocity. Hanslmeier(2017) has proposed pothesis for the generation of clusters of impacts throughout Earth’s that supernovae 13-17 pc from Earth could cause sufficient heating history. of the Oort cloud to cause cometary showers to the inner solar system. They argue that a nearby supernova explosion uniformly heats almost the entire Oort cloud whereas a passing star heats 3.2.5 Passage through the Local Bubble only a small fraction of the cloud. Hanslmeier(2017) estimated During the past 5-10 Ma the Earth has been passing through the Lo- this may have happened ≈30 times over the evolution of the solar cal Bubble Farhang et al.(2019) a region in the spiral arms of our system assuming a uniform distribution of supernovae throughout galaxy with approximately one tenth of the average neutral hydrogen the galaxy. However the recent local supernova rate is ≈10 times as density of the interstellar medium. The local bubble is associated large as the galactic rate Firestone(2014) suggesting that supernova with a series of neighboring bubbles that were cleared and main- <30 pc from Earth were occurring at ≈1 Ma intervals. tained by supernovae and stellar winds from the Scorpius–Centaurus The number of known large impacts and assigned geological Association. The local supernova rate is approximately ten times that ages per 25 Ma interval for the past 250 Ma is shown in Fig.5. Be- of the galaxy as a whole with 23 supernovae explosions within 300 fore ≈125 Ma ago the impact rate was nearly constant with impacts pc of Earth during the past 300 ka Firestone(2014). Benítez et al. occurring on average every 5.3 Ma and geological ages lasting 5.6 (2002) have estimated that ≈20 supernova have exploded <130 pc Ma. During the past ≈125 Ma the impact rate has been rising dra- from Earth during the past 11 million years. matically to an average of 1 large impact per 0.5 Ma during the past A supernova remnant radiates ≈1051 ergs of high energy γ- 10 Ma. The average duration of boundary ages for the past 50 Ma raysORIGINAL over a period of ≈1500 years Firestone( 2014UNEDITED). A SN explosion is also shown in Fig.MANUSCRIPT5. During that time the duration of boundary 30 pc from Earth would irradiate the entire solar system with a ages has decreased by an order of magnitude while the impact rate Cosmic Impacts and Global Change 7 has increased substantially. Discovery of 60Fe in ocean sediment indicates that a near-Earth supernova exploded ≈2.4 Ma ago near the end of Pliocene epoch, 2.58 Ma ago. This date closely corresponds to the age of the Eltanin impact layer, 2.51±0.7 Ma Goff et al. Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020 (2012). Barringer crater, dated to 49±3 ka Phillips et al.(1991), occurred near the time of a SN explosion 140 pc from Earth 44 ka ago Firestone(2014). The Barringer crater age was measured by 36Cl dating which incorrectly assumes that the cosmic ray rate is constant. The radiocarbon record was corrected for past cosmic ray rates Reimer et al.(2013) and assuming this correction is valid for Barringer crater the age becomes 45.5 ka in good agreement with the SN date. Although there is a strong correlation between the in- Figure 6. Large igneous province magma production, corrected for subduc- crease in recent supernovae and impact events the hypothesis that tion, during the past 150 Ma (Preserved in red and corrected for subduction they are caused by supernova heating remains speculative pending in whiteCoffin et al.(2005). more detailed investigation.

