Apocalypse, Cataclysm & Mega-Disaster - Past and Future

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TenEightyOne

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Here we go with a zombie apocalypse story. Continental readers will recall the BSE apocalypse in '80s and '90s affecting Britain and Europe that cost billions to deal with.


"Zombie deer disease,” a mad cow-like infection spreading in the US, explained
A mad cow-like infectious disease that can turn the brains of deer, elk, and moose into “Swiss cheese.”
By Julia Belluz@juliaoftorontojulia.belluz@voxmedia.com Feb 21, 2019, 9:50am ESTSHARE
GettyImages_911536146.0.jpg



As of January 2019, 251 counties in 24 states had reported chronic wasting disease in free-ranging deer, the CDC reported. You can see them here:

Screen_Shot_2019_02_20_at_10.26.03_AM.png

Chronic wasting disease in free-ranging deer, reported by US county, as of January 2019.
CDC



https://www.vox.com/2019/2/21/18233227/zombie-deer-disease-map

How related is this disease to BSE and are there likely to be human case of CJD (or similar) from it? If so there needs to be a quickly-enforced ban on game going into the human food chain until a national, workable response is organised. The scale is incredible though.
 

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How related is this disease to BSE and are there likely to be human case of CJD (or similar) from it?
This is helpful: https://wwwnc.cdc.gov/eid/article/10/6/03-1082_article

Apparently the direct risk to humans is low, but it is the same as BSE - the big danger to humans would be if CWD spread to livestock/cattle and caused a new BSE outbreak, which in turn would pose a health risk to humans.
 

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I have seen reports of raccoons and coyotes infected with the wasting disease infiltrating human neighborhoods.
 

Dennisch

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How related is this disease to BSE and are there likely to be human case of CJD (or similar) from it? If so there needs to be a quickly-enforced ban on game going into the human food chain until a national, workable response is organised. The scale is incredible though.


Now, now, no need to rush things. Let's see how this plays out. Perhaps this is the start of an actual zombie apocalypse. My machete is ready.
 

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12,900 years ago a mass extinction event wiped out most of the large and all of the very large mammals on the the North American continent, around 30 species. The sophisticated Stone Age civilization known as Clovis also disappeared. A layer in the Earth, the Black Mat, is associated with this event. Iridium and hexagonal nano-diamonds are found in increased abundance, as they are in the same time layer in Greenland ice cores. This indicates a cosmic event occurred. But no obvious crater has been found, though the hypothesized impactor could have broken up into smaller bodies before striking earth - or the mile-deep Laurentide Ice Sheet. Scientists are still puzzled. Follow the hunt and the clues in the excellent video below.

 

TenEightyOne

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The sophisticated Stone Age civilization known as Clovis also disappeared.

The mass extinction event that wiped out most of the Earth's remaining Clovis was the white settlement of North America. Around 75% of surviving native tribes have Clovis DNA.
 

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Paleontologists note that Clovis paleoIndian campsites in North America suddenly terminate at one point and LaViolette notes that this Clovis end date either immediately preceded or coincided with the date of the 12,837 years BP super SPE.

Although a new paleoIndian civilization resurfaced some centuries later, these new findings raise the question as to whether this super SPE may have been the cause of the disappearance of the Clovis civilization.

http://www.spacedaily.com/reports/Did_A_Massive_Solar_Proton_Event_Fry_The_Earth_999.html
 

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What do magnetic and glassy impact-related spherules, nanodiamonds, carbon spherules, biomass burning, and anomalous levels of platinum and chromium in Younger Dryas sediment layers all have in common? We have suggested the view that it was a solar outburst, or recurrent micro-nova. Some evidence suggests that impact (actually airburst) events may be to blame.


New Study Finds Evidence for Younger Dryas Impact Hypothesis in Chile

Micah HanksMarch 25, 2019

What do magnetic and glassy impact-related spherules, nanodiamonds, carbon spherules, biomass burning, and anomalous levels of platinum and chromium in ancient sediment layers all have in common?

Here’s a hint: it involves a controversial theory about an ancient cataclysmic event… and one that is gaining new support, after an international team of scientists found compelling new evidence for its cause in South America.

The Younger Dryas impact hypothesis contends that around 12,800 years ago, a disintegrating comet or asteroid led to an impact event—or maybe several—along with possible airbursts which resulted in widespread fires and climate changes identified in relation to the Younger Dryas Climate Event.

Proponents of the theory also believe climate changes occurring at this time may have been a contributing factor in megafaunal extinctions, along with existing evidence of human predation, which began to occur several thousands of years ago. However, archaeological evidence also seems to indicate that human populations were affected at the same time; presumably a result of the same environmental changes.


Evidence for large scale climate changes related to these proposed impacts or air bursts had been found already on several continents. However, a new study titled “Sedimentary record from Patagonia, southern Chile supports cosmic-impact triggering of biomass burning, climate change, and megafaunal extinctions at 12.8 ka,” argues that features remarkably similar to existing North American sites associated with the Younger Dryas Boundary (YDB) were found at the South American archaeological and paleontological site of Pilauco Bajo.

According to the new paper’s extract:


“In the most extensive investigation south of the equator, we report on a ~12,800-year-old sequence at Pilauco, Chile (~40°S), that exhibits peak YD boundary concentrations of platinum, gold, high-temperature iron- and chromium-rich spherules, and native iron particles rarely found in nature.”

As I noted elsewhere in relation to the new Chilean discoveries, “The significance of the platinum concentrations and other metallic signatures at the Chilean site presents another unique identifier, with relevance to previous studies that located an anomalous abundance of the rare earth metal at several YDB sites, as well as within ice core samples from the Greenland Ice Sheet. Christopher R. Moore, Ph.D. of the South Carolina Institute of Archaeology and Anthropology, University of South Carolina, Columbia, who contributed to the recent Chilean study, was the lead author of a paper published in Scientific Reports in 2017 which first identified this platinum anomaly.”

UC Santa Barbara geology professor emeritus James Kennett, also a co-author on the new paper, says at least one of the discoveries made at Pilauco, Chile, was unique to the site. Kennett was particularly interested in an abundance of chromium found in the YD boundary at the new location, since it is an element that is not commonly found at similar sites located in the Northern Hemisphere.

However, Kennett told UC Santa Barbara’s The Current that “volcanic rocks in the southern Andes can be rich in chromium,” which he and other scientists conducting research on the site felt could explain the prevalence of the material.

“Thus, the cometary objects must have hit South America as well,” Kennett concludes. The paper appeared on March 13 in Scientific Reports and can be viewed online here.

The Younger Dryas impact hypothesis remains controversial, largely due to the fact that its deterrents feel that the Younger Dryas can be explained more simply as a climate event unto itself. Critics primarily argue that meltwater from the glaciers at the end of the Pleistocene spilled into the Atlantic as global temperatures began to naturally warm, causing a cooling effect that disrupted ocean currents that led to further cooling prevalent throughout the Northern Hemispheres. Further, it has been noted that periods of cold reversal similar to the Dryas appear in the geological record toward the end of past ice ages as well; it seems unlikely that a cosmic impact event would occur at the end of every ice age.

Nonetheless, the accumulation of new evidence over the last few years makes the once unlikely theory of a cosmic impact 12,800 years ago now something worthy of a second look. Hence, the question is perhaps not so much one of “where is the evidence,” but instead who is willing to look at it?
https://mysteriousuniverse.org/2019...for-younger-dryas-impact-hypothesis-in-chile/
 

TenEightyOne

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Wiki has a good explanation (with good sources) of why peer reviews of the stuff published in support of the Impact Hypothesis find highly questionable errors. It remains on the table as a hypothesis but the search for evidence hasn't turned up repeatable results and in fact raises more negative evidence than positive.
Sorry, I couldn't access that English wiki server. Maybe you could copy and paste.

Anyway, I know the Younger Dryas is a very hot topic of late. Megafaunal and Clovis extinctions together with the black mat, nano diamonds, glass spherules, fission tracks etc. are not well understood or explained. The impact hypothesis has the problem of a lack of craters. My favorite hypothesis remains that of the solar outburst. But science is now hot on the track and will figure it out as ever more evidence is uncovered. :)
 

TenEightyOne

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Sorry, I couldn't access that English wiki server. Maybe you could copy and paste.

Copy/pasted below as-is, not sure why you'd be unable to access it? Black mat, nano diamonds (or modern insect poo) et al are covered therewithin.

