Prehistoric Astronomy and the Younger Dryas Catastrophe?

[Michael B-C]

Thanks Itellsya for pointing out the implications of Pierre’s article regarding the most likely date/cause of the change in earth’s axis. And the gravity anomalies around Hudson Bay highlighted by mariowil7 are also very interesting.

Assuming that it happened in relatively recent human history (and many of the most ancient myths speaking about a previous golden age and a single season certainly are suggestive of that), it makes most sense that the catastrophic events of some 13,000 years ago have to be a prime culprit. Anything later really doesn’t align with so much else especially the development of seasonal stories, the slow emergence of agriculture/civilisation and many of the myths that followed. A close passage or interaction with ‘Venus’ and ‘Mars’ are perhaps the only other recent suspects – placing when that happened and how these events are related to the end of the ice age event is still a question for me… were they as seems likely later follow on events…? Was ‘Venus’ one of the large broken pieces of the original monster or a new interloper? Did she take on repeated close passages as a result of the disturbances caused to the inner solar system by the 13,000 year event before eventually either wearing herself out or settling into a plentary orbit as propossed by Velikovsky?… placing these in something like a correct order is a monumental tease…

The issue of the impact on zodiacal lore is one of key significance however. If we assume the earth was wholly or more upright and that most if not all of the present 23degree tilt only came about post the catastrophic end of the ice age, then any theory that deduces an extrapolation of current ecliptic/zodiacal constellations as being meaningfully consistent back in time beyond this point is in trouble as obviously it is only this tilt that creates the ecliptic and places the constellations we know along its sight line. Without it the zodiac would be on or under the horizon and have no reason to have impacted human consciousness. It also raises the issue of whether the Precession of the Equinoxes also only dates post this time.

This is where I have some issues with Sweatman’s “Prehistory Decoded". I was uncomfortable with many of his almost cavalier deductions concerning the imagery on the T stones at Gobekli Tepe and his firm connections to current zodiacal constellations. Having studied Sumerian and Babylonian astronomy in some detail it is clear that as late as between 5-1,000 BC constellations were constantly changing, evolving and even being written off in large numbers and new ones created in their stead particularly as a result of the effects of precession. Revision of the sky over long periods of time must be taken into account it seems to me and it’s a huge leap to claim that constellations that we know today had similar or comparable meaning, imagery or place in the lore of the ancients over such huge time spans.

As an example, in his fantastically informative and important book BABYLONIAN STAR-LORE, Gavin White posits the following with regard to the erasing of a whole tranche of once pivotal constellations that I wonder may possibly have something very important to say with regard to the fabled 11 strong zodiac of old…

P82

THE CREATURES TIAMAT

The Creatures of Tiamat are a group of 11 mythical beings found in the Epic of Creation. They are of considerable interest to astrologers because four of them appear in star-lists as constellations in their own right. In this respect, they bear many similarities to another group of mythical beings known as the Heroes’, a number of which embody memories of archaic constellation figures that were removed from the heavens in ages long past.

Along with a host of venomous serpents and ferocious dragons, the 11 Creatures were created by Tiamat to fight against the gods. Tiamat was an ancient goddess, the embodiment of the primeval oceans, who held sway among men before the arrival of the gods. In the ensuing battle Marduk killed Tiamat, routed her battle-legions and captured her monstrous host.

After the victorious Marduk had bound and imprisoned the Creatures, he set about constructing a new world-order from the corpses of his slain adversaries. He divided Tiamat’s dead body into two halves from which he created heaven and earth. He then sacrificed Kingu, Tiamat’s battle-leader and lover, and from his spilt blood he created ‘primeval’ man’, the blood of the slain god constituted the ghost of that first man.

However, Marduk was more lenient towards the 11 Creatures, after binding them and making them subservient to him, he made images of them and installed them at the gate of the Abyss to commemorate his victory. Ultimately, the purpose of Marduk’s leniency towards the Creatures was to harness their power for benevolent ends. Thus they became ‘protective entities’, whose allotted role was to guard the entranceways to temples, palaces and houses. So, in addition to affirming Marduk’s supremacy over all creation, the magical function of the Creatures was henceforth to protect buildings against the incursions of other demons and monsters.

The names and natures of the 11 creatures are as follows:

The Furious Serpent (mušhuššu) is first seen in the artwork of the Akkadian period. It is a composite creature made up from the parts of a serpent, lion and bird. During its long history it has been associated with various gods, first with Ninazu and Tišpak, later with Ningišzida, Marduk and Aššur. It appears as a constellation in the Old Babylonian ‘Prayer to the Gods of the Night’ (see fig 121).

The Bašmu-serpent is regarded as an early name for the constellation later known as the Serpent. In later artwork the Bašmu is depicted as a horned serpent with two front legs and wings (see fig 120). Its name can be understood as the ‘horned serpent with a womb’.

The Exalted Serpent (mušmahhu) is sometimes thought to be the same as the seven-headed serpent slain by Ninurta. In early artwork just such a beast is attacked by a hero who slices off one of its heads (see fig 40). The motif has ultimately inspired the Greek myth of Heracles’ labour against the seven-headed dragon called the Hydra.

The Great Dragon (ušumgallu) might be the 4-legged dragon with wings that appears in some late 3rd millennium artwork. In truth, the attribution is uncertain, as the Great Dragon is often confused with the bašmu-serpent whose name is also derived from Ušum, the Sumerian term for ‘dragon’. The term ‘Great Dragon’ can be used as an epithet of deities and kings where it means ‘the sovereign’ or ‘sole ruler’.

The Lahāmu appears to be a collective term for a group of watery beings, half-man, half-fish in appearance. According to creation myths they are primeval beings born from the waters of Tiamat. In later traditions they could be found in the subterranean waters among the entourage of the wise god Enki. Together with Enki they guard the ‘bolt of the sea’ that seems to be related to the abundance of the oceans.

The Great Storm-demon (Ugallu) is a lion-headed demon that first appears in Akkadian art; by the Old Babylonian period he is associated with the gods of the underworld where he is considered to be a punisher of transgressors and a bringer of disease. Armed with a mace and an upraised dagger, his appearance is to all intents and purposes identical to the lion-headed demon known as Lulal. (see figs 86 & 88)

The Mad Dog (Uridimmu) is a relatively rare figure that is first attested in Kassite art. The Mad Dog, has a human head and torso set upon a lion’s hindquarters. This precise form is generally considered to be a late invention based on similar composite figures like the Bison-man and Scorpion-man. In later artwork it is often paired with the Bison-man as an attendant to the sun god Šamaš. The Mad Dog appears among the constellations next to the Scorpion, it is ultimately the origin of the Greek constellation known as the Wolf (Lupus). (see figs 12 & 90)

The Scorpion-man (Girtablilu) first appears in Akkadian art where it is depicted with a human head, bird’s legs, a snake-headed penis and a scorpion’s segmented body and tail, in addition some examples also sport wings. From the Kassite period a slightly different figure appears that has the body of a bird and which is sometimes armed with a bow and arrow, but it is uncertain whether this particular creature can also be called a ‘scorpion-man’. In the artwork of later periods Scorpion-men commonly appear alongside the sun god and the winged disk. (see figs 97& 117)