as the main cause of the extinctions Keller et al.(2010). However, 3.2.6 Interstellar objects there is little evidence that the climate changed significantly before, during, or after the K-Pg impact Dzombak et al.(2020). In addition to near Earth supernovae, the recent increased im- Large impacts can cause volcanism by antipodal focusing pact rate can also be due to interstellar objects that are expected but the Deccan traps are 5000 km from the Chicxulub antipode. to be abundant in the spiral arms of the galaxy Napier & Clube Coffin et al.(2005) have speculated that a large impact could cause (1979); Clube & Napier(1982). These objects travel freely through massive decompression melting of the mantle or considerable the Local Bubble but could also be jettisoned from the Oort crustal thinning and fracturing forming conduits for mantle ma- clouds of exploding stars. Like Oort cloud comets these objects terial to reach the surface and Khazins & Shuvalov(2019) have can be break up into Earth intersecting orbits. Two such objects, shown that the impact could have triggered the eruption of the Dec- 1I/Oumuamua Bannister et al.(2019) and 2I/Borisov Jewitt & Luu can traps. It is also well established that earthquakes can cause (2019), have been recently discovered crossing the solar system 0.22 volcanic eruptions Manga & Brodsky(2006) and the K-Pg impact AU and 1.9 AU from Earth respectively. It is estimated that several would have produced a magnitude M =9-11 earthquake capable of interstellar objects pass inside the orbit of Earth each year NASA w triggering volcanic eruptions worldwide Richards et al.(2015). (2017) and 10,000 pass inside the orbit of Neptune each day Fraser The Ontong-Java plateau was formed ≈122 Ma ago by the most (2018). It is possible that a supernova might eject planets and other massive volcanic eruptions in the past 150 Ma yet it caused no sig- orbiting objects into interstellar space Fogg(1988). This presents nificant extinction Tarduno et al.(1991). The origin of this eruption an alternative hypothesis to supernova heating for the recent corre- remains undetermined Fitton et al.(2004). It has been proposed that lation of the increase of near Earth supernovae and impact events. it could be due to a large impact event, perhaps at its antipode in the Pacific Ocean Ingle & Coffin(2004), although no evidence has been found to support this argument. The lack of a strong environmental 3.3 Considerations of Volcanism response to the greatest magmatic event in 150 Ma casts doubt on 16 large flood basalts associated with chronostratigraphic bound- the suggestion that volcanic events cause major extinctions. ary dates Kravchinsky(2012a); Courtillot & Renne(2003); The Ordovician/Silurian extinction 444 Ma ago Ling et al. Eldhom & Coffin(2013) are summarized in Table2. The flood (2020) has been attributed to volcanism based on Hg, Mo, basalt ages correlate to boundary dates with a χ2/ f =0.68. and U anomalies and the development of anoxic contdi- Volcanism has long been correlated with major extinction tions Bond & Grasby(2020). The duration of the extinction is esti- events Bond & Wignall(2014) that produce 0.5-44.4 Mkm 3 of mated to be ≈200 ka Ling et al.(2019). A cluster of three modest magma over a few Ma interval. Although this may appear exten- sized craters are also coincident with that time. Significantly, 475 sive, the normal worldwide production of magma from volcanoes, as Ma ago an ≈150 km diameter L-chondrite body broke up in the shown in Fig.6, occurs at the rate of ≈1-2 Mkm3 per Ma Coffin et al. asteroid belt creating a continuous terrestrial bombardment that (2005), excluding an even grater amount generated in the ocean still delivers nearly one third of all meteorites falling to Earth to- trenches. Seldom has the magma flux fluctuated by more than a day Schmitz et al.(2019); Weirich et al.(2012). Five more modest factor of 2 during the past 150 Ma. sized craters have ages between 475-455 Ma suggesting that ≈36 Over the past 150 Ma only the Deccan traps, producing 8.6 additional impacts must have struck the ocean in the period leading Mkm3 of magma in <1 Ma , and the Ontong-Java plateau, pro- up to the Ordovician/Silurian extinction. It is likely that at least one ducing 44.4 Mkm3 of magma in ≈3 Ma, stand out from the back- of these impacts could be as large as the Chicxulub impact. ground rate. The massive Chixculub Cretaceous/Paleogene (K-Pg) The Late Devonian extinction is sometimes attributed to the impact and the eruption of the Deccan traps occurred <100 ka Viluy and other large trap occurrences Kravchinsky(2012b) 370 apart Richards et al.(2015) suggesting that they were nearly simul- Ma ago. However the Viluy traps produced only a relatively minor taneous. A narrow, iridium rich impact layer Alvarez et al.(1980) amount of magma and are unlikely to have induced a major extinc- marks a time when ≈75% of all plants and animals became extinct. tion event. The Alamo impact, comparable in size to the Chicxulub No vertebrate fossils are found above the iridium layer indicating impact, occurred near the time of the Late Devonian extinction. It that the extinctions were instantaneous Pearson et al.(2002). Al- is more plausible that this impact, not magmatism, caused the Late thoughORIGINAL the vertebrate extinctions were clearly UNEDITED caused by the impact Devonian extinction MANUSCRIPT and possibly activated the Viluy traps. the nearly simultaneous episode of magmatism is been proposed The extensive Permian/Triassic (P-Tr) extinction has been 8 R. B. Firestone

Table 2. Comparison of major igneous provinces dates and chronostratigraphic boundary dates.