Younger Dryas impact hypothesis
From Wikipedia, the free encyclopedia


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The Younger Dryas impact hypothesis or Clovis comet hypothesis originally proposed that a large air burst or earth impact of one or more comets initiated the Younger Dryas cold period about 12,900 BP calibrated (10,900 14C uncalibrated) years ago.[1][2][3] The hypothesis has been contested by research as recently as 2017, arguing that most of the conclusions cannot be repeated by other scientists, and criticized because of misinterpretation of data and previous lack of confirmatory evidence.[4][5][6][7]

The current impact hypothesis states that the air burst(s) or impact(s) of a swarm of carbonaceous chondrites or comet fragments set areas of the North American continent on fire, causing the extinction of most of the megafauna in North America and the demise of the North American Clovis culture after the last glacial period.[8] The Younger Dryas ice age lasted for about 1,200 years before the climate warmed again. The Hiawatha Glacier impact crater in Greenland is offered as evidence for the Younger Dryas impact hypothesis, due to its location and the speculative possibility that could be simultaneous with the start of the Younger Dryas cold period and megafauna extinctions which occurred approximately around the same era.[9]

Contents
Evidence[edit]
The evidence given by proponents of an impact event includes "black mats" of organic-rich soil that have been found at some 50 Clovis sites across the continent. Proponents have reported materials (nanodiamonds, metallic microspherules, carbon spherules, magnetic spherules, iridium, platinum, charcoal, soot, and fullerenes enriched in helium-3), which they interpret to be potential evidence of an impact event, at the very bottom of black mats of organic material that marks the beginning of the Younger Dryas,[10][11] and it is claimed these cannot be explained by volcanic, anthropogenic, or other natural processes.[3]

Research has been reported that at Lake Cuitzeo, in the central Mexican state of Guanajuato, evidence supporting a modified version of the Younger Dryas impact hypothesis—involving a much smaller, non-cometary impactor—was found in lake bed cores dating to 12,900 BP. The reported evidence included nanodiamonds (including the hexagonal form called lonsdaleite), carbon spherules, and magnetic spherules. Multiple hypotheses were examined to account for these observations, though none were believed to be terrestrial. Lonsdaleite occurs naturally in asteroids and cosmic dust and as a result of extraterrestrial impacts on Earth. The results of the study has not been replicated by other researchers.[12] Lonsdaleite has also been made artificially in laboratories.[13][14]

A 100-fold spike in the concentration of platinum has also been found in Greenland ice cores, dated to 12,890 BP with 5-year accuracy.[15] A much weaker Pt anomaly was subsequently reported with approximate age dating at 11 continental Younger Dryas sites.[16]

Another study, related to this hypothesis, by Antonio Zamora[17] provides a model of the formation of the Carolina Bays as an indirect consequence of an impact of a comet-like body on the Laurentide Ice Sheet that ejected ice boulders in ballistic trajectories that created the Bays all heading to the Great Lakes Region. It also provides an explanation about the formation of Nebraska's Rainwater Basins and why they are all pointing to the Lakes Region too. However, this study does not apply the widely accepted standards for identifying and confirming terrestrial impact structures. [18]

In the paleothological-archaeological site of Pilauco Bajo, Chile, there is evidence in sediment layers with charcoal and pollen assemblages both indicating major disturbances.[19] Other features found are rare metallic spherules, melt glass and nanodiamonds claimed to be derivative of airbursts or impacts.[19] All of this features have been dated to 12,800 BP.[19] So far Pilauco Bajo is the southernmost site where evidence of the Younger Dryas impacts have been found showing that a possible Younger Dryas strewn field covers at least 30% of Earth's radius.[19]

Consequences of hypothetical impact[edit]
It is conjectured that this impact event brought about the extinction of many species of North American Pleistocene megafauna. These animals included camels, mammoths, the giant short-faced bear, and numerous other species that the proponents suggest died out at this time.[20] The proposed markers for the impact event are claimed to appear at the end of the Clovis culture.[21]

History of the hypothesis[edit]
The initial description of this hypothesis was published in a 2006 book.[1] The following year, a paper with the same principal authors suggested that the impact event may have led to an immediate decline in human populations in North America at that time.[2]

Additional data purported to support the synchronous nature of the black mats was published. The authors stated that the data required further analysis, and independent analysis of other Clovis sites for verification of this evidence. The authors stated that they remained skeptical of the bolide impact hypothesis as the cause of the Younger Dryas and the megafaunal extinction. They also concluded that "...something major happened at 10,900 B.P. (14C uncalibrated) that we have yet to understand."[22]

Transmission electron microscopy evidence purported to show nanodiamonds from a layer assumed to correspond to the geologic moment of the event was published in the journal Science.[23] Also, in the same issue, D.J. Kennett reported that the nanodiamonds were evidence for bolide impacts from a rare swarm of carbonaceous chondrites or comets at the start of Younger Dryas, resulting from multiple airbursts and surface impacts. This resulted in substantial loss of plant life, megafauna and other animals.[8]

This study has been strenuously disputed by some scientists for a variety of technical and professional reasons. Skepticism increased with the revelation of documentation demonstrating misconduct and past criminal conduct (conviction for fraud and misrepresentation of credentials) by the researcher who prepared samples for the proponents of the hypothesis.[24] However, those charges were later dismissed and expunged by the court.[25][26]

The disputing scientists claim that the study's conclusions could not be repeated, that further research suggests that no nanodiamonds were found,[27] and that the supposed carbon spherules were, in fact, either fungus or insect feces and included modern contaminants.[6][28]

Some of the original proponents published a re-evaluation in June 2013 of spherules from 18 sites worldwide which they interpret to support their hypothesis.[11] Further analysis of Younger Dryas boundary sediments at 9 sites, released in June 2016, found no evidence of an extraterrestrial impact at the YDB.[29] In December 2016, an analysis of nanodiamond evidence failed to uncover lonsdaleite or a spike in nanodiamond concentration at the YDB.[30] Radiocarbon dating, microscopy of paleobotanical samples, and analytical pyrolysis of fluvial sediments "[found] no evidence in Arlington Canyon for an extraterrestrial impact or catastrophic impact-induced fire."[31] Exposed fluvial sequences in Arlington Canyon on Santa Rosa Island "features centrally in the controversial hypothesis of an extra-terrestrial impact at the onset of the Younger Dryas."[31]

In 2018 two new papers were published dealing with a "Extraordinary Biomass-Burning Episode" associated with the Younger Dryas Impact.[32][33]

Criticism[edit]
Criticism of chronology and age-dating[edit]
A study of Paleoindian demography found no evidence of a population decline among the Paleoindians at 12,900 ± 100 BP, which was inconsistent with predictions of an impact event.[34] They suggested that the hypothesis would probably need to be revised.[35][36] There is also no evidence of continent-wide wildfires at any time during terminal Pleistocene deglaciation,[37] though there is evidence that most larger wildfires had a human origin,[37] which calls into question the origin of the "black mat."[38] Iridium, magnetic minerals, microspherules, carbon, and nanodiamonds are all subject to differing interpretations as to their nature and origin, and may be explained in many cases by purely terrestrial or non-catastrophic factors.[39]

There is evidence that the megafaunal extinctions that occurred across northern Eurasia, North America, and South America at the end of the Pleistocene were not synchronous. The extinctions in South America appear to have occurred at least 400 years after the extinctions in North America.[40][41][42] The extinction of woolly mammoths in Siberia also appears to have occurred later than in North America.[40] A greater disparity in extinction timings is apparent in island megafaunal extinctions that lagged nearby continental extinctions by thousands of years; examples include the survival of woolly mammoths on Wrangel Island, Russia, until 3700 BP,[40][41][43] and the survival of ground sloths in the Antilles,[44] the Caribbean, until 4700 cal BP.[40] The Australian megafaunal extinctions occurred approximately 30,000 years earlier than the hypothetical Younger Dryas event.[45]

The megafaunal extinction pattern observed in North America poses a problem for the bolide impact scenario, since it raises the question why large mammals should be preferentially exterminated over small mammals or other vertebrates.[46] Additionally, some extant megafaunal species such as bison and Brown bear seem to have been little affected by the extinction event, while the environmental devastation caused by a bolide impact would not be expected to discriminate.[40] Also, it appears that there was collapse in North American megafaunal population from 14,800 to 13,700 BP, well before the date of the hypothetical extraterrestrial impact,[47] possibly from anthropogenic activities, including hunting.[21]

Other research has shown no support for the impact hypothesis. One group examined carbon-14 dates for charcoal particles that showed wildfires occurred well after the proposed impact date, and the glass-like carbon was produced by wildfires and no lonsdaleite was found.[48]

Disputed origin and ocurrence of physical evidence[edit]
Scientists have asserted that the carbon spherules originated as fungal structures and/or insect fecal pellets, and contained modern contaminants[6][28] and that the claimed nanodiamonds are actually misidentified graphene and graphene/graphane oxide aggregates.[27][49] An analysis of a similar Younger Dryas boundary layer in Belgium yielded carbon crystalline structures such as nanodiamonds, but the authors concluded that they also did not show unique evidence for a bolide impact.[50] Researchers have also found no extraterrestrial platinum group metals in the boundary layer, which is inconsistent with the hypothesized impact event.[51] Further independent analysis was unable to confirm prior claims of magnetic particles and microspherules, concluding that there was no evidence for a Younger Dryas impact event.[52]

Analysis of fluvial sediments on Santa Rosa Island by another group also found no evidence of lonsdaleite, impact-induced fires, or extraterrestrial impact.[31]

Research published in 2012 has shown that the so-called "black mats" are easily explained by typical earth processes in wetland environments.[5] The study of black mats, that are common in prehistorical wetland deposits which represent shallow marshlands, that were from 6000 to 40,000 years ago in the southwestern USA and Atacama Desert in Chile, showed elevated concentrations of iridium and magnetic sediments, magnetic spherules and titanomagnetite grains. It was suggested that because these markers are found within or at the base of black mats, irrespective of age or location, suggests that these markers arise from processes common to wetland systems, and probably not as a result of catastrophic bolide impacts.[5]