The Fierce Storm-demon (Ūma dabrutu) is probably a composite beast that incorporates the features of a lion, but beyond this its appearance is uncertain. It is sometimes thought that a lion-like creature with the back legs of a bird is an ūma-demon. Such creatures first appear in Akkadian art and are essentially identical to the depiction of the Panther-constellation. The similarity is reflected in later star- lore where the Panther is sometimes glossed as ūmu nā’iru - the ‘roaring’ or ‘snarling storm-demon’. Such a creature, with water flowing from its mouth, is occasionally portrayed as the sacred beast of various storm gods. (see fig 102)

The Fish-man (Kulilu) and Fish-woman first appear in the artwork of the Old Babylonian period, where they often appear in pairs wearing the horned headdresses of divinity. They are naturally associated with the water god Enki and are counted among the wise inhabitants that dwell in the watery Abyss below the earth. (see fig 5 & 6)

The Bison-man (Kusarikku) is a mythical beast derived from the bison. He is generally depicted with a human head and torso, and the hindquarters of a bison. He is closely associated with the sun god Šamaš in the Akkadian and Old Babylonian periods; and is listed as a constellation in the Old Babylonian ‘Prayer to the Gods of the Night’.

(see figs 10-13)



p193

THE SLAIN HEROES

The Slain Heroes are a fascinating group of ‘primitive’ gods, demons and monsters that were all killed by the heroic god Ninurta. There is mounting evidence that several of the Heroes were actually worshiped as independent divinities as early as the Early Dynastic period (3100-2390 BCE). Their ‘deaths’ at the hands of Ninurta had certainly occurred by the end of the 3rd millennium as the Gudea inscriptions attest to their collective worship within the cult of Ninqirsu (a local form of Ninurta) around 2100 BCE.

The defeat of the Heroes is widely thought to represent a attempt to absorb their independent worship into the cult of Ninurta, and may be but a part of a much wider cultic and religious reform that took place in the mid to late 3rd millennium. The most persuasive evidence for this cultic upheaval can be found in Akkadian artwork, where brutal scenes depicting the slaughter of captive gods abound.

In appendix 2, l have argued that the origins of this ‘war of the gods’ lies in a substantial reform of the constellations where numerous archaic constellation figures were removed from the star-map to be replaced by newly formed star- figures.



127 A warrior god, possibly Ninurta, slays a one-eyed solar deity, Old Babylonian plaque



In the present state of knowledge, we can only be certain that two of the Slain Heroes - the Anzu-bird and the Bison-man - were indeed ancient constellation figures that were struck from the heavens, but there is the distinct possibility that several more Heroes were also archaic constellation figures. In fact the Slain Heroes may not be as ‘dead’ as their names imply - as there is reason to believe that some of them may actually live on in some Greek constellations. I have noted the potential correspondences below.

It is now widely recognised that the myths of the Slain Heroes have inspired at least some of the Greek myths known as the Labours of Hercules. There are some particularly convincing parallels between Hercules’ Labours against the Hydra and the Boar of Erymanthia, and their Mesopotamian prototypes known as the Seven-headed Serpent and the Bison-man. This intriguing topic deserves further investigation.

Most mythic texts mention nine heroes, who seem to form some kind of canonical group, however other texts add at least two more Heroes to their number. Their names and natures, as far as can be discerned, are as follows:

The Six-headed wild ram (Šeg9-Sag-6) was slain by Ninurta who ‘brought it forth from the shining, lofty house’. Gudea later installed the ram at the ‘gate of battle, where the weapons hang’.

The Warrior Dragon (Ušum Ur-sag) was ‘brought forth from the great fortress of the mountains’. The Warrior Dragon was sometimes considered to be the counsellor of Tišpak, a warrior god who had a number of serpentine beings among his divine entourage. (See the section on the Star of Dignity).

The Magilum boat is possibly a boat with a human head or torso that is seen in early artwork. Ninurta ‘brought it forth from ... hi Abyss’. Some modern researchers have suggested that the Magilum boat may be remembered in the Greek constellation of Argo. The evidence in favour of such an attribution is limited and largely depends on some Arabic illustrations of the Argo, which depict it as a ship with human characteristics.

The Bison-man (Gud-Alim) was ‘brought forth from Ninurta’s battle dust’. His constellation is partly remembered in the Greek Centaurus, but in mainstream Babylonian tradition his constellation was removed from the heavens and replaced by the figure of the Wild Boar. (See the section on the Bison-man and figs 10-14)

The Mermaid (Kulianna) was ‘brought forth from the limits of heaven and earth’. In the section on Anunitum, I suggest that a memory of Kulianna may be retained on the Greek star-map in the form of Andromeda. (See fig 6)

The White Gypsum (Nig-Babbar-ra) was brought forth from the soil of the mountain range’.

The Strong Copper (Urud-nig2 Kalag-ga) was ‘brought forth from the shattered mountain range’. He appears in the Sumerian poem entitled ‘the debate between Copper and Silver, where he is said to be the ‘strong heir of Father Enlil’. Some commentators have suggested that Strong Copper was a personified bell, used in later periods in exorcistic rituals.

The Anzu-bird (lm-Dugud-mušen) was a lion-headed eagle well known in archaic myth and art. Ninurta ‘brought it forth from the halub-haran tree’ (a form of oak). The Anzu-bird’s constellation image was once located in the region around Pegasus, but was subsequently replaced by the Horse constellation A memory of the Anzu-bird may be retained in the Greek star-map in the form of Cygnus, the Swan, whose outstretched wings and trailing feet bear an uncanny resemblance to depictions of Anzu. (See the section on the Anzu-bird and figs 7-8)

The Seven-headed serpent (Muš-Sag-7 or Mušmahhu) is sometimes seen in early artwork, where it is attacked by a warrior god (See fig 40). Ninurta ‘brought it forth from the ... of the mountains’.

Among the lesser-known Heroes we also find Lord Samanana, whose name, according to the lexicon, would mean the ‘Lord of the cosmic tethering rope’. A deity of this name was worshipped in the Early Dynastic period, and in Old Babylonian incantations a monstrous demon called Samana is sometimes mentioned. The little known Palm-tree king was also worshipped in the Early Dynastic period. And one of the Gudea inscriptions also seems to imply that the ‘Lion, terror of the gods’ was included among the Slain Heroes.

The Slain Heroes may not be as dead as the Babylonian sources suggest as some of their number could actually be incorporated into the Greek star-map. The most certain case is that of the Bison-man who lives on, albeit in a modified form, under the Greek name Centaurus. As mentioned above a memory of the Magilum boat may inform the celestial ship called the Argo; and it is also possible that the form of Cygnus, the Greek Swan, is a slightly displaced and modified version of the Anzu-bird.