Igneous Province Date Volume Reference Associated crater ages Age (Ma) Mkm3 (Ma) Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020 Viluy traps 370±8 >1 Ricci13 Devonian/Carboniferous 358.9±0.4 Emeishan traps 260.1±1.2 >1 Youjuan18 Capitanian/Wuchlapingian 259.1±0.5 Siberian traps 252.27±0.15 >3 Burgess15 Permian/Triassic 251.5±2.9 Central Atlantic Magmatic 205±1 0.7 Cheilletz10 Norian/Rheatian 208.5±2.0 Karoo and Farrar traps 179.2±1.8 1.5 Moulin11 Pliensbachian/Toarcian 182.7±0.7 Parana and Etendeka traps 134.5±0.5 21 Baksi18 Valanginian/Hauterivien 132.9±1.0 Ontong-Java plateau 1 121.7±2.7 44.4a Mahoney13 Barremian/Aptian 125±1 Rajmahal traps/Kerguelen plateau 117±4 6 Ray05 Aptian/Albian 113±1 Caribbean plateau 89±6 4.5 Dürke19 Coniacian/Turonian 89.8±0.3 Madagascar traps 87.8±1.4 4.4 Pande01 Coniacian/Turonian 89.8±0.3 Onton-Java plateau 2 83.7±3.1 a Mahoney13 Santonian/Campanian 83.6±0.2 Deccan traps 65.5±0.5 8.6 Fendley20 Cretaceous/Paleogene 66.0±0.5 North Atlantic Tertiary 60±3 2 Larsen16 Danian/Selandian 61.6±0.5 North Atlantic Tertiary 56±2 9.9 Larsen16 Thanetian/Ypresian 56.0±0.5 Ethiopian and Yemen traps 29±2 0.5 Riisager05 Eocene/Oligocene 27.82±0.20 Columbia River Flood Basalts 16.6±9.6 1.3 Cahoon20 Langhian/Burdigalian 15.97±0.20 a Total for both phases of Onton-Java plateau, primarily due to phase 1. linked to the Emeishan and Siberian traps Zhou et al.(2002), 252 Ma ago. Like the K-Pt extinction the P-Tr extinction occurred nearly instantaneously within an interval of 60±48 ka Burgess & Bowring (2015). The Emeishan traps are a relatively modest event and their date agrees poorly with the P-Tr extinction date. The amount of magma spewed by the Siberian traps is poorly known but could be as large as that from the Deccan traps. Only the 40 km Araguainha crater is accurately dated to that time, but the proposed Wilkes Land impact crater von Frese et al.(2009) in Antarctica, estimated to have occurred ≈260 Ma ago, is three times the size of the 150 km Chicxulub crater Klokocnik et al.(2018) which would be more than adequate to explain the P-Tr extinction. If confirmed the Wilkes Land impact should have caused the greatest extinction in history. The Triassic/Jurassic (Tr-J) extinction is often assumed to be due to the Central Atlantic Magmatic Province (CAMP) eruptions, 205 Ma ago, another modest volcanic event. The Tr-J ex- Figure 7. The percentage of species that have gone extinct are plotted versus tinction is described as a series of extinction events 201-205 Ma time Sepkoski et al.(2002) ago Wotzlaw et al.(2014), although the characterization of this as a . mass extinction rather than the result of normal evolutionary events has been questioned Lucas & Tanner(2018). No major impacts are known to have occurred during this time although we cannot rule Ma Ernst & Pisarevsky(2015). Most of these igneous events had out an unknown ocean impact. The Manicouagan crater in Canada no special environmental effect making any claims that they could is about half the size of Chicxulub crater and formed 13 Ma before cause a major extinction questionable. Volcanism is a continuous, the Tr-J extinction. An iridium layer from this impact is found in background process with igneous provinces being actively deposited Japan Onoue et al.(2012) suggesting that the ejecta layer spread over nearly all of Earth’s history. Although simple logic might con- globally. However, no evidence of extinction was found as far away vince us that volcanism is environmentally damaging it has been as Japan indicating that any associated extinctions would have been shown that at the P-Tr extinction "induced warming from volcanism closer to the impact site. The Manicouagan impact constrains the mitigated the most extreme effects of asteroid impact, potentially size of an impact necessary to cause a major extinction event. reducing the extinction severity" Chiarenza et al.(2020). Four of the five great extinctions can be explained by large impact events and the K-Pt impact provides strong evidence that 3.4 Comparison of impact crater ages with Marine these impacts can stimulate magmatism. Each extinction was nearly Extinction dates instantaneous and there is little evidence that magmatism could cause a sudden extinction. The high correlation between the for- The ocean marine extinction fossil records Napier(2015); mation of igneous provinces and the chronostratigraphic boundary Melott & Bambach(2010); Sepkoski et al.