A 2013 study found a spike in platinum in Greenland ice. The authors of that study conclude that such a small impact of an iron meteorite is “unlikely to result in an airburst or trigger wide wildfires proposed by the YDB impact hypothesis."[53] But they write that the large Pt anomaly "hints for an extraterrestrial source of Pt," showing that any disagreement with the proponents of the original YDIH is over the nature of the extraterrestrial object, not whether there was one, and it is much more likely that the Greenland Pt anomaly was caused by a small local iron meteorite fall without any widespread consequences. [54]

Researchers have also criticized the conclusions of various studies for incorrect age-dating of the sediments,[55] contamination by modern carbon, inconsistent hypothesis that made it difficult to predict the type and size of bolide,[56] lack of proper identification of lonsdaleite,[57] confusing an extraterrestrial impact with other causes such as fire,[58] and for inconsistent use of the carbon spherule "proxy".[59] Naturally occurring lonsdaleite has also been identified in non-bolide diamond placer deposits in the Sakha Republic.[14]

Proponents of the hypothesis have responded to defend their findings, disputing the accusation of irreproducibility or replicating their findings.[60][61][62][63][64][65][excessive citations]:Details should be specified and individually cited Critics of the hypothesis have repeatedly addressed the responses, and have published counterarguments.[66] [67] [68] [69] [70] [71] [72] [73] [74][75][excessive citations]

In 2018, a team of scientists published evidence for an impact crater of unknown age under the Hiawatha Glacier in Greenland[76] Even though the research paper did not suggest any connection to the Younger Dryas, some scientists speculated without evidence about such a link in news reports.[77][78] Skeptics reject this connection because it would require an improbably recent impact — an impact of this size should occur only once every few million years — and it would leave evidence, such as a young ejecta blanket.[78] Moreover, this has not yet been accepted as a confirmed impact crater. Christian Koeberl, an impact crater expert from the University of Vienna, was quoted in Popular Science saying: “The authors report on some interesting phenomena, but the ‘definitive’ interpretation and conclusion that a large impact crater underneath the ice has been discovered is a severe over-interpretation of the existing data.”[79]

See also[edit]
References[edit]
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  15. ^ Petaev MI, Huang S, Jacobsen SB, Zindler A (August 2013). "Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas". Proceedings of the National Academy of Sciences of the United States of America. 110 (32): 12917–20. Bibcode:2013PNAS..11012917P. doi:10.1073/pnas.1303924110. PMC 3740870. PMID 23878232.
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  17. ^ Zamora, Antonio (2017). "A model for the geomorphology of the Carolina Bays". Geomorphology. 282: 209–216. Bibcode:2017Geomo.282..209Z. doi:10.1016/j.geomorph.2017.01.019.
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  47. ^ Gill JL, Williams JW, Jackson ST, Lininger KB, Robinson GS (November 2009). "Pleistocene megafaunal collapse, novel plant communities, and enhanced fire regimes in North America"(PDF). Science. 326 (5956): 1100–3. Bibcode:2009Sci...326.1100G. doi:10.1126/science.1179504. PMID 19965426.
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  51. ^ Paquay FS, Goderis S, Ravizza G, Vanhaeck F, Boyd M, Surovell TA, Holliday VT, Haynes CV, Claeys P (December 2009). "Absence of geochemical evidence for an impact event at the Bølling-Allerød/Younger Dryas transition". Proceedings of the National Academy of Sciences of the United States of America. 106 (51): 21505–10. Bibcode:2009PNAS..10621505P. doi:10.1073/pnas.0908874106. PMC 2799824. PMID 20007789.
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  53. ^ Petaev MI, Huang S, Jacobsen SB, Zindler A (August 2013). "Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas". Proceedings of the National Academy of Sciences of the United States of America. 110 (32): 12917–20. Bibcode:2013PNAS..11012917P. doi:10.1073/pnas.1303924110. PMC 3740870. PMID 23878232.
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Younger Dryas impact hypothesis
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The Younger Dryas impact hypothesis or Clovis comet hypothesis originally proposed that a large air burst or earth impact of one or more comets initiated the Younger Dryas cold period about 12,900 BP calibrated (10,900 14C uncalibrated) years ago.[1][2][3] The hypothesis has been contested by research as recently as 2017, arguing that most of the conclusions cannot be repeated by other scientists, and criticized because of misinterpretation of data and previous lack of confirmatory evidence.[4][5][6][7]

The current impact hypothesis states that the air burst(s) or impact(s) of a swarm of carbonaceous chondrites or comet fragments set areas of the North American continent on fire, causing the extinction of most of the megafauna in North America and the demise of the North American Clovis culture after the last glacial period.[8] The Younger Dryas ice age lasted for about 1,200 years before the climate warmed again. The Hiawatha Glacier impact crater in Greenland is offered as evidence for the Younger Dryas impact hypothesis, due to its location and the speculative possibility that could be simultaneous with the start of the Younger Dryas cold period and megafauna extinctions which occurred approximately around the same era.[9]

Contents
Evidence[edit]
The evidence given by proponents of an impact event includes "black mats" of organic-rich soil that have been found at some 50 Clovis sites across the continent. Proponents have reported materials (nanodiamonds, metallic microspherules, carbon spherules, magnetic spherules, iridium, platinum, charcoal, soot, and fullerenes enriched in helium-3), which they interpret to be potential evidence of an impact event, at the very bottom of black mats of organic material that marks the beginning of the Younger Dryas,[10][11] and it is claimed these cannot be explained by volcanic, anthropogenic, or other natural processes.[3]

Research has been reported that at Lake Cuitzeo, in the central Mexican state of Guanajuato, evidence supporting a modified version of the Younger Dryas impact hypothesis—involving a much smaller, non-cometary impactor—was found in lake bed cores dating to 12,900 BP. The reported evidence included nanodiamonds (including the hexagonal form called lonsdaleite), carbon spherules, and magnetic spherules. Multiple hypotheses were examined to account for these observations, though none were believed to be terrestrial. Lonsdaleite occurs naturally in asteroids and cosmic dust and as a result of extraterrestrial impacts on Earth. The results of the study has not been replicated by other researchers.[12] Lonsdaleite has also been made artificially in laboratories.[13][14]

A 100-fold spike in the concentration of platinum has also been found in Greenland ice cores, dated to 12,890 BP with 5-year accuracy.[15] A much weaker Pt anomaly was subsequently reported with approximate age dating at 11 continental Younger Dryas sites.[16]

Another study, related to this hypothesis, by Antonio Zamora[17] provides a model of the formation of the Carolina Bays as an indirect consequence of an impact of a comet-like body on the Laurentide Ice Sheet that ejected ice boulders in ballistic trajectories that created the Bays all heading to the Great Lakes Region. It also provides an explanation about the formation of Nebraska's Rainwater Basins and why they are all pointing to the Lakes Region too. However, this study does not apply the widely accepted standards for identifying and confirming terrestrial impact structures. [18]

In the paleothological-archaeological site of Pilauco Bajo, Chile, there is evidence in sediment layers with charcoal and pollen assemblages both indicating major disturbances.[19] Other features found are rare metallic spherules, melt glass and nanodiamonds claimed to be derivative of airbursts or impacts.[19] All of this features have been dated to 12,800 BP.[19] So far Pilauco Bajo is the southernmost site where evidence of the Younger Dryas impacts have been found showing that a possible Younger Dryas strewn field covers at least 30% of Earth's radius.[19]

Consequences of hypothetical impact[edit]
It is conjectured that this impact event brought about the extinction of many species of North American Pleistocene megafauna. These animals included camels, mammoths, the giant short-faced bear, and numerous other species that the proponents suggest died out at this time.[20] The proposed markers for the impact event are claimed to appear at the end of the Clovis culture.[21]

History of the hypothesis[edit]
The initial description of this hypothesis was published in a 2006 book.[1] The following year, a paper with the same principal authors suggested that the impact event may have led to an immediate decline in human populations in North America at that time.[2]

Additional data purported to support the synchronous nature of the black mats was published. The authors stated that the data required further analysis, and independent analysis of other Clovis sites for verification of this evidence. The authors stated that they remained skeptical of the bolide impact hypothesis as the cause of the Younger Dryas and the megafaunal extinction. They also concluded that "...something major happened at 10,900 B.P. (14C uncalibrated) that we have yet to understand."[22]

Transmission electron microscopy evidence purported to show nanodiamonds from a layer assumed to correspond to the geologic moment of the event was published in the journal Science.[23] Also, in the same issue, D.J. Kennett reported that the nanodiamonds were evidence for bolide impacts from a rare swarm of carbonaceous chondrites or comets at the start of Younger Dryas, resulting from multiple airbursts and surface impacts. This resulted in substantial loss of plant life, megafauna and other animals.[8]