Beyond the star-map there could be further inherited memories of the Heroes in the corpus of Greek mythology. The most obvious example is the Seven-headed Serpent, which is, no doubt, the precursor of the Greek Hydra. For now the matter needs to be left unresolved - we can only hope that future discoveries concerning the Heroes will throw more light on this intriguing issue.

Taking the above into account, plus all the wealth of detail concerning the ever evolving star-scape above (a simple example being the evolution of a fascinating figure called The Hired Man into the Ram of Aries that took place quite late on) – and even though there are real symbolic connections between the two, the iconography and indeed the actual shape of the constellation was significantly altered. We should also bring to mind the pivotal halving of what was once the full constellation/iconography of Tauraus the Bull to in part facilitate this.

Sweatman makes the classic and to my mind fatal mistake that so many have made before in falsely assuming that associated constellational lore/imagery and the actual shape of the stars in the sky are in anyway connected. They are not, and even in the few cases where this can be argued, it is obvious this was not the defining reason why certain areas of the sky were chosen to assume certain imagery around which important knowledge could be located and retained. The heavens were the ancients super computer. The sky above was their sacred metaphysical/physical text. We are not talking about bored, sub-civilised thinkers who stared up at the heavens and in their spare time undertook a children’s game of join the dots (‘Hey, that looks just like a lion!”) but rather the projection of an incredibly subtle, complex, interwoven memory system – a kind of giant cosmic library of multi-levelled knowledge written upon the heavens and maintained orally over over millennia through which high initiates and priestly astronomer astrologers (it is never the common people who come up with these processes and myths) maintained, lost and remade through countless catastrophes and collapses of human culture, a timeless yet ever evolving understanding of the above and the below in perpetual union and strife. And whilst I wholeheartedly agree with Laura that later Greek and neo-platonic ‘esoteric’ extrapolations and interpretations were falsely attached with garbled meaning, that from the get go the system had an inherent ‘spiritual’ aspect hand in hand with the harsh reality aspect derived from constant threats from the heavens by ‘the gods’ in the form of comets and where they ‘lived’. When you begin to trace the evolution of the sky story you constantly come across startling and clear associations to a double and concurrent underlying story – one of human spiritual potential, entrapment and the means to escape side by side and interlocked with the realities of our 3rd density matrix and its 4th density control system. I think the true lost story is one of a slow erasing of this complex understanding and a replacement with one more fractured and obtuse – very much in alignment with what happened when writing replaced oral capacity allowing for a process of Chinese whispers to occur that the Bible and its makers used to ensure the past was near washed clean.

Anyhow, Sweatmans interpretation of ‘Pattern Matching’ of such figures as The Fox, Tall Bending Bird, Duck/Goose, Bending Bird, etc to current known constellations is to my mind a huge leap in assumptions and whilst his statistical arguments impressive, should – to my mind – not easily be accepted on face value.

However I do accept that his overall argument is most likely absolutely in the right direction – and whilst my jury is open I think his deducing that the 4 ‘handbags’ are markers of the equinoxes and solstices has merit and is worth further exploration – especially if these 4 sign posts were new and freshly important signifiers of something hugely significant post the initial catastrophe and the establishment of the 4 seasons.

 

[Michael B-C]

As an addendum to the above, here's Gavin White's attempt at recreating the star map of circa 5,000BC. He openly admits its a work in progress but its certainly suggestive of a cross over happening between a previous landscape and the one we have now.

 

[Altair]

he issue of the impact on zodiacal lore is one of key significance however. If we assume the earth was wholly or more upright and that most if not all of the present 23degree tilt only came about post the catastrophic end of the ice age, then any theory that deduces an extrapolation of current ecliptic/zodiacal constellations as being meaningfully consistent back in time beyond this point is in trouble as obviously it is only this tilt that creates the ecliptic and places the constellations we know along its sight line. Without it the zodiac would be on or under the horizon and have no reason to have impacted human consciousness. It also raises the issue of whether the Precession of the Equinoxes also only dates post this time.

Without this 23° tilt the ecliptical plane would be simply coplanar with Earth's equatorial plane so tilt doesn't create ecliptic. It means that zodiac would simply consist partly or completely of different constellations. And due to different visible size of constellations, I can imagine, that in the "pre-tilt" zodiac some (probably the smaller ones) constellations would be "replaced" by others while others (the bigger ones) would "remain" and that zodiac itself would possibly even consist of a bigger or smaller number of constellations.

From Wiki:

The ecliptic is the mean plane of the apparent path in the Earth's sky that the Sun follows over the course of one year; it is the basis of the ecliptic coordinate system. This plane of reference is coplanar with Earth's orbit around the Sun (and hence the Sun's apparent path around Earth).[1] The ecliptic is not normally noticeable from Earth's surface because the planet's rotation carries the observer through the daily cycles of sunrise and sunset, which obscure the Sun's apparent motion against the background of stars during the year.

The zodiac is an area of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic, the apparent path of the Sun across the celestial sphere over the course of the year.

The Earth in its orbit around the Sun causes the Sun to appear on the celestial sphere moving along the ecliptic (red), which is tilted 23.44° with respect to the celestial equator (blue-white).

Added: I'm pretty sure that it would be relatively easy to calculate which constellations zodiac would consist of if the Earth rotational axis wasn't tilted.

 

[Michael B-C]

Without this 23° tilt the ecliptical plane would be simply coplanar with Earth's equatorial plane so tilt doesn't create ecliptic. It means that zodiac would simply consist partly or completely of different constellations. And due to different visible size of constellations, I can imagine, that in the "pre-tilt" zodiac some (probably the smaller ones) constellations would be "replaced" by others while others (the bigger ones) would "remain" and that zodiac itself would possibly even consist of a bigger or smaller number of constellations.

Hi Altair. Yes indeed, thank you; excuse my rather cack-handed description of the effects of the tilt re ecliptic and zodiac. But I think it does still mean that in particular the northern hemisphere sky from the equator up would have had a markedly different look to today, with as you say the zodiac consisting partly or completely of different constellations. That was my main line of thought regarding its implications when extrapolating the zodiac of today back to the symbols at Gobekli Tepe.

 

[Altair]

Hi Altair. Yes indeed, thank you; excuse my rather cack-handed description of the effects of the tilt re ecliptic and zodiac. But I think it does still mean that in particular the northern hemisphere sky from the equator up would have had a markedly different look to today, with as you say the zodiac consisting partly or completely of different constellations. That was my main line of thought regarding its implications when extrapolating the zodiac of today back to the symbols at Gobekli Tepe.

Yes, it would be different. Would be interesting to find out to what extent it would differ.

Added: without this tilt there would be no seasons and no equinoxes and possibly no reason for the people on Earth to create zodiac.