(2002) are shown in dates may be spurious if previous authors were biased to only look Fig.7 and the associated dates of the five major and three minor for a volcanic activity at specific times. Although the 16 selected extinctions are given in Table3. The marine dates are comparable igneous provinces are correlated with extinctions and chronostrati- to the boundary dates with a χ2/ f =0.93. 20 crater ages compare to graphicORIGINAL boundary dates, there are 41 igneous UNEDITED provinces of com- the marine extinction MANUSCRIPT dates with a χ2/ f =0.36 and to the chronos- parable size that are known to have existed during the past 440 tratigraphic dates with a χ2/ f =0.94. The difference in the quality Cosmic Impacts and Global Change 9

Table 3. Comparison of precise crater ages with marine extinction dates.

Timeline Boundary Boundary Marine Extinctions Associated crater ages Date (Ma) Date (Ma) % (Ma) Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020 Mid-Calabrian 1.8-0.774 1.1±0.7 8 Tenoumer Schultze et al.(2016) 1.57 ±0.14, New Quebec Grieve et al.(1991) 1.4 ±0.1 Eocene/Oligocene 33.9±0.5 35.4±1.5 16 Chesapeake Bay Assis Fernandes et al.(2019) 34.86 ±0.32, Popigai Wielicki et al.(2014) 33.9±1.3 Cretaceous/Paleogene 66.0±0.5 65.0±0.5 40 Chicxulub Schmieder & Kring(2020) 66.052 ±0.043, Boltysh Pickersgill(2019) 65.47±0.21 Jurassic/Cretaceous 145.0±1.0 143.7±1.8 20 Morokweng Beech et al.(2018) 145.0 ±0.8, Gosses Bluff Beech et al.(2018) 142.5 ±0.8 Triassic/Jurassic 201.3±0.2 200.2±0.6 43 Gow Lake Schmieder & Kring(2020) 196.8 ±9.9, Cloud Creek Stone & Therriault(2003) 190±20, Red Wing Grieve(1991) 200 ±5 Permian/Triassic 251.902±0.024 254.7±3.7 56 Araguainha Hauser et al.(2019) 251.5 ±2.9 Devonian/Carboniferous 358.9±0.4 ≈358.9 28 Woodleigh Beech et al.(2018) 364 ±8, Lockne Tillberg et al.(2019) 356.6 ±6.7 Frasnian/Farmennian 372.2±1.6 Ilyinets Beech et al.(2018) 378 ±5, Kaluga Beech et al.(2018) 380 ±5, 377.2±2.7 35 Frasnian/Givetian 382.7±1.6 Siljan Reimold et al.(2005) 377 ±2, Alamo Reimold et al.(2005) 382 ±4 Ordovician/Silurian 443.8±1.5 445.2±0.3 40 Calvin Schmieder & Kring(2020) 451 ±7, Pilot Bottomley et al.(1990) 445 ±2 of these fits is mainly due to the dates of the minor mid-Calabrian 3.5 Implications for the Pleistocene/Holocene boundary and the major Late Devonian extinction events. The Younger Dryas cooling occurred in less than a The mid-Calabrian marine extinction date has a very large year Wolbach et al.(2018a) and is coincident with the massive, uncertainty and could be interpreted as consistent with both the worldwide extinction of mammals weighing over 40 kg. It is es- Gelasian/Calabrian and the Calabrian/Chibanian boundary dates. timated that 73% of these animals disappeared in North Amer- ± The two crater ages give an average date of 1.46 0.08 Ma which is ica, 80% in South America, 94% in Australasia, 59% in Europe, inconsistent with all chronostratigraphic dates. This date is slightly 8% in Asia, and 14% in Africa. In addition to the extinction of earlier than the Mid-Pleistocene transition (MPT) in glacial cy- the megafauna in North America other species, including bison, ≈ cles Willeit et al.(2019); Ehlers et al.(2018) beginning 1.25 Ma deer, and moose suffered massive population losses Stuart(1991); ago. From 2.9-1.25 Ma ago there was a weak 41 ka glacial cy- Firestone(2019). Fossil evidence suggests that the disappearances cle which was followed by the more robust 100 ka Milankovich were very sudden. cycle Broecker et al.(1968). Many explanations have been given for the MPT including dust deposits in the Southern Ocean In a study of 97 geoarcheological sites Haynes(2008) found Hayward et al.