This study has been strenuously disputed by some scientists for a variety of technical and professional reasons. Skepticism increased with the revelation of documentation demonstrating misconduct and past criminal conduct (conviction for fraud and misrepresentation of credentials) by the researcher who prepared samples for the proponents of the hypothesis.[24] However, those charges were later dismissed and expunged by the court.[25][26]

The disputing scientists claim that the study's conclusions could not be repeated, that further research suggests that no nanodiamonds were found,[27] and that the supposed carbon spherules were, in fact, either fungus or insect feces and included modern contaminants.[6][28]

Some of the original proponents published a re-evaluation in June 2013 of spherules from 18 sites worldwide which they interpret to support their hypothesis.[11] Further analysis of Younger Dryas boundary sediments at 9 sites, released in June 2016, found no evidence of an extraterrestrial impact at the YDB.[29] In December 2016, an analysis of nanodiamond evidence failed to uncover lonsdaleite or a spike in nanodiamond concentration at the YDB.[30] Radiocarbon dating, microscopy of paleobotanical samples, and analytical pyrolysis of fluvial sediments "[found] no evidence in Arlington Canyon for an extraterrestrial impact or catastrophic impact-induced fire."[31] Exposed fluvial sequences in Arlington Canyon on Santa Rosa Island "features centrally in the controversial hypothesis of an extra-terrestrial impact at the onset of the Younger Dryas."[31]

In 2018 two new papers were published dealing with a "Extraordinary Biomass-Burning Episode" associated with the Younger Dryas Impact.[32][33]

Criticism[edit]
Criticism of chronology and age-dating[edit]
A study of Paleoindian demography found no evidence of a population decline among the Paleoindians at 12,900 ± 100 BP, which was inconsistent with predictions of an impact event.[34] They suggested that the hypothesis would probably need to be revised.[35][36] There is also no evidence of continent-wide wildfires at any time during terminal Pleistocene deglaciation,[37] though there is evidence that most larger wildfires had a human origin,[37] which calls into question the origin of the "black mat."[38] Iridium, magnetic minerals, microspherules, carbon, and nanodiamonds are all subject to differing interpretations as to their nature and origin, and may be explained in many cases by purely terrestrial or non-catastrophic factors.[39]

There is evidence that the megafaunal extinctions that occurred across northern Eurasia, North America, and South America at the end of the Pleistocene were not synchronous. The extinctions in South America appear to have occurred at least 400 years after the extinctions in North America.[40][41][42] The extinction of woolly mammoths in Siberia also appears to have occurred later than in North America.[40] A greater disparity in extinction timings is apparent in island megafaunal extinctions that lagged nearby continental extinctions by thousands of years; examples include the survival of woolly mammoths on Wrangel Island, Russia, until 3700 BP,[40][41][43] and the survival of ground sloths in the Antilles,[44] the Caribbean, until 4700 cal BP.[40] The Australian megafaunal extinctions occurred approximately 30,000 years earlier than the hypothetical Younger Dryas event.[45]

The megafaunal extinction pattern observed in North America poses a problem for the bolide impact scenario, since it raises the question why large mammals should be preferentially exterminated over small mammals or other vertebrates.[46] Additionally, some extant megafaunal species such as bison and Brown bear seem to have been little affected by the extinction event, while the environmental devastation caused by a bolide impact would not be expected to discriminate.[40] Also, it appears that there was collapse in North American megafaunal population from 14,800 to 13,700 BP, well before the date of the hypothetical extraterrestrial impact,[47] possibly from anthropogenic activities, including hunting.[21]

Other research has shown no support for the impact hypothesis. One group examined carbon-14 dates for charcoal particles that showed wildfires occurred well after the proposed impact date, and the glass-like carbon was produced by wildfires and no lonsdaleite was found.[48]

Disputed origin and ocurrence of physical evidence[edit]
Scientists have asserted that the carbon spherules originated as fungal structures and/or insect fecal pellets, and contained modern contaminants[6][28] and that the claimed nanodiamonds are actually misidentified graphene and graphene/graphane oxide aggregates.[27][49] An analysis of a similar Younger Dryas boundary layer in Belgium yielded carbon crystalline structures such as nanodiamonds, but the authors concluded that they also did not show unique evidence for a bolide impact.[50] Researchers have also found no extraterrestrial platinum group metals in the boundary layer, which is inconsistent with the hypothesized impact event.[51] Further independent analysis was unable to confirm prior claims of magnetic particles and microspherules, concluding that there was no evidence for a Younger Dryas impact event.[52]

Analysis of fluvial sediments on Santa Rosa Island by another group also found no evidence of lonsdaleite, impact-induced fires, or extraterrestrial impact.[31]

Research published in 2012 has shown that the so-called "black mats" are easily explained by typical earth processes in wetland environments.[5] The study of black mats, that are common in prehistorical wetland deposits which represent shallow marshlands, that were from 6000 to 40,000 years ago in the southwestern USA and Atacama Desert in Chile, showed elevated concentrations of iridium and magnetic sediments, magnetic spherules and titanomagnetite grains. It was suggested that because these markers are found within or at the base of black mats, irrespective of age or location, suggests that these markers arise from processes common to wetland systems, and probably not as a result of catastrophic bolide impacts.[5]

A 2013 study found a spike in platinum in Greenland ice. The authors of that study conclude that such a small impact of an iron meteorite is “unlikely to result in an airburst or trigger wide wildfires proposed by the YDB impact hypothesis."[53] But they write that the large Pt anomaly "hints for an extraterrestrial source of Pt," showing that any disagreement with the proponents of the original YDIH is over the nature of the extraterrestrial object, not whether there was one, and it is much more likely that the Greenland Pt anomaly was caused by a small local iron meteorite fall without any widespread consequences. [54]

Researchers have also criticized the conclusions of various studies for incorrect age-dating of the sediments,[55] contamination by modern carbon, inconsistent hypothesis that made it difficult to predict the type and size of bolide,[56] lack of proper identification of lonsdaleite,[57] confusing an extraterrestrial impact with other causes such as fire,[58] and for inconsistent use of the carbon spherule "proxy".[59] Naturally occurring lonsdaleite has also been identified in non-bolide diamond placer deposits in the Sakha Republic.[14]

Proponents of the hypothesis have responded to defend their findings, disputing the accusation of irreproducibility or replicating their findings.[60][61][62][63][64][65][excessive citations]:Details should be specified and individually cited Critics of the hypothesis have repeatedly addressed the responses, and have published counterarguments.[66] [67] [68] [69] [70] [71] [72] [73] [74][75][excessive citations]

In 2018, a team of scientists published evidence for an impact crater of unknown age under the Hiawatha Glacier in Greenland[76] Even though the research paper did not suggest any connection to the Younger Dryas, some scientists speculated without evidence about such a link in news reports.[77][78] Skeptics reject this connection because it would require an improbably recent impact — an impact of this size should occur only once every few million years — and it would leave evidence, such as a young ejecta blanket.[78] Moreover, this has not yet been accepted as a confirmed impact crater. Christian Koeberl, an impact crater expert from the University of Vienna, was quoted in Popular Science saying: “The authors report on some interesting phenomena, but the ‘definitive’ interpretation and conclusion that a large impact crater underneath the ice has been discovered is a severe over-interpretation of the existing data.”[79]

See also[edit]
References[edit]
  1. ^ Jump up to:a b Firestone R, West A, Warwick-Smith S (4 June 2006). The Cycle of Cosmic Catastrophes: How a Stone-Age Comet Changed the Course of World Culture. Bear & Company. p. 392. ISBN 978-1591430612.
  2. ^ Jump up to:a b Firestone RB, West A, Kennett JP, Becker L, Bunch TE, Revay ZS, et al. (October 2007). "Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling". Proceedings of the National Academy of Sciences of the United States of America. 104 (41): 16016–21. Bibcode:2007PNAS..10416016F. doi:10.1073/pnas.0706977104. PMC 1994902. PMID 17901202.
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  4. ^ Pinter N, Scott AC, Daulton TL, Podoll A, Koeberl C, Anderson RS, Ishman SE (2011). "The Younger Dryas impact hypothesis: A requiem". Earth-Science Reviews. 106 (3–4): 247. Bibcode:2011ESRv..106..247P. doi:10.1016/j.earscirev.2011.02.005.
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  50. ^ Tian H, Schryvers D, Claeys P (January 2011). "Nanodiamonds do not provide unique evidence for a Younger Dryas impact". Proceedings of the National Academy of Sciences of the United States of America. 108 (1): 40–4. Bibcode:2011PNAS..108...40T. doi:10.1073/pnas.1007695108. PMC 3017148. PMID 21173270.
  51. ^ Paquay FS, Goderis S, Ravizza G, Vanhaeck F, Boyd M, Surovell TA, Holliday VT, Haynes CV, Claeys P (December 2009). "Absence of geochemical evidence for an impact event at the Bølling-Allerød/Younger Dryas transition". Proceedings of the National Academy of Sciences of the United States of America. 106 (51): 21505–10. Bibcode:2009PNAS..10621505P. doi:10.1073/pnas.0908874106. PMC 2799824. PMID 20007789.
  52. ^ Surovell TA, Holliday VT, Gingerich JA, Ketron C, Haynes CV, Hilman I, Wagner DP, Johnson E, Claeys P (October 2009). "An independent evaluation of the Younger Dryas extraterrestrial impact hypothesis". Proceedings of the National Academy of Sciences of the United States of America. 106 (43): 18155–8. Bibcode:2009PNAS..10618155S. doi:10.1073/pnas.0907857106. PMC 2775309. PMID 19822748.
  53. ^ Petaev MI, Huang S, Jacobsen SB, Zindler A (August 2013). "Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas". Proceedings of the National Academy of Sciences of the United States of America. 110 (32): 12917–20. Bibcode:2013PNAS..11012917P. doi:10.1073/pnas.1303924110. PMC 3740870. PMID 23878232.
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Yep, just has I said; hot, controversial and needing further understanding and explanation. Solar Outburst coming up on the inside track!

In the Philosophy of Science there has been waging a generations-long contest between Uniformitarians and Catastrophists. My father was a petroleum geologist and a Catastrophist ahead of his time. Way back then, he had to stay in the closet and keep his mouth shut.
 
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"superflares with energy > 10^34* erg would be approximately once every 2000 – 3000 years on old Sun-like stars"

https://arxiv.org/pdf/1904.00142.pdf (page 43)

* 100-1000 greater than the 1859 Carrington Event (10^32 erg)

We note here that several potential candidates of extreme solar flare events, which can be bigger than the largest solar flare in the past 200 years (Eflare ∼10^32 erg), have been reported from the data over the recent 1000 – 2000 years (e.g., Usoskin 2017 for review). For example, significant radioisotope 14C enhancements have been reported in tree rings for the year 775AD and 994AD, and they suggest extremely strong and rapid cosmic-ray increase events possibly caused by extreme solar flares (e.g., Miyake et al. 2012&2013).
 

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A mysterious growing hotspot in Yellowstone's giant caldera volcano is killing trees and vegetation.


img7228_400w_309h.jpg

Landsat-8 nighttime thermal infrared image from April 2017 showing the Tern Lake area. In Yellowstone, temperatures are extremely cold at night in the winter, and most lakes are frozen (dark pixels). West Tern Lake seems to be thawing here - perhaps it receives some thermal waters from nearby hot springs. The patch of bright (warm) pixels between West Tern Lake and the Tern Lake thermal area has emerged over the last 20 years. Lakes are outlined in blue; the boundary of the Sour Creek resurgent dome is in black; known thermal areas are outlined in red; and the red triangles are individual thermal features that have been mapped.
https://volcanoes.usgs.gov/volcanoes/yellowstone/article_home.html?vaid=160

img7226_400w_439h.jpg

Map of thermal areas in Yellowstone National Park. Most of Yellowstone's more than 10,000 thermal features are clustered together into about 120 distinct thermal areas (shown in red). Lakes are blue. The Yellowstone Caldera is solid black and the resurgent domes are dotted black. Roads are yellow. The orange box shows the location of the Tern Lake thermal area.
 

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Earth is currently undergoing a geomagnetic excursion; the poles, especially the North Pole, is moving significantly and the magnetic field is precipitously losing strength. In the past, these sorts of events are associated with extinctions of species, including humans. IMO, our climate in a serious way is cyclical, and is paced by events taking place at the earth's core and at the solar system level, mainly the Sun, and by cosmic rays.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018RG000629




Review Article
The role of geomagnetic field intensity in late Quaternary evolution of humans and large mammals
J.E.T. Channell

L. Vigliotti
First published: 29 May 2019

https://doi.org/10.1029/2018RG000629
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1029/2018RG000629


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

Plain Language Summary
The strength of Earth's magnetic field in the past, recorded by rocks and sediments, provides a proxy for past flux of ultra‐violet radiation (UVR) to Earth's surface due to the role of the field in modulating stratigraphic ozone. About 40 thousand years ago, mammalian fossils in Australia and Eurasia record an important die‐off of large mammals that included Neanderthals in Europe. In the Americas and Europe, a large mammalian die‐off appears to have occurred ~13 thousand years ago. Both die‐offs can be linked to minima in Earth's magnetic field strength implying that UVR flux variations to Earth's surface influenced mammalian evolution. For the last ~200 thousand years, estimates of the timing of branching episodes in the human evolutionary tree, from modern and fossil DNA and Y‐chromosomes, can be linked to minima in field strength which implies a long‐term role for UVR in human evolution. New fossil finds, improved fossil dating, knowledge of the past strength of Earth's magnetic field, and refinements in the human evolutionary tree, are sharpening the focus on a possible link between UVR arriving at the Earth's surface, magnetic field strength, and events in mammalian evolution.



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Accepted, unedited articles published online and citable. The final edited and typeset version of record will appear in the future.
 

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Another sort of apocalypse, really an extinction of species, is the type that takes place slowly but surely over many generations. The demise of the Neanderthals may have happened this way. I live in the Pacific Northwest of the US where earthquakes, floods, volcanoes and glaciers have all drastically reshaped the landscape over the last 13,000 years. I live under the shadow of prospective geological disaster. But today we consider UVR induced genetic change due to a brief geomagnetic excursion. Not much for humans to worry about, but plants, animals, agriculture, weather, and climate are significantly affected.

 

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Copy/pasted below as-is, not sure why you'd be unable to access it? Black mat, nano diamonds (or modern insect poo) et al are covered therewithin.

Younger Dryas impact hypothesis
From Wikipedia, the free encyclopedia


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The Younger Dryas impact hypothesis or Clovis comet hypothesis originally proposed that a large air burst or earth impact of one or more comets initiated the Younger Dryas cold period about 12,900 BP calibrated (10,900 14C uncalibrated) years ago.[1][2][3] The hypothesis has been contested by research as recently as 2017, arguing that most of the conclusions cannot be repeated by other scientists, and criticized because of misinterpretation of data and previous lack of confirmatory evidence.[4][5][6][7]

The current impact hypothesis states that the air burst(s) or impact(s) of a swarm of carbonaceous chondrites or comet fragments set areas of the North American continent on fire, causing the extinction of most of the megafauna in North America and the demise of the North American Clovis culture after the last glacial period.[8] The Younger Dryas ice age lasted for about 1,200 years before the climate warmed again. The Hiawatha Glacier impact crater in Greenland is offered as evidence for the Younger Dryas impact hypothesis, due to its location and the speculative possibility that could be simultaneous with the start of the Younger Dryas cold period and megafauna extinctions which occurred approximately around the same era.[9]

Contents
Evidence[edit]
The evidence given by proponents of an impact event includes "black mats" of organic-rich soil that have been found at some 50 Clovis sites across the continent. Proponents have reported materials (nanodiamonds, metallic microspherules, carbon spherules, magnetic spherules, iridium, platinum, charcoal, soot, and fullerenes enriched in helium-3), which they interpret to be potential evidence of an impact event, at the very bottom of black mats of organic material that marks the beginning of the Younger Dryas,[10][11] and it is claimed these cannot be explained by volcanic, anthropogenic, or other natural processes.[3]

Research has been reported that at Lake Cuitzeo, in the central Mexican state of Guanajuato, evidence supporting a modified version of the Younger Dryas impact hypothesis—involving a much smaller, non-cometary impactor—was found in lake bed cores dating to 12,900 BP. The reported evidence included nanodiamonds (including the hexagonal form called lonsdaleite), carbon spherules, and magnetic spherules. Multiple hypotheses were examined to account for these observations, though none were believed to be terrestrial. Lonsdaleite occurs naturally in asteroids and cosmic dust and as a result of extraterrestrial impacts on Earth. The results of the study has not been replicated by other researchers.[12] Lonsdaleite has also been made artificially in laboratories.[13][14]

A 100-fold spike in the concentration of platinum has also been found in Greenland ice cores, dated to 12,890 BP with 5-year accuracy.[15] A much weaker Pt anomaly was subsequently reported with approximate age dating at 11 continental Younger Dryas sites.[16]

Another study, related to this hypothesis, by Antonio Zamora[17] provides a model of the formation of the Carolina Bays as an indirect consequence of an impact of a comet-like body on the Laurentide Ice Sheet that ejected ice boulders in ballistic trajectories that created the Bays all heading to the Great Lakes Region. It also provides an explanation about the formation of Nebraska's Rainwater Basins and why they are all pointing to the Lakes Region too. However, this study does not apply the widely accepted standards for identifying and confirming terrestrial impact structures. [18]

In the paleothological-archaeological site of Pilauco Bajo, Chile, there is evidence in sediment layers with charcoal and pollen assemblages both indicating major disturbances.[19] Other features found are rare metallic spherules, melt glass and nanodiamonds claimed to be derivative of airbursts or impacts.[19] All of this features have been dated to 12,800 BP.[19] So far Pilauco Bajo is the southernmost site where evidence of the Younger Dryas impacts have been found showing that a possible Younger Dryas strewn field covers at least 30% of Earth's radius.[19]

Consequences of hypothetical impact[edit]
It is conjectured that this impact event brought about the extinction of many species of North American Pleistocene megafauna. These animals included camels, mammoths, the giant short-faced bear, and numerous other species that the proponents suggest died out at this time.[20] The proposed markers for the impact event are claimed to appear at the end of the Clovis culture.[21]

History of the hypothesis[edit]
The initial description of this hypothesis was published in a 2006 book.[1] The following year, a paper with the same principal authors suggested that the impact event may have led to an immediate decline in human populations in North America at that time.[2]

Additional data purported to support the synchronous nature of the black mats was published. The authors stated that the data required further analysis, and independent analysis of other Clovis sites for verification of this evidence. The authors stated that they remained skeptical of the bolide impact hypothesis as the cause of the Younger Dryas and the megafaunal extinction. They also concluded that "...something major happened at 10,900 B.P. (14C uncalibrated) that we have yet to understand."[22]

Transmission electron microscopy evidence purported to show nanodiamonds from a layer assumed to correspond to the geologic moment of the event was published in the journal Science.[23] Also, in the same issue, D.J. Kennett reported that the nanodiamonds were evidence for bolide impacts from a rare swarm of carbonaceous chondrites or comets at the start of Younger Dryas, resulting from multiple airbursts and surface impacts. This resulted in substantial loss of plant life, megafauna and other animals.[8]

This study has been strenuously disputed by some scientists for a variety of technical and professional reasons. Skepticism increased with the revelation of documentation demonstrating misconduct and past criminal conduct (conviction for fraud and misrepresentation of credentials) by the researcher who prepared samples for the proponents of the hypothesis.[24] However, those charges were later dismissed and expunged by the court.[25][26]

The disputing scientists claim that the study's conclusions could not be repeated, that further research suggests that no nanodiamonds were found,[27] and that the supposed carbon spherules were, in fact, either fungus or insect feces and included modern contaminants.[6][28]

Some of the original proponents published a re-evaluation in June 2013 of spherules from 18 sites worldwide which they interpret to support their hypothesis.[11] Further analysis of Younger Dryas boundary sediments at 9 sites, released in June 2016, found no evidence of an extraterrestrial impact at the YDB.[29] In December 2016, an analysis of nanodiamond evidence failed to uncover lonsdaleite or a spike in nanodiamond concentration at the YDB.[30] Radiocarbon dating, microscopy of paleobotanical samples, and analytical pyrolysis of fluvial sediments "[found] no evidence in Arlington Canyon for an extraterrestrial impact or catastrophic impact-induced fire."[31] Exposed fluvial sequences in Arlington Canyon on Santa Rosa Island "features centrally in the controversial hypothesis of an extra-terrestrial impact at the onset of the Younger Dryas."[31]

In 2018 two new papers were published dealing with a "Extraordinary Biomass-Burning Episode" associated with the Younger Dryas Impact.[32][33]

Criticism[edit]
Criticism of chronology and age-dating[edit]
A study of Paleoindian demography found no evidence of a population decline among the Paleoindians at 12,900 ± 100 BP, which was inconsistent with predictions of an impact event.[34] They suggested that the hypothesis would probably need to be revised.[35][36] There is also no evidence of continent-wide wildfires at any time during terminal Pleistocene deglaciation,[37] though there is evidence that most larger wildfires had a human origin,[37] which calls into question the origin of the "black mat."[38] Iridium, magnetic minerals, microspherules, carbon, and nanodiamonds are all subject to differing interpretations as to their nature and origin, and may be explained in many cases by purely terrestrial or non-catastrophic factors.[39]

There is evidence that the megafaunal extinctions that occurred across northern Eurasia, North America, and South America at the end of the Pleistocene were not synchronous. The extinctions in South America appear to have occurred at least 400 years after the extinctions in North America.[40][41][42] The extinction of woolly mammoths in Siberia also appears to have occurred later than in North America.[40] A greater disparity in extinction timings is apparent in island megafaunal extinctions that lagged nearby continental extinctions by thousands of years; examples include the survival of woolly mammoths on Wrangel Island, Russia, until 3700 BP,[40][41][43] and the survival of ground sloths in the Antilles,[44] the Caribbean, until 4700 cal BP.[40] The Australian megafaunal extinctions occurred approximately 30,000 years earlier than the hypothetical Younger Dryas event.[45]

The megafaunal extinction pattern observed in North America poses a problem for the bolide impact scenario, since it raises the question why large mammals should be preferentially exterminated over small mammals or other vertebrates.[46] Additionally, some extant megafaunal species such as bison and Brown bear seem to have been little affected by the extinction event, while the environmental devastation caused by a bolide impact would not be expected to discriminate.[40] Also, it appears that there was collapse in North American megafaunal population from 14,800 to 13,700 BP, well before the date of the hypothetical extraterrestrial impact,[47] possibly from anthropogenic activities, including hunting.[21]

Other research has shown no support for the impact hypothesis. One group examined carbon-14 dates for charcoal particles that showed wildfires occurred well after the proposed impact date, and the glass-like carbon was produced by wildfires and no lonsdaleite was found.[48]

Disputed origin and ocurrence of physical evidence[edit]
Scientists have asserted that the carbon spherules originated as fungal structures and/or insect fecal pellets, and contained modern contaminants[6][28] and that the claimed nanodiamonds are actually misidentified graphene and graphene/graphane oxide aggregates.[27][49] An analysis of a similar Younger Dryas boundary layer in Belgium yielded carbon crystalline structures such as nanodiamonds, but the authors concluded that they also did not show unique evidence for a bolide impact.[50] Researchers have also found no extraterrestrial platinum group metals in the boundary layer, which is inconsistent with the hypothesized impact event.[51] Further independent analysis was unable to confirm prior claims of magnetic particles and microspherules, concluding that there was no evidence for a Younger Dryas impact event.[52]

Analysis of fluvial sediments on Santa Rosa Island by another group also found no evidence of lonsdaleite, impact-induced fires, or extraterrestrial impact.[31]

Research published in 2012 has shown that the so-called "black mats" are easily explained by typical earth processes in wetland environments.[5] The study of black mats, that are common in prehistorical wetland deposits which represent shallow marshlands, that were from 6000 to 40,000 years ago in the southwestern USA and Atacama Desert in Chile, showed elevated concentrations of iridium and magnetic sediments, magnetic spherules and titanomagnetite grains. It was suggested that because these markers are found within or at the base of black mats, irrespective of age or location, suggests that these markers arise from processes common to wetland systems, and probably not as a result of catastrophic bolide impacts.[5]

A 2013 study found a spike in platinum in Greenland ice. The authors of that study conclude that such a small impact of an iron meteorite is “unlikely to result in an airburst or trigger wide wildfires proposed by the YDB impact hypothesis."[53] But they write that the large Pt anomaly "hints for an extraterrestrial source of Pt," showing that any disagreement with the proponents of the original YDIH is over the nature of the extraterrestrial object, not whether there was one, and it is much more likely that the Greenland Pt anomaly was caused by a small local iron meteorite fall without any widespread consequences. [54]

Researchers have also criticized the conclusions of various studies for incorrect age-dating of the sediments,[55] contamination by modern carbon, inconsistent hypothesis that made it difficult to predict the type and size of bolide,[56] lack of proper identification of lonsdaleite,[57] confusing an extraterrestrial impact with other causes such as fire,[58] and for inconsistent use of the carbon spherule "proxy".[59] Naturally occurring lonsdaleite has also been identified in non-bolide diamond placer deposits in the Sakha Republic.[14]

Proponents of the hypothesis have responded to defend their findings, disputing the accusation of irreproducibility or replicating their findings.[60][61][62][63][64][65][excessive citations]:Details should be specified and individually cited Critics of the hypothesis have repeatedly addressed the responses, and have published counterarguments.[66] [67] [68] [69] [70] [71] [72] [73] [74][75][excessive citations]

In 2018, a team of scientists published evidence for an impact crater of unknown age under the Hiawatha Glacier in Greenland[76] Even though the research paper did not suggest any connection to the Younger Dryas, some scientists speculated without evidence about such a link in news reports.[77][78] Skeptics reject this connection because it would require an improbably recent impact — an impact of this size should occur only once every few million years — and it would leave evidence, such as a young ejecta blanket.[78] Moreover, this has not yet been accepted as a confirmed impact crater. Christian Koeberl, an impact crater expert from the University of Vienna, was quoted in Popular Science saying: “The authors report on some interesting phenomena, but the ‘definitive’ interpretation and conclusion that a large impact crater underneath the ice has been discovered is a severe over-interpretation of the existing data.”[79]

See also[edit]
References[edit]
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  56. ^ Boslough M (August 2012). "Inconsistent impact hypotheses for the Younger Dryas". Proceedings of the National Academy of Sciences of the United States of America. 109 (34): E2241, author reply E2245–7. Bibcode:2012PNAS..109E2241B. doi:10.1073/pnas.1206739109. PMC 3427067. PMID 22829675.
  57. ^ Daulton TL (August 2012). "Suspect cubic diamond "impact" proxy and a suspect lonsdaleite identification". Proceedings of the National Academy of Sciences of the United States of America. 109 (34): E2242, author reply E2245–7. Bibcode:2012PNAS..109E2242D. doi:10.1073/pnas.1206253109. PMC 3427052. PMID 22829671.
  58. ^ Gill JL, Blois JL, Goring S, Marlon JR, Bartlein PJ, Nicoll K, Scott AC, Whitlock C (August 2012). "Paleoecological changes at Lake Cuitzeo were not consistent with an extraterrestrial impact". Proceedings of the National Academy of Sciences of the United States of America. 109 (34): E2243, author reply E2245–7. Bibcode:2012PNAS..109E2243G. doi:10.1073/pnas.1206196109. PMC 3427112. PMID 22829674.
  59. ^ Hardiman M, Scott AC, Collinson ME, Anderson RS (August 2012). "Inconsistent redefining of the carbon spherule "impact" proxy". Proceedings of the National Academy of Sciences of the United States of America. 109 (34): E2244, author reply E2245–7. Bibcode:2012PNAS..109E2244H. doi:10.1073/pnas.1206108109. PMC 3427080. PMID 22829672.
  60. ^ Bement LC, Madden AS, Carter BJ, Simms AR, Swindle AL, Alexander HM, Fine S, Benamara M (February 2014). "Quantifying the distribution of nanodiamonds in pre-Younger Dryas to recent age deposits along Bull Creek, Oklahoma panhandle, USA". Proceedings of the National Academy of Sciences of the United States of America. 111 (5): 1726–31. Bibcode:2014PNAS..111.1726B. doi:10.1073/pnas.1309734111. PMC 3918833. PMID 24449875.
  61. ^ Israde-Alcántara I, Bischoff JL, DeCarli PS, Domínguez-Vázquez G, Bunch TE, Firestone RB, Kennett JP, West A (2012-08-21). "Reply to Blaauw et al., Boslough, Daulton, Gill et al., and Hardiman et al.: Younger Dryas impact proxies in Lake Cuitzeo, Mexico". Proceedings of the National Academy of Sciences. 109 (34): E2245–E2247. Bibcode:2012PNAS..109E2245I. doi:10.1073/pnas.1209463109. PMC 3427057.

Apparently the wiki has been updated to include science discoveries from Chile and South Africa reported in 2019 that add considerable weight to the cosmic impact hypothesis. In addition to the black mat and/or rare metallic particle evidences, they have the extinction of large mammals and human stone tool technologies. Although clearly more research is required, I get the strong impression that the paradigm shift is now gaining irreversible momentum. I believe the influence of the Younger Dryas cataclysm on human myth, religion and history will soon be understood with new appreciation.

Here is the interesting new news:
In 2019, scientists reported evidence in sediment layers with charcoal and pollen assemblages both indicating major disturbances at Pilauco Bajo, Chile in sediments dated to 12,800 BP.[1] This included rare metallic spherules, melt glass and nanodiamonds thought to have been produced during airbursts or impacts.[1] Pilauco Bajo is the southernmost site where evidence of the Younger Dryas impacts has been reported. This has been interpreted as evidence that a strewn field from the Younger Dryas impact event may have affected at least 30% of Earth's radius.[1]

In 2019, a South African team consisting of Francis Thackeray, Louis Scott and Philip Pieterse announced the discovery of a platinum (Pt) spike in peat deposits at Wonderkrater, an artesian spring site in South Africa in the Limpopo Province, near the town of Mookgophong (formerly Naboomspruit) situated between Pretoria and Polokwane http://wiredspace.wits.ac.za/handle/10539/28129. The spike in platinum was documented in a sample dated at 12,744 cal years BP, preceding a decline in a paleo-temperature index based on multivariate analysis of pollen spectra. This drop in temperature is associated with the Younger Dryas. The Wonderkrater platinum spike is in marked contrast to the almost constant low Pt concentrations in adjacent levels. It is consistent with the Younger Dryas Impact Hypothesis and is the first of its kind in Africa, supplementing evidence for platinum anomalies at more than 25 other sites in the world. The platinum spike at the South African site has been interpreted in terms of global dispersal of platinum-rich dust at the time of the hypothesized asteroid impact, potentially associated with a crater of the kind found beneath the Hiawatha Glacier in Greenland. Thackeray and his colleagues recognise that Terminal Pleistocene megafaunal extinctions in southern Africa (Megalotragus priscus, Syncerus antiquus and Equus capensis) may be attributed 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 their study, they state that the consequences of a hypothesised YD cosmic impact (including the dispersal 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, recognising synchroneity of Pt anomalies that has been cited in support the Younger Dryas Impact Hypothesis. It is noted that in parts of South Africa, the Robberg stone tool technology terminates at about 12,800 cal yr BP, co-terminus with the termination of the Clovis technocomplex in North America, but further work is required to assess this coincidence.

https://en.wikipedia.org/wiki/Younger_Dryas_impact_hypothesis

https://www.sciencedaily.com/releases/2019/10/191002110329.htm
 

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Our modern lives on Earth are balanced on the edge of a razor. Living in cities and huge metropolitan areas, life would become unlivable within days if not hours without electricity. We are vulnerable to both man made and natural disasters which threaten the electric grid, both regionally and nationally.

Auroral records found in historical archives and cosmogenic isotopes found in natural archives have served as sound proxies of coronal mass ejections and solar energetic particles (SEPs), respectively, for dates prior to the onset of telescopic sunspot observations in 1610. These space weather events constitute a significant threat to a modern civilization, because of its increasing dependency on an electronic infrastructure. Recent studies have identified multiple extreme space weather events derived from SEPs in natural archives, such as the event in 660 BCE. While the level of solar activity around 660 BCE is of great interest, this had not been within the coverage of the hitherto-known datable auroral records in historical documents that extend back to the 6th century BCE. Therefore, we have examined Assyrian astrological reports in the 8th and 7th centuries BCE, identified three observational reports of candidate aurorae, and dated these reports to approximately 680 BCE–650 BCE. The Assyrian cuneiform tablets let us extend the history of auroral records and solar activity by a century. These cuneiform reports are considered to be the earliest datable records of candidate aurorae and they support the concept of enhanced solar activity suggested by the cosmogenic isotopes from natural archives.
https://iopscience.iop.org/article/10.3847/2041-8213/ab42e4
 

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This paper suggests extinction of species such as Neanderthal and mammoths may be related to geomagnetic excursions 40k and 12k years ago.
Reviews of Geophysics

Review Article

Open Access
The Role of Geomagnetic Field Intensity in Late Quaternary Evolution of Humans and Large Mammals
J. E. T. Channell

L. Vigliotti
First published: 29 May 2019

https://doi.org/10.1029/2018RG000629
This article was corrected on 26 July 2019. See the end of the full text for details.

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


Plain Language Summary
The strength of Earth's magnetic field in the past, recorded by rocks and sediments, provides a proxy for past flux of ultraviolet radiation (UVR) to Earth's surface due to the role of the field in modulating stratigraphic ozone. About 40,000 years ago, mammalian fossils in Australia and Eurasia record an important die‐off of large mammals that included Neanderthals in Europe. In the Americas and Europe, a large mammalian die‐off appears to have occurred ~13,000 years ago. Both die‐offs can be linked to minima in Earth's magnetic field strength implying that UVR flux variations to Earth's surface influenced mammalian evolution. For the last ~200,000 years, estimates of the timing of branching episodes in the human evolutionary tree, from modern and fossil DNA and Y chromosomes, can be linked to minima in field strength, which implies a long‐term role for UVR in human evolution. New fossil finds, improved fossil dating, knowledge of the past strength of Earth's magnetic field, and refinements in the human evolutionary tree, are sharpening the focus on a possible link between UVR arriving at the Earth's surface, magnetic field strength, and events in mammalian evolution.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018RG000629
 

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Surely some reports are false or exaggerated. But it does seem that desperation measures are currently being taken in China. Flooding by opening flood gates in dams and breaking levees around reservoirs ongoing. They are inundating farmland into wetlands or lakes in the attempt to save cities. More heavy rain is forecast thru September. Flooding of course is normal in China, but this one is said to be the worst in 100 years. There are about 94,000 dams in China, built mainly in the '50's and 60's, most of which are in bad shape. Some may be of defective design and construction.


Three Gorges Dam is a gravity dam, it was designed to hold back water by using the weight of the material alone to resist the horizontal pressure of water pushing against it. Authorities admit it is seeping, distorted and moving. Water level is said to be about 165m, with the maximum permitted by design at 175m. An earthquake, landslide or dam failure upstream could worsen its problems.

https://asiatimes.com/2020/07/three-gorges-dam-deformed-but-safe-say-operators/

https://scitechdaily.com/excessive-...dam-and-other-yangtze-river-dams-spill-water/

https://www.nationalreview.com/corner/the-risks-of-chinas-three-gorges-dams-flooding/

https://www.upi.com/Top_News/World-...s-flooding-at-Three-Gorges-Dam/2221595525864/

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Ir seems that with the last polar magnetic reversal we had the extinction of the Neanderthal. Now, with another reversal on the way, perhaps it is time for the (probably temporary) extinction of our current global technological civilization?

Below are two current articles, one form CNN and the other from Science News:

Reversal of Earth's magnetic poles may have triggered Neanderthal extinction -- and it could happen again



210219083121-restricted-file-aurora-norway-2020-exlarge-169.jpg


During this time, Earth's inhabitants would have been subjected to some dazzling displays -- northern and southern lights, caused by solar winds hitting the Earth's atmosphere, would have been frequent.
(CNN)The reversal of Earth's magnetic poles, along with a temporary breakdown of the world's magnetic field about 42,000 years ago, could have triggered a raft of environmental changes, solar storms and the extinction of the Neanderthals, according to a new study.

The Earth's magnetic field protects us, acting as a shield against the solar wind (a stream of charged particles and radiation) that flows out from the sun. But the geomagnetic field is not stable in strength and direction, and it has the ability to flip or reverse itself.
Some 42,000 years ago, in an event known as the Laschamp Excursion, the poles did just that for around 800 years, before swapping back -- but scientists were unsure exactly how or if it impacted the world.


Earth's magnetic north pole is heading for Russia and scientists are puzzled


Now, a team of researchers from Sydney's University of New South Wales and the South Australian Museum say the flip, along with changing solar winds, could have triggered an array of dramatic climate shifts leading to environmental change and mass extinctions.

Scientists analyzed the rings found in ancient New Zealand kauri trees, some which had been preserved in sediments for more than 40,000 years, to create a timescale of how Earth's atmosphere changed over time.
Using radiocarbon dating, the team studied cross sections of the trees -- whose annual growth rings served as a natural time stamp -- to track the changes in radiocarbon levels during the pole reversal.
"Using the ancient trees we could measure, and date, the spike in atmospheric radiocarbon levels caused by the collapse of Earth's magnetic field," Chris Turney, a professor at UNSW Science, director of the university's Earth and Sustainability Science Research Center and co-lead author of the study, said in a statement.
The team compared their new timescale with site records from caves, ice cores and peat bogs around the world.

'End of days'
Researchers found that the reversal led to "pronounced climate change." Their modeling showed that ice sheet and glacier growth in North America and shifts in major wind belts and tropical storm systems could be traced back to the period of the magnetic pole switch, which scientists named the "Adams Event."
"Effectively, the Earth's magnetic field almost disappeared, and it opened the planet up to all these high energy particles from outer space. It would've been an incredibly scary time, almost like the end of days," Turney said.
Researchers say the Adams Event could explain many of Earth's evolutionary mysteries, including the extinction of Neanderthals and the sudden widespread appearance of figurative art in caves worldwide.
The phenomenon would have led to some dramatic and dazzling events. In the lead-up to the Adams Event, the Earth's magnetic field dropped to only 0% to 6% of its strength, while the Sun experienced several long lasting periods of quiet solar activity.
"We essentially had no magnetic field at all -- our cosmic radiation shield was totally gone," Turney said.
The weakening of the magnetic field meant that more space weather, such as solar flares and galactic cosmic rays, could head to Earth.

"Unfiltered radiation from space ripped apart air particles in Earth's atmosphere, separating electrons and emitting light -- a process called ionisation," said Turney in a statement. "The ionised air 'fried' the Ozone layer, triggering a ripple of climate change across the globe."
During this time, Earth's inhabitants would have been subjected to some dazzling displays -- northern and southern lights, caused by solar winds hitting the Earth's atmosphere, would have been frequent. Meanwhile, the ionized air would've increased the frequency of electrical storms -- something that scientists think caused humans to seek shelter in caves.
"The common cave art motif of red ochre handprints may signal it was being used as sunscreen, a technique still used today by some groups," Alan Cooper, honorary researcher at the South Australian Museum, said in a statement.
"The amazing images created in the caves during this time have been preserved, while other art out in open areas has since eroded, making it appear that art suddenly starts 42,000 years ago," Cooper, co-lead author, added.

An upcoming reversal
In the paper, published in the journal Science, experts say there is currently rapid movement of the north magnetic pole across the Northern Hemisphere -- which could signal another reversal is on the cards.
"This speed -- alongside the weakening of Earth's magnetic field by around nine per cent in the past 170 years -- could indicate an upcoming reversal," said Cooper.
"If a similar event happened today, the consequences would be huge for modern society. Incoming cosmic radiation would destroy our electric power grids and satellite networks," he said.
Human activity has already pushed carbon in the atmosphere to levels "never seen by humanity before," Cooper said.
"A magnetic pole reversal or extreme change in Sun activity would be unprecedented climate change accelerants. We urgently need to get carbon emissions down before such a random event happens again," he added.

https://www.cnn.com/2021/02/19/world/magnetic-fields-earth-intl-scli-scn/index.html

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A magnetic field reversal 42,000 years ago may have contributed to mass extinctions
The weakening of Earth's magnetic field correlates with a cascade of environmental crises
021821_cg_pole-flip_feat-1030x580.jpg


Red ochre handprints dating to almost 42,000 years ago decorate a wall in the El Castillo cave in Spain. Red ochre has been previously suggested as an ancient form of sunscreen.

PAUL PETTITT, GOBIERNO DE CANTABRIA

By Carolyn Gramling

23 HOURS AGO

A flip-flop of Earth’s magnetic poles between 42,000 and 41,000 years ago briefly but dramatically shrank the magnetic field’s strength — and may have triggered a cascade of environmental crises on Earth, a new study suggests.

With the help of new, precise carbon dating obtained from ancient tree fossils, the researchers correlated shifts in climate patterns, large mammal extinctions and even changes in human behavior just before and during the Laschamps excursion, a brief reversal of the magnetic poles that lasted less than a thousand years. It’s the first study to directly link a magnetic pole reversal to large-scale environmental changes, the team reports in the Feb. 19 Science.

During a reversal, Earth’s protective magnetic field, which shields the planet from a barrage of charged particles streaming from the sun, can lose strength (SN: 1/28/19). So some researchers have suggested that these flip-flops may be linked to extinction events (SN: 11/19/20).

But evidence for this has proven elusive. In fact, “the general belief had been that geomagnetic changes had no impact on climate or anything else,” says Alan Cooper, an evolutionary biologist at BlueSky Genetics in Adelaide. One reason for that belief is a dearth of precise dates for the timing and duration of the geomagnetic event to correlate with environmental, ice core and magnetic rock records.

Enter New Zealand’s kauri tree, among the most ancient in the world. The country’s swampy bogs preserve the relics of kauri trees dating as far back as the Laschamps excursion. Cooper and his colleagues obtained cross-sections from four ancient trees recovered from a swamp at Ngāwhā Springs in northern New Zealand, and analyzed them for carbon-14, a radioactive form of carbon. (This is the first paper Cooper has led since he was fired from the University of Adelaide in December 2019 for misconduct, allegations which he has denied.)

021821_cg_pole-flip_inline_680.jpg

Kauri trees (one shown) have grown in New Zealand for thousands of years. By analyzing tree rings of preserved trees in the Ngawha swampland, scientists identified evidence to suggest a magnetic pole flip around 41,000 years ago.MARK MEREDITH/MOMENT/GETTY IMAGES
In particular, one massive preserved log dating to about 41,000 years ago offered up a 1,700-year-long carbon-14 record. That record revealed major changes in carbon-14 during the time period running up to and including the Laschamps excursion, the team reports. That makes sense: Increasing incoming cosmic rays — as would occur with a weakened magnetic field — also produce more carbon-14 in the atmosphere, a carbon signature which would then become incorporated into the tree’s tissues.

The team simulated how a weakened magnetic field might alter atmospheric weather patterns. The computer analysis suggested that the increase of charged particles entering the atmosphere would also increase the production of atmospheric hydrogen and nitrogen oxides — molecules that tend to consume ozone. That would reduce the ability of stratospheric ozone to shield Earth’s denizens from ultraviolet radiation. The atmospheric changes would also affect how much sunlight is absorbed at different layers in the atmosphere, leading to large-scale changes in weather patterns that would have cooled the planet.

Such effects may have in fact occurred at that time. Using the carbon-14 dates from the kauri trees, the team examined sediment, pollen, and other data from before and during the Laschamps excursion that point to sudden cooling at locations from Australia to the Andes.

Surprisingly, the most intense effects did not occur during the actual pole reversal, the team found, but in the several hundred years leading up to it, spanning about 42,300 to 41,600 years ago. During the actual reversal, the field was only about 28 percent as strong as it is today. But during that transitional period, field strength shrank to about 6 percent of its current strength. The researchers dubbed this the “Adams Transitional Geomagnetic Event” — for Douglas Adams, author of The Hitchhiker’s Guide to the Galaxy series. Adams is often associated with the number 42, said in his books to be the answer to “the ultimate question of life, the universe, and everything.”

Scientists have long debated whether climate change or human hunters were more to blame for extinction events that wiped such giant mammals as woolly mammoths and Diprotodon, a kind of super-sized Australian wombat. “It was actually one of the motivators for this study,” says study coauthor Chris Turney, a paleoclimatologist at the University of New South Wales in Sydney.

In a 2015 study by Cooper, Turney and colleagues, “we noticed that some of the megafaunal extinctions appear to cluster, and we started asking why,” Turney says (SN: 7/23/15). One such cluster of Australian megafauna extinctions, including the demise of Diprotodon and the giant kangaroo Procoptodon goliah, occurred around 42