 

[mrtn]

Without the tilt the sun would still travel through the same stars in the sky as seen from earth, because it is the axis of earths rotation that is tilted, not the orbit of the earth. Alignment from earth to sun to the stars behind doesn't change. Over the year the position of the sun and stars in the sky wouldn't wobble in a wave fashion. The sun at noon would (seen from one place on earth) be the same height from the horizon in December and June or any other month. On the north pole it would be shadow permanently and you would see the same stars the whole year (the latter is the case now as well, just with a different pole star). A bit further south on earth the sun would travel constantly on the horizon, never rising or setting other than caused by land features. But still the stars behind the sun would be the same as they are now in a particular season. What a year is would be measurable only by the sun-stars relation, when the stars (moving parallel to the horizon) behind the sun have traveled 360° and the sun is in the same sign again. But note that sun and stars travel parallel to the horizon only over the course of the year, but seen from a certain point on earth they would still rise and set during over the course of a day.

As for the canceled text above, I think that was wrong. If you go south and come out of the pole shadow then the sun would just rise very slightly for a moment in the day, but would also travel deeper below the horizon at night, when your position on earth is on the nightside facing outer space away from the sun.

Does that make sense?

 

[Altair]

Another piece of evidence for Younger Dryas Impact Hypothesis. The paper attached.

The Younger Dryas interval at Wonderkrater (South Africa) in the context of a platinum anomaly
J.F. Thackeray, L. Scott & P. Pieterse

Received 1 March 2019. Accepted 23 August 2019

Abstract

Wonderkrater in the Limpopo Province in South Africa is a late Quaternary archaeological site with peat deposits extending back more than 30 000 years before the present. Palaeoclimatic indices based on multivariate analysis of pollen spectra reflect a decline in tempera- ture identifiable with the Younger Dryas (YD). A prominent spike in platinum is documented in a Wonderkrater sample (5614) with a mean date of 12 744 cal yr BP using a Bayesian model, preceding the onset of the YD cooling event. The YD platinum spike at Wonderkrater is the first to be observed in Africa in the southern hemisphere, supplementing new discoveries from Patagonia in South America, in addition to more than 25 sites with such platinum anomalies in the northern hemisphere. The observations from South Africa serve to strengthen ongoing assessments of the controversial YD Impact Hypothesis, whereby it is proposed that a meteorite or cometary impact contributed to a decline in temperature, associated inter alia with dispersion of atmospheric dust, mammalian extinctions and cultural changes.

[...]


Figure 1. Map showing the location of Wonderkrater in South Africa, in relation to more than 25 other Younger Dryas (YD) sites which also have anomalies in platinum concentrations (orange dots) in deposits dated at circa 12 800 cal yr BP. Red dots represent sites with other YD impact proxies including spherules, as well as nanodiamonds as reported for example by Kurbatov et al. (2010). The Pilauco site in Patagonia (southern Chile) and Wonderkrater are as yet the only known sites in the southern hemisphere where YD platinum spikes have been reported. Map drawn after Pino et al. (2019). North and Central America map source: USGS, Sioux Falls; Japan ASTER Program (2003), ASTER Global Digital Elevation Map, GDEM-10 km-BW, from ASTER Global Digital Elevation Map, 10.5067/ASTER/ASTGTM.002.

DISCUSSION AND CONCLUSIONS

The platinum spike in sample 5614 at Wonderkrater precedes the onset of the Younger Dryas cooling event (Fig. 2a,b). Since strong evidence for spikes in platinum has been obtained for the YD interval from more than 25 sites in Europe, Asia and North America (e.g. Kennett et al. 2009, 2015; Petaev 2013; Moore et al. 2017) as well as Mexico (Israde-Alcantara 2012) and Patagonia (Pino et al. 2019),
and now also at Wonderkrater in the southern hemi- sphere (Fig. 1), the Younger Dryas Impact Hypothesis is in part supported, recognizing criticisms expressed by Pinter et al. (2011), Holliday et al. (2014) and others. One criticism (Tankersley et al. 2018) is that volcanic activity can be a source of platinum (apart from cosmic impacts), but no volcanic activity has been documented in southern Africa within the late Quaternary.

The YD Impact Hypothesis expresses the view that Terminal Pleistocene extinctions can be attributed to a cosmic impact. Without invoking any one particular causal factor, we note the occurrence of terminal Pleisto- cene extinctions of fauna such as Equus capensis, Syncerus antiquus, Megalotragus priscus and Antidorcas bondi in South Africa (Klein 1972 1978; Faith 2011, 2012, 2013a,b, 2014; Thackeray 1980). However, a YD impact cannot account as an instantaneous causal factor since Megalo- tragus (for example) persists in the interior of the country at Wonderwerk (probably at low population densities) until about 7500 BP (Thackeray 2015).
Megafaunal extinctions in South Africa may be attrib- uted to both environmental change and human predation within a period of time before and after 12 800 cal yr BP.

However, on the basis of data presented in this study, it may be cautiously considered that the consequences of a hypothesized YD cosmic impact (and the dispersion of atmospheric dust) may have contributed to some extent to the process of extinctions not only in southern Africa, but also to that which occurred in North and South America as well as Europe, recognizing synchroneity of Pt anomalies (Kennett et al. 2015) that has been cited in support the Younger Dryas Impact Hypothesis.

We note that in terms of culture, the apparently abrupt change from Robberg to Oakhurst technocomplexes in South Africa as documented, for example, at Boomplaas Cave in the southern Cape (H.J. Deacon 1979 1995; J. Deacon 1982 1984), penecontemporary with the Younger Dryas, is closely co-incident with the cultural change from Clovis to Folsom technologies in North America. The question as to whether this relates indirectly if not directly to a common causal YD cosmic impact is beyond the scope of this article which serves primarily to report a YD plati- num anomaly in the Wonderkrater sequence.

Apart from Wonderkrater, the Younger Dryas cooling interval has been detected from the analysis of pollen in hyrax middens (Chase et al. 2011, 2013, 2015, 2018) and also from oxygen isotope records from terrestrial Achatina snails at Bushman Rock Shelter (Abell & Plug 2000) and marine mollusc shells from Elands Bay (Cohen et al. 1992). Notably, the cultural change between Robberg and the Oakhurst techno-complexes at the former site occurs at about the time of the YD (Mitchell 1988; Lombard et al. 2012 ; Porraz et al. 2015).

The suggestion that the hypothesized YD impact is related in particular to the Hiawatha crater in northern Greenland remains to be conclusively determined on the basis of absolute dates. However, it can already be noted that the large crater rim (31 km in diameter) has not been subject to substantial erosion, and glacial ice older than 12 800 BP is missing (Kjær et al. 2018). Irrespective of where an impact might have occurred, the YD Impact Hypothe- sis is supported in part by this study of the Wonderkrater Core 3 sequence in South Africa in which a platinum spike is reported for sample #5614, with a mean date of 12 744 cal yr BP using Scott’s (2016) Bayesian model, preceding the onset of the YD cooling event.

This is the first evidence in Africa to partially support the YD Impact Hypothesis on the basis of a platinum anomaly in a late Quaternary sedimentary sequence. The Pilauco site in Patagonia in southern Chile (Pino et al. 2019) and Wonderkrater are as yet the only known sites in the southern hemisphere where YD platinum spikes have been reported, supplementing the corresponding evidence from more than 25 sites in the northern hemisphere, dated circa 12 800 cal yr BP.

 

[Carl]

New research supports hypothesis that asteroid contributed to mass extinction

A team of scientists from South Africa has discovered evidence partially supporting a hypothesis that Earth was struck by a meteorite or asteroid 12 800 years ago, leading to global consequences including climate change, and contributing to the extinction of many species of large animals at the...

phys.org

A team of scientists from South Africa has discovered evidence partially supporting a hypothesis that Earth was struck by a meteorite or asteroid 12 800 years ago, leading to global consequences including climate change, and contributing to the extinction of many species of large animals at the time of an episode called the Younger Dryas.

The team, led by Professor Francis Thackeray of the Evolutionary Studies Institute at the University of the Witwatersrand in Johannesburg, South Africa, discovered evidence of a remarkable "platinum spike" at a site called Wonderkrater in the Limpopo Province, north of Pretoria in South Africa.

.............

A large crater 31 kilometers in diameter has been discovered in northern Greenland beneath the Hiawatha Glacier. "There is some evidence to support the view that it might possibly have been the very place where a large meteorite struck the planet earth 12 800 years ago," says Thackeray. "If this was indeed the case, there must have been global consequences."

Thackeray's team believes their discovery of a platinum spike at about 12 800 years ago at Wonderkrater is just part of the strengthening view that an asteroid or cometary impact might have occurred at that time.

This is the first evidence in Africa for a platinum spike preceding climate change. Younger Dryas spikes in platinum have also been found in Greenland, Eurasia, North America, Mexico and recently also at Pilauco in Chile. Wonderkrater is the 30th site in the world for such evidence.

"Our evidence is entirely consistent with the Younger Dryas Impact Hypothesis" says Thackeray.

The probability of a large asteroid striking Earth in the future may seem to be low, but there are thousands of large rocks distributed primarily between Jupiter and Mars. One in particular, classified as Apophis 99942, is referred to as a "Potentially Hazardous Asteroid." It is 340 meters wide and will come exceptionally close to the Earth in 10 years' time.

"The closest encounter will take place precisely on Friday April 13, 2029," says Thackeray. "The probability of the Apophis 99942 asteroid hitting us then is only one in 100 000, but the probability of an impact may be even higher at some time in the future, as it comes close to Earth every 10 years."

Are people actually waking up to this? I can't help but postulate that the increasing widespread appeal of the YD Impact Hypothesis in this timeline is due in large part to Laura's efforts many years ago.

Also I'm starting to see an uncanny number of little "data points" pointing at the date range of 2025-2030 as the place where things could get really really "interesting".

 

[Vulcan59]

The American Geophysical Union now supports Younger Dryas event.

Abstract
The Younger Dryas (YD) abrupt cooling event (~12,900 yr to 11,600 yr) represents a brief return to severe cold conditions in mid- to high- latitudes in the Northern Hemisphere. The cooling is thought to have resulted from freshwater flooding of the northeast Atlantic and/or the Arctic Oceans that prevented deep water formation and promoted extensive southward expansion of sea-ice. Two different triggers that would lead to freshwater capping the north Atlantic have been proposed: (1) catastrophic drainage of proglacial Lake Agassiz and (2) a meteorite impact-related partial destabilization and/or melting of the Laurentide ice sheet. However, the physical evidence for these triggers remains elusive. Recent revision in the age of Laacher See volcano (Volcanic Explosivity Index = 6) in Eifel, Germany has led to the suggestion that the YD event was triggered by emplacement in the stratosphere of large amounts volcanic sulfur and halogens with sustained cooling resulting from a positive feedback involving sea ice expansion and/or AMOC shutdown. Thus, building of sea-ice rather than freshwater capping provides a trigger according to this hypothesis. Here, we use GRIP ice core to investigate whether the YD was engendered by a one-time catastrophic event or whether it was an integral part of a sequence of events that unfolded as the last ice-age came to a close. We sampled GRIP ice core every 9 cm from a depth of 1659.35 m to 1664.30 m corresponding to a time-resolution of 2-3 years spanning 12,939-12,810 yr b2k. Decontaminated ice-core was analyzed for δ18O, δD, major cations and anions, trace-elements, and osmium and lead isotopes. We find that a massive volcanic eruption occurred at 12,918 yr b2k and that immediately following the eruption the d-excess increases from 4 to 9 permil over a period of 37 years indicating a profound increase in sea-ice. During this time period, ratio of fluxes mantle to continental derived osmium also increases. Additionally, there is evidence of a 20-fold increase in extra-terrestrial osmium flux ~12,819 yr b2k following which the δ18O values display a steep and sustained decline to –40 permil. These signals suggest that volcanism potentially induced the YD cooling, which may have been further exacerbated by an extra-terrestrial impact.

 

[Pierre]

The American Geophysical Union now supports Younger Dryas event.
[...]
These signals suggest that volcanism potentially induced the YD cooling, which may have been further exacerbated by an extra-terrestrial impact.

That's the least mainstream science could concede knowing the overwhelming evidence of cometary impacts ca. 12,800 BP.

However their statement is still misleading. I don't think that volcanism induced cooling was worsened by an extraterrestrial impact but rather that multiple extraterrestrial impacts induced the YD cooling and triggered volcanic eruptions too.

The thing is, recent history of our planet is marked by numerous ice core dust spikes that are systematically attributed to volcanic eruptions.
Problem is, for most spikes there's no eruption with matching date!

The diagram above shows SO2 (sufur dioxide) concentrations in GISP2 (Greenland) ice core over the past 16,000 years :

It shows 62 spikes that reach more than 120 ppm. Some of the spikes reach 800 ppm. For comparison, the "giant" Krakatoa eruption generated about 150 ppm of sulfur.

Out of those 62 major spikes, only 14 are tentatively associated to a volcanic eruption. The two largest ones (-10,657 BC and -9,285 BC) have no associated eruption whatsoever.

It raises an obvious question: "how many ice core dust spikes are wrongly attributed to volcanic eruptions while being the result of cometary events (direct impact or overhead explosion)?"

 

[thorbiorn]

It shows 62 spikes that reach more than 120 ppm. Some of the spikes reach 800 ppm. For comparison, the "giant" Krakatoa eruption generated about 150 ppm of sulfur.

Out of those 62 major spikes, only 14 are tentatively associated to a volcanic eruption. The two largest ones (-10,657 BC and -9,285 BC) have no associated eruption whatsoever.

To go from 150ppm for Krakatoa to 800 ppm sounds like a lot, but Krakatoa is really far away from Greenland being just south of the equator. Would it have made a difference if it had been closer? At least the distribution is not always uniform. Below are two pictures showing the situation near an erupting volcano and near a smelter, but the question is at what altitude the concentrations were found, and if some of the sulfur would be removed by precipitation in the form of snow, rain or hail?

https://www.researchgate.net/publication/253011406_Enhanced_monitoring_of_sulfur_dioxide_sources_with_hyperspectral_UV_sensors

More on sulfur emissions from volcanoes and earth quakes
On Stratospheric sulfur aerosols - Wikipedia there is:

Sulfur aerosols are common in the troposphere as a result of pollution with sulfur dioxide from burning coal, and from natural processes. Volcanos are a major source of particles in the stratosphere as the force of the volcanic eruption propels sulfur-containing gases into the stratosphere. The relative influence of volcanoes on the Junge layer varies considerably according to the number and size of eruptions in any given time period, and also of quantities of sulfur compounds released. Only stratovolcanoes containing primarily felsic magmas [Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium.]are responsible for these fluxes, as mafic magma [Mafic is an adjective describing a silicate mineral or igneous rock that is rich in magnesium and iron, and is thus a portmanteau of magnesium and ferric.[1]] erupted in shield volcanoes doesn't result in plumes which reach the stratosphere.

Creating stratospheric sulfur aerosols deliberately is a proposed geoengineering technique which offers a possible solution to some of the problems caused by global warming. However, this will not be without side effects[2] and it has been suggested that the cure may be worse than the disease.[3]

Stratospheric sulfur aerosols - WikipediaWhat is useful about this information is that volcanic origin would involve a stratovolcano, and rather than one big stratovolcano what if a few smaller ones went off at the same time? From the distinction between felsic and mafic lava one might be led to the idea that not all volcanoes release equally much sulfur. There was an article from 2018's biggest volcanic eruption of sulfur dioxide which mentioned that:

2018's biggest volcanic eruption of sulfur dioxide
Date:February 28, 2019Source:NASA/Goddard Space Flight CenterSummary: The Manaro Voui volcano on the island of Ambae in the nation of Vanuatu in the South Pacific Ocean made the 2018 record books. A NASA-NOAA satellite confirmed Manaro Voui had the largest eruption of sulfur dioxide that year.

The Manaro Voui volcano on the island of Ambae in the nation of Vanuatu in the South Pacific Ocean made the 2018 record books. A NASA-NOAA satellite confirmed Manaro Voui had the largest eruption of sulfur dioxide that year.

The volcano injected 400,000 tons of sulfur dioxide into the upper troposphere and stratosphere during its most active phase in July, and a total of 600,000 tons in 2018. That's three times the amount released from all combined worldwide eruptions in 2017.

During a series of eruptions at Ambae in 2018, volcanic ash also blackened the sky, buried crops and destroyed homes, and acid rain turned the rainwater, the island's main source of drinking water, cloudy and "metallic, like sour lemon juice," said New Zealand volcanologist Brad Scott. Over the course of the year, the island's entire population of 11,000 was forced to evacuate.

At the Ambae volcano's peak eruption in July, measurements showed the results of a powerful burst of energy that pushed gas and ash to the upper part of the troposphere and into the stratosphere, at an altitude of 10.5 miles. Sulfur dioxide is short-lived in the atmosphere, but once it penetrates into the stratosphere, where it combines with water vapor to convert to sulfuric acid aerosols, it can last much longer -- for weeks, months or even years, depending on the altitude and latitude of injection, said Simon Carn, professor of volcanology at Michigan Tech.

In extreme cases, like the 1991 eruption of Mount Pinatubo in the Philippines, these tiny aerosol particles can scatter so much sunlight that they cool the Earth's surface below.

The map above shows stratospheric sulfur dioxide concentrations on July 28, 2018, as detected by OMPS on the Suomi-NPP satellite. Ambae (also known as Aoba) was near the peak of its sulfur emissions at the time. For perspective, emissions from

Hawaii's Kilauea and the Sierra Negra volcano in the Galapagos are shown on the same day. The plot below shows the July-August spike in emissions from Ambae.

"With the Kilauea and Galapagos eruptions, you had continuous emissions of sulfur dioxide over time, but the Ambae eruption was more explosive," said Simon Carn, professor of volcanology at Michigan Tech. "You can see a giant pulse in late July, and then it disperses."

The OMPS nadir mapper instruments on the Suomi-NPP and NOAA-20 satellites contain hyperspectral ultraviolet sensors, which map volcanic clouds and measure sulfur dioxide emissions by observing reflected sunlight. Sulfur dioxide (SO2) and other gases like ozone each have their own spectral absorption signature, their unique fingerprint. OMPS measures these signatures, which are then converted, using complicated algorithms, into the number of SO2 gas molecules in an atmospheric column.

"Once we know the SO2 amount, we put it on a map and monitor where that cloud moves," said Nickolay Krotkov, a research scientist at NASA Goddard's Atmospheric Chemistry and Dynamics Laboratory.
These maps, which are produced within three hours of the satellite's overpass, are used at volcanic ash advisory centers to predict the movement of volcanic clouds and reroute aircraft, when needed.

Mount Pinatubo's violent eruption injected about 15 million tons of sulfur dioxide into the stratosphere. The resulting sulfuric acid aerosols remained in the stratosphere for about two years, and cooled the Earth's surface by a range of 1 to 2 degrees Fahrenheit.

This Ambae eruption was too small to cause any such cooling. "We think to have a measurable climate impact, the eruption needs to produce at least 5 to 10 million tons of SO2," Carn said.

Still, scientists are trying to understand the collective impact of volcanoes like Ambae and others on the climate. Stratospheric aerosols and other volcanic gases emitted by volcanoes like Ambae can alter the delicate balance of the chemical composition of the stratosphere. And while none of the smaller eruptions have had measurable climate effects on their own, they may collectively impact the climate by sustaining the stratospheric aerosol layer.

"Without these eruptions, the stratospheric layer would be much, much smaller," Krotkov said.

Earthquakes can also lead to the outgassing of sulfur: Outgassing of hydrogen sulfide and other gases off Kaikoura Peninsula, New Zealand -- Sott.net

Sulfur coming from the impact of meteorites
The above idea of more sulfur being present in felsic magma led to the idea that stony meteorites may contain more sulfur than iron meteorites, but the Wikis had little to say about sulfur in stony meteorites: Chondrite - Wikipedia or iron meteorites: Iron meteorite - Wikipedia
There was one paper claiming the content of sulfur in chondrites is much much higher than in the other elements they tested selenium and tellurium, but those being rare this is not a surprise: https://www.researchgate.net/public...abundances_in_chondrites_and_their_components

More interesting is the following:

<Impact-induced perturbations of atmospheric sulfur>

When an asteroid or comet impacts a planetary body, it releases a tremendous amount of energy. Except for objects smaller than a few meters, the impacting asteroid or comet is obliterated by the energy of the impact. The impactor material is mixed with the target material (the rock on the planet's surface) and dispersed in the form of vapor, melt, and rock fragments.

During the impact, sulfur in the impactor or in sulfur-containing target rocks can be injected into the atmosphere in a vapor-rich impact plume. In some impact events, such as Chicxulub, the rocks hit by the impactor contain sulfur. Sedimentary rocks hit by an impactor sometimes include large amounts of evaporites. Evaporites are rocks that are formed with minerals that precipitated from evaporating water, such as halite (rock salt) and calcite (calcium carbonate). Two other very common evaporite minerals are gypsum (CaSO4 + H20) and anhydrite (CaSO4), both of which contain sulfur (S).

Projectiles also contain sulfur-bearing minerals, particularly the mineral troilite (FeS), which is obliterated in an impact event. This material releases its sulfur, which is then injected into the stratosphere. The amount of sulfur injected into the stratosphere depends partly on the composition of the projectile, which can vary from one crater to another. Using chemical traces of the projectiles left at impact craters, scientists can determine the type of meteoritic material involved. Using this data, scientists can then calculate the amount of sulfur each specific impact injects into the stratosphere. The amount of this sulfur can be substantial, because meteoritic materials contain up to 6.25 weight percent sulfur. Consequently, even if the asteroid or comet does not hit a S-rich target, it can still cause dramatic increases in the total amount of atmospheric sulfur.

Once vaporized, this sulfur can react with water to form sulfate (or sulfuric acid) particles. These particles can greatly reduce the amount of sunlight that penetrates to the surface of the earth for a period of up to several years. Over time, the sulfate will settle out of the stratosphere (upper atmosphere) into the troposphere (lower atmosphere) where they can form acid rain which can have additional environmental and biological effects.

There was probably an impact on Greenland about 10,000 BC but might that have led to a spike in the content of sulfur? Hiawatha Glacier - Wikipedia

To sum up the above possible ideas of where to look for an explanation for the spikes of sulfur found in the Greenlandic ice cores they could be related to one or more stratovolcanoes or earthquakes leading to a release of sulfur, but some volcanoes release much more sulfur than others. A spike in sulfur could be a result of a large impact releasing sulfur contained in the material of the impactor and or released from the impacted rock.

 

[Pierre]

To sum up the above possible ideas of where to look for an explanation for the spikes of sulfur found in the Greenlandic ice cores they could be related to one or more stratovolcanoes or earthquakes leading to a release of sulfur, but some volcanoes release much more sulfur than others. A spike in sulfur could be a result of a large impact releasing sulfur contained in the material of the impactor and or released from the impacted rock.

A lot can be said about the confusion between volcanic eruptions vs. cometary events regarding dust spikes found in ice cores (and more generally catastrophes). I address this topic in an article that was published today: "Volcanoes, Earthquakes And The 3,600 Year Comet Cycle"

 

[thorbiorn]

A lot can be said about the confusion between volcanic eruptions vs. cometary events regarding dust spikes found in ice cores (and more generally catastrophes). I address this topic in an article that was published today: "Volcanoes, Earthquakes And The 3,600 Year Comet Cycle"

Thank you for the latest article linking the Younger Dryas event to a few other comet events.
The article mentions the Hiawatha crater in Greenland, I tried to look up some more information about this impact and found from 2018 a paper with the title: A large impact crater beneath Hiawatha Glacier in northwest Greenland
[ Also as pdf on https://advances.sciencemag.org/content/advances/4/11/eaar8173.full.pdf ]
The article mentions the geology of the place, but to get a better understanding I looked up other sources. The article also explains what the impact event could have looked like, by far the most interesting part. Still, I will begin with the geology, because if there was ejecta from this impact then they ought to reflect some of the local compositions of the rocks around the crater.

The geology in the area of Greenland where the Hiawatha crater is located.
A large impact crater beneath Hiawatha Glacier in northwest Greenland mentions:

The composition of ice-marginal erratic boulders derived from beneath Hiawatha Glacier indicates that the identified structure was formed within the same types of highly metamorphosed Paleoproterozoic terrain as mapped across most of Inglefield Land, which is part of the east-west–trending Inglefield mobile belt (fig. S1)

More details of the geology of the Inglefield Land can be found on page 12-23 in this document: https://eng.geus.dk/media/12967/map1_p01-48.pdf While there is marble in the area, it is more common a little away from the Hiawatha area, where the crater was found. In the Hiawatha area there appears to be more granite like rocks, at least on the surface. While I looked into this, I wondered what would happen if marble got heated by an impact. Marble is CaCO3 and it it was heated to 840 degrees Celcius, it would release the CO2 and become CaO. CaO has a molar mass af about 57 g/mole while CaCO3 has a molar mass of just above 100 g/mole. This would mean that for every ton of superheated marble one would have 430 kg of CO2.
There is more on the geology in this abstract, and there one learns there may be sulfur rich deposits in the region: https://www.researchgate.net/public...orthwest_Greenland_A_new_mineralisation_style has:

Inglefield Land in northwest Greenland is an ice-free 7000 km² region underlain by the Palaeoproterozoic Inglefield mobile belt, composed of quartzo-feldspathic gneisses, meta-igneous and supracrustal rocks. These rocks are unconformably overlain by an unmetamorphosed cover of sedimentary and igneous rocks of the Mesoproterozoic Thule Basin and the Lower Palaeozoic Franklinian Basin. Mineralisation in Inglefield Land is characterised by a copper–gold metal association that can be classified in terms of the hosting rocks, namely: garnet–sillimanite paragneiss-hosted, orthogneiss-hosted and mafic–ultramafic-hosted. The paragneiss-hosted mineralisation, the topic of this paper, is essentially confined within a NE-trending structural corridor and consists of bands of sulphide±graphite-bearing, hydrothermally altered, quartzo-feldspathic gneiss, called “rust zones”. These are commonly parallel to the paragneiss main foliation, suggesting a close relationship. The rust zones have strike lengths from a few metres to more than 5 km, and widths ranging from a few centimetres to 200 m. Sulphides mainly include pyrrhotite, pyrite and chalcopyrite. The sulphides form disseminations, up to 30% by volume, but in places they form massive pods or lenses up to 20–30 m, and about 0.1–0.5 m wide. Graphite contents are up to 5 vol.%. Rust zones typically consist of a quartz–plagioclase mosaic associated with a late generation of red-brown biotite, sericite, chlorite and epidote. Mylonitic or cataclastic textures are locally recognisable. XRD analyses of graphite indicate temperatures of between 650 and 700 °C. Sulphur isotope analyses show δ³⁴S values ranging from −6.2‰ to +9.3‰

And one last sources about the geology of the area is: Alba Mineral Resources Plc (AIM:ALBA) Further exploration ground secured at Inglefield which mentions:

· GEUS has identified that Inglefield Land has the potential for copper-zinc volcanogenic massive sulphide (VMS) deposits, which are associated with and created by volcanic-associated hydrothermal events in submarine environments

· Previous extensive surface sampling has reported anomalous copper (up to 1.39%), gold (up to 1.7g/t), cobalt (up to 0.16%), vanadium and nickel

· High grade float reported to have been collected in West Inglefield historically, returning 8.8% cobalt and 7.6% nickel, showing the significant potential of the region

Next to the more interesting part about the creation of the crater In A large impact crater beneath Hiawatha Glacier in northwest Greenland they mention that they did not find any ejecta that they could yet correlate with what ought to be there if it had come from the Hiawatha area.

Preliminary estimates of impactor and ejecta properties. The diameter of an impact crater constrains the kinetic energy of the impactor. The formation of a 31-km-wide impact crater in crystalline target rock requires ~3 × 10^21 J of energy (17). Assuming that the Hiawatha impactor was iron with a density of 8000 kg m−3 and its impact velocity was 20 km s−1, the required impactor diameter was ~1.5 km (17). The impact would initially produce a bowl-shaped cavity ~20 km in diameter and ~7 km deep, which would quickly collapse (within~1min) to form a complex crater more than 31 km in diameter and ~800m deep with a central uplift (17). This impact scenario would have melted and vaporized up to ~20 km3 of target rock, approximately half of which would have remained within the crater, forming a melt sheet up to ~50 m deep.

No ejecta layer that might be associated with the Hiawatha impact crater has yet been identified in either Greenland’s rock or ice records. If no ice was present at the time of a high-angle (>45°) impact, then the
symmetric ejecta layer would be ~200 m thick at the rim, thinning to less than 20m at a radial distance of 30 km from the rim (17). However, during most of the Pleistocene, an ice sheet covered the impact area
(18). If ice was present and its thickness was comparable to the impactor’s diameter, then a more energetic projectile is required to produce a crater of the observed size, and the fraction of non-ice debris in the ejecta would be smaller than if the impact hit ice-free land (19). Furthermore, regionally extensive ice cover at the time of impact could have resulted in a significant fraction of the ejecta landing on the ice-sheet surface of the Greenland or Innuitian ice sheets, rather than on bare ground. As the crater is situated very close to the present ice margin, the site has almost certainly been ice free during one or several short
(~15 ka) interglacial periods during the Pleistocene, such as predicted for the Eemian ~125 ka ago (20).On the basis of present ice-flow speeds (Fig. 1B), most impact ejecta deposited onto the ice sheet would have
been transported to the ice margin within ~10 ka. Similarly, based on Holocene vertical strain rates (21), any such ejecta would be less than half of its original thickness within 10 ka.

If the Greenland Ice Sheet was present at the time of impact and a high-angle impact occurred during the late Pleistocene (LGP), then ejecta ought to be present in the four deep ice cores from central and northern Greenland that span the majority of the LGP (fig. S5), but none has yet been identified. At two of the ice cores (GISP2 and GRIP) located farthest (>1000 km) from the crater (fig. S5), the expected initial thickness of a symmetric ejecta layer for a Hiawatha-sized impact on rock is ~0.7 mm with an average particle diameter of ~0.4 mm (17). In the closer ice cores (fig. S5), this thickness increases roughly twofold. If ice were present at the impact site, then a significant fraction of the ejecta would also be ice (19), but the presence of any rock ejecta should be unambiguous in an ice core. A possible complicating factor to interpreting the absence of ejecta in ice cores south of the structure is the presently unknown angle of impact. Modeling indicates that oblique impacts (<45°) produce asymmetric ejecta predominantly downrange of the crater with an ejecta-free shadow zone up range and that this effect becomes more pronounced as the impact angle decreases (22). The Hiawatha impact crater is located farther north (78.72°N) than any other known impact crater, a position that increases the probability of a northward-directed oblique impact given the majority of Earth-crossing asteroids that move in or near the ecliptic plane. Such a scenario might be analogous to the late-Jurassic Mjølnir crater,which is also large (40 km diameter), is high latitude (73.8°N), and produced an asymmetric (northward focused) ejecta layer (23).

Because it is not yet known whether the Greenland Ice Sheet covered this region at the time of the impact, or its thickness at that time or the impact angle, our estimates of impactor size, initial crater size, impact melt volume, and ejecta thickness and extent should be considered preliminary.

Age of the Hiawatha impact crater
[...]
Radar evidence of active basal melting (full-column radiostratigraphic synclines) and subglacial water storage (groundwater table) within and beneath Hiawatha Glacier, respectively, appear to be anomalous as compared to grounded ice-marginal settings across northern Greenland. Possible basal melting could be due to an anomalous subglacial heat source and is consistent with, but not conclusive of, residual heat from the impact itself. Previous modeling of hydrothermal systems within martian subaerial impact craters suggests that such systems have a life span of ~100 ka for a 30-km-wide crater (31). For the terrestrial Hiawatha impact crater, the overlying ice sheet would have provided an ample supply of water for such a hydrothermal system during the Pleistocene and Holocene, but it would have also exported heat more efficiently from that system than for a subaerial crater, which suggests a shorter life span of any possible post-impact hydrothermal system than on Mars.

Apparently the

It may be that the impactor making the Hiawatha crater did not leave as many traces in the icecore, as one might expect due to the angle of impact and other factors,.All that is still to be settled, but reading this paper was a minor shock for me. Imagine a ball of iron with a diameter of 1.5 km moving at more than 70,000 km per hour making a 20 km wide and 7 km deep hole in the earth within fractions of a second which then all collapses within about a minute leaving a 31 km crater that is only 800 meters deep. but still the residual heat from the impact would be expected to linger on for thousands of years - in one of the coldest places on the planet. That is scary, don't you think?

On this page there are some illustrations of the crater: SVS: The Hiawatha Impact Crater like:

A still image showing a comparison of the size of the Hiawatha crater to Washington, DC.

A still image showing a comparison of the size between the Hiawatha crater and Paris, France. The region shown is limited by the Paris super-périphérique (A86) ring road around the city.

This image shows another view of some radar data from the airborne survey of the Hiawatha crater displayed on opaque curtains. A blue bar indicates the height of one kilometer. The blue arrow points to one of the central peaks.

 

[Pierre]

Imagine a ball of iron with a diameter of 1.5 km moving at more than 70,000 km per hour making a 20 km wide and 7 km deep hole in the earth within fractions of a second which then all collapses within about a minute leaving a 31 km crater that is only 800 meters deep. but still the residual heat from the impact would be expected to linger on for thousands of years - in one of the coldest places on the planet. That is scary, don't you think?

Quite scary indeed. It makes the whole "global warming" hysteria all the more derisory where activists freak out about an hypothetical 0.2°C warming over the next 10 years.

The Hiawata crater also shows how little is known and how little is invested to discover, understand and properly date impact craters. How many unfound craters are on Earth's surface? How many craters have been barely investigated? How many craters don't have a proper dating?

The same could be said for ice cores, for which crucial markers like platinum, iridium, mercury, nanodiamonds... are rarely investigated (apart for the 12800 BP event that is now recognized as a cometary impact).

I think if impact craters and ice cores were thoroughly investigated, it would clearly appear that cometary events (impacts and/or overhead explosion and/or electric interactions) are way more frequent and destructive than currently believed.

Actually, after perusing this topic for a while, I've come to the idea that cometary events might well be the greatest modulator of life on Earth in general, and the rise and fall of civilizations in particular.

 

[Jacques]

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