(2007). Muller & MacDonald(1997) ascribed the that two thirds have a black, organic rich layer (black mat) that 100 ka glacial cycle to variations in the inclination of Earth’s or- dates to the onset of the YD. No evidence of megafaunal remains bital plane as it passes through the zodiacal cloud. Burchard(2018) is found within or above the black mat. He concluded that “strati- has suggested that the 100 ka glacial cycle at the MPT began with graphically and chronologically the extinction appears to have been a comet impact in the South China sea ejecting a belt of tektites catastrophic, seemingly too sudden and extensive for either hu- that the Earth encounters every 100 ka. Napier(2001) proposed man predation or climate change to have been the primary cause. that there is a 100 ka Jovi-Saturnian cycle that periodically moves The Younger Dryas impact layer is precisely dated to the onset of comets near Earth’s orbit. Although the MPT date does not coincide the Younger Dryas, exists only within the black mat, and consists with the crater ages, if it were due to an impact the first associated of PGE elements, spherules, nanodiamonds, aciniform carbon and ice age could begin up to 100 ka later when the Earth next passed other impact indicators observed at over two dozen sites on four con- through the debris cloud. The impact causing the MPT could have tinents Firestone et al.(2007); Wolbach et al.(2018a,b). Recently a occurred 1.35 Ma ago which is in better agreement with the crater 31-km diameter crater was found beneath the Greenland ice dating ages. to the late Pleistocene epoch Kjær et al.(2018); Klokočník et al. (2020). Since impacts of this size are correlated with the dates of The late Devonian period is characterized by a series of ex- previous epoch boundary dates it is possible that this impact was as- tinctions at 382.7-, 372.2-, and 358.9 Ma Carmichael et al.(2019). sociated with the Pleistocene/Holocene boundary date near the time The Devonian marine extinction is dated to 377.2±2.7 Ma Napier of the Younger Dryas 12.9 ka ago. Additional craters tentatively as- (2015) which is consistent with four craters whose average age is signed to this time are found in South Africa Thackeray et al.(2019) 379.8±2.4 Ma. This date lies in the middle of the Frasnian age and and in Canada Higgins et al.(2011). 20 Ma before the end of the Devonian period. The concordance The rapid cooling, deposition of an impact layer, and sudden of the marine extinction date and the crater ages suggests that the extinctions are all clear evidence that the onset of the Younger Dryas chronostratigraphic chart dates do not necessarily correspond to the was caused by a catastrophic event like a cosmic impact. It resembles actual catastrophe that triggered the Devonian extinction. the five previous global mass extinctions albeit not as large in scope. The average multiplicity of impact events associated with the It is consistent with the proposal that the giant comet 2P/Encke major marine extinction dates listed in Table3 is 2.1 which is broke apart 20-30 kyr ago, leaving the Taurus Complex asteroids in significantly higher than 1.7 multiplicity for the other impact events its debris field that are in an Earth-intersecting orbits Steel & Asher listed in Table1. Accounting for impacts that must have occurred (1996). It was proposed that major impacts would occur on a 103 − in the ocean this suggests that the average marine extinction was 104 year scale and is consistent with a cluster of impacts at the associated with 8-9 large impacts globally. This is consistent with onset of the Younger Dryas ending the Pleistocene epoch Napier theORIGINAL most prominent extinctions in Earth’s history UNEDITED being associated (2019b). Hoyle &MANUSCRIPT Wickramasinghe(2001) have suggested that such with the most intense periods of cosmic bombardment. large impacts could terminate ice ages in which case the cluster of 10 R. B. Firestone impacts ending the Pleistocene could have started as early as the Bølling-Allerød or even earlier Hagstrum et al.(2017) and may not yet have ended. The Tunguska impact in Siberia in 1908 is proposed to be a cometary fragment from the Taurid complex Asher & Steel Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020 (1998). Rohde & Muller(2005) have reported a 62 ±3 Ma frequency of major marine extinction events, the last of which occurred 65.0±0.5 Ma ago. This cycle may be due to the sun’s passage into and out of the galactic plane and its spiral arms during its orbit of the galaxy Rampino(1997). It suggests that a major extinction event could be due now. Not all dates in the 62 Ma cycle were associated with major extinctions. The extinction at Jurassic/Cretacious boundary, 145±1 Ma ago, affected mainly the largest dinosaurs and marine life Tennant(2017), as seen in Fig.7, and is coincident with the large Morokweng crater age. The Carniverous Rainforest collapse at ≈305 Ma Sahney et al.(2010) occurred near the time of an expected mass extinction but appears to be caused by cli- Figure 8. Holocene craters, (•), airbursts (X), cold periods (--), and cold pe- mate change with no evidence of major impacts at that time. The riods accompanied by tsunamis (--). The airbursts are plotted at an arbitrary Younger Dryas extinctions are comparable to the lesser events in vertical position. the 62 Ma extinction cycle albeit without significant marine extinctions. However, at the end of the Pliocene, 2.58 Ma ago, 36% of marine megafauna (mammals, seabirds, turtles and sharks) became extinct Pimiento et al.(2017). This extinction occurred at the time of the Eltanin impact in the South Pacific ocean that produced a 60 m high tsunami 6,000 km away and would have had a crater up to 60 km in diameter Ward & Asphaug(2002). The YD and Eltanin impacts fall within the time window of the next expected mass extinction event although with less severity than the major mass extinctions. The many gaps in the 62 Ma cycle make this correlation tenuous.

3.6 The Holocene and beyond The impact rate has increased significantly as Earth passes through the center of the local bubble. At the same time the chronological ages have become progressively shorter. The Holocene epoch is assumed to begin at the end of the Younger Dryas 11.7 ka ago. It is divided into three chronological ages, the Greenlan- dian ending 8.2 ka ago, the Northgrippian ending 4.2 ka ago, and the Meghalayan continuing to modern times. Each boundary date corresponds to the onset of a cooling period except Figure 9. Decrease in the global temperature anomaly with respect to the for the Pleistocene/Holocene boundary which is assigned to the average temperature Rohde & Hausfather(2020) following the Tunguska end of the Younger Dryas cooling period. Six little ice ages or and more recent airbursts. Only the smallest Curuçá River airburst was not cold periods occurred 291 Derham(1708), ≈565 Büntgen et al. followed by a short global cooling spell. (2016), ≈3600 Seifert & Lemke(2015a), ≈4200 Yan & Liu(2019), ≈7500 Seifert & Lemke(2015b) and ≈8200 Kobashi et al.(2007) years ago. The impacts and airbursts are all correlated with subsequent cooling 19 craters or crater clusters and 11 & 100 kT airbursts are periods. known to have occurred during the Holocene. In addition, 3 ocean The Greenlandian/Northgrippian and Northgrip- impacts have been identified by the occurrence of impact ejecta in pian/Meghalayan boundary dates are concordant with both coastline chevron dunes formed by tsunamis Abbott et al.(2010b); tsunamis and 27-30 km crater ages. Airbursts in Ch’ing-yang, Gusiakov et al.(2009). They are listed in Table4 and plotted in Spain, and the Dead Sea caused many human casualties and Fig.8. Remarkably nearly all of the craters listed are the largest widespread damage. The Tunguska impact flattened 80 million member of a cluster of several nearby craters. All of the crater, air- trees over an area of 2000 km2. The smaller Chelyabinsk impact burst, and chevron ages are closely associated with the boundaries caused damage over a 500 km2 area and injured 1200 peo- dates and ice ages giving a χ2/ f =0.75. As described above the ex- ple Popova et al.(2013). As shown in Fig.9 the Tunguska airburst perimental data were compared to a Monte Carlo simulation where caused up to > 1◦C global cooling for nearly a year and the recent 200 randomly selected crater age datasets with dates ranging from smaller airbursts, releasing an energy of >100 kT, caused up to 0.3-4.2 ka and assuming 15% uncertainties were generated. Com- > 1◦C cooling for several days. parison with the boundary and ice age dates gave χ2/ f values rang- At least five significant airbursts have occurred during the past ingORIGINAL from 0.62-4.0 with only two simulations UNEDITED having χ2/ f <0.73. 1500 years suggesting MANUSCRIPT a frequency of <300 years comparable to The likelihood that the experimental correlations is random is ≈1%. predictions Toon et al.(1997) but contrary to NASA impact hazard Cosmic Impacts and Global Change 11

Table 4. Holocene craters, airbursts, and meteors. The craters and meteors are plotted at an arbitrary vertical position.

Impact Age Y(BP) Width (km) or Comments Reference Airburst Energy (kT) Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020 Kamchatka 2 173 Russia, Airburst, December 18,2018 Luo et al.(2020) Chelyabinsk 7 500 Russia, Airburst, February 15, 2013 Borovička et al.(2013) Prince Edward Islands 57 266±90 Indian Ocean, Airburst, August 3, 1963 Edwards et al.(2006) Arroyomolinos de León 88 190 Spain, Airburst, December 8, 1932 Madiedo & Trigo-Rodríguez(2011) Curuçá River, 90 100 Brazil, Airburst, August 13, 1930 de La Reza et al.(2004) Tunguska 112 15,000 Russia, Airburst, June 30, 1908 Gasperini et al.(2007) Sobolev 275±25 0.053 Russia, Crater Schmieder & Kring(2020) Wabar 290±38 0.09 Saudi Arabia, 5 crater cluster Prescott et al.(2004) Chiemgau 500±200 15 Germany, 80 crater cluster Ernstson et al.(2010) Mahuika 550±50 20 New Zealand, Marine crater Abbott et al.(2005) Tappan 572±86 12 Australia, crater Abbott et al.(2010a) Kanmare 572±86 18 Australia, crater Abbott et al.(2010a) Iberian Peninsula 939 Spain, Airburst, June 1, 939 Llorca et al.(2009) St Michael’s Day 1006±67 Britain and Wales, Tsunami, September 28, 1014 Abbott et al.(2010b) Chinese meteors 1030±50 Airburst, Historical record Hasegawa(1992) Chinese meteors 1430±10 Airburst, Historical record Hasegawa(1992) Ch’ing-yang 1490 China, Airburst, February/March 1490 Yau et al.(1994) Sirente 1540±100 0.127 Italy, 17 crater cluster Ormö et al.(2006) Kaali 3460±50 0.107 Estonia, 9 crater cluster Losiak et al.(2016) Middle Ghor 3700±50 Dead Sea, Airburst Silvia(2017) Campo del Cielo 3995±85 0.103 Argentina, 27 crater cluster Cassidy & Renard(1996) Morasko 4000±1000 0.1 Poland, 8 crater cluster Stankowski et al.(2002) Burckle 4550±250 29 Indian Ocean, Chevron associated with tsunami Abbott et al.(2010a) Henbury 4200±1900 0.18 Australia, 13 crater cluster Storzer & Wagner(1977) Boxhole 5400±1500 0.17 Australia, may be part of Henbury cluster Shoemaker et al.(2005) Ilumetsa 7135±85 0.077 Estonia, 2 crater cluster Losiak et al.(2020) Macha 7380±80 0.3 Russia, 5 crater cluster Gurov & Gurova(1998) Tibet 7600±600 27 Southern Tibet, 11 crater cluster Patil(2018); Rades et al.(2013) Deluge 8200±250 30 Norway, Storrega slide, tsunami Bondevik et al.(2012); Bryant(2008) YD impact 12830±25 Impact layer, four continents Wolbach et al.(2018a) Hiawatha >11700 31.1 Greenland, Crater Kjær et al.(2018); Klokočník et al.(2020) Wonderkrater 12700±1100 ≈5 South Africa, Crater Thackeray et al.(2019) Corossol ≈12900 4 Canada, Crater Higgins et al.(2011) prediction of a 1000 year frequency Morrison et al.(1994). Five ka Past and Interglacials and Working and Group and of and PAGES impact related tsunamis have been recorded in the past 8200 years (2016). Although the next ice age might be due soon, global warm- suggesting a frequency of 1600 years compared to the impact haz- ing is expected to extend the current interglacial. The recent ards prediction of 63,000 years. Nearly all of the recent craters airbursts and impacts are all coincident with cooling episodes so it occurred in clusters, conventionally assumed to be due to scattered is possible that a future impact could reverse global warming or impact material Robbins & Hynek(2014). Clusters of craters are even propel Earth into another ice age. An ice age would be an even rare in the crater database and Ivanov et al.(2008) have shown that greater peril to human survival than global warming as human only ≈35% of craters on Mars are in clusters from impacts of low populations plummeted during the last ice age Posth et al.(2016). density objects. Similarly Wheeler & Mathias(2019) have shown that Tunguska-like airbursts also favor low density objects. This is consistent with nearly all recent impacts being due to fragile, low density comet meteoroids Matlovič et al.(2017) some of which ex- plode as airbursts and others that shatter at the ground. The airbursts 4 CONCLUSIONS will cause an order of magnitude more blast damage than surface A strong correlation was found between the stratigraphic boundary impacts. dates and the ages of impacts. After correction for expected impacts The likelihood that an airburst could devastate an area the size into the oceans and ice sheets there were likely at least 700 major of Tokyo is 33% over the next 100 years. Four impacts produced impacts during the entire chronostratigraphic record. The five major 12-20 km craters and one produced a large tsunami during the past extinction events occurred suddenly, as seen in the marine extinction 1000 years suggesting that there is a 40% chance of a similar event data, and are coincident with the largest known impact events. There capable of devastating an area the size of Great Britain in the next is a clear association in both the timing and severity of sudden century. Three impacts that produced 27-30 km craters, capable of geological change with cosmic impact events. damaging an area the size of India occurred during the past 8000 Volcanism, also correlated with major extinction events, is years suggesting that a similar event has a 4% chance of occurring shown to be an intense and continuous process over Earth’s history during the next 100 years. with little correlation between magmatic production rates and global ORIGINALInterglacials have a duration ofUNEDITED 10-30 ka and environmental change.MANUSCRIPT Evidence suggests that large impacts may Earth has been in the current interglacial for ≈15 even induce volcanism although no evidence exists that an increase 12 R. B. Firestone in volcanic activity could cause the sudden extinctions that are Bond D. P., Wignall P. B., 2014, in , Volcanism, Impacts, and observed. Mass Extinctions: Causes and Effects. Geological Society of Amer- A likely cause of clusters of impacts is passing stars, interstellar ica, doi:10.1130/2014.2505(02), https://doi.org/10.1130/2014. objects, and γ-rays from near Earth supernovae that disrupt the 2505(02) Downloaded from https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staa3790/6041705 by Flinders University user on 19 December 2020 Oort Cloud sending comets into the inner solar system where they Bondevik S., Stormo S. K., Skjerdal G., 2012, Quaternary Science Reviews, 45, 1 would break up into debris clouds that intersect with Earth’s orbit. Borovička J., Spurný P., Brown P., Wiegert P., Kalenda P., Clark D., Shrbený Interstellar comets, common in the galactic arms, will also break L., 2013, Nature, 503 up in the inner solar system. This process is consistent with the Bottke W. F., Richardson D. C., Love S. G., 1997, Icarus, 126, 470 increased impact rate observed as Earth is passing through the OB Bottomley R. J., York D., Grieve R. A. F., 1990, Lunar and Planetary Science star association where nearby supernovae and interstellar objects Conference Proceedings, 20, 421 are common. An impact ended the Pliocene epoch bringing on the Broecker W. S., Thurber D. L., Goddard J., Ku T.-L., Matthews R., Mesolella Pleistocene epoch that ended in a cluster of impacts at the onset K. J., 1968, Science, 159, 297 of the Younger Dryas. These impacts are coincident with major Bryant E., 2008, Comets and asteroids. Springer Berlin Heidelberg, extinctions events on both land and sea. It is proposed that these Berlin, Heidelberg, pp 231–269, doi:10.1007/978-3-540-74274-6_8, events are the latest instance of the 62 Ma extinction cycle. https://doi.org/10.1007/978-3-540-74274-6_8 There is likely that a powerful airburst or impact will occur Burchard H., 2018, Open Journal of Geology, 08, 1 Burgess S. D., Bowring S. A., 2015, Science Advances, 1 in the next century. This event is be expected to cause a period Carmichael S. K., Waters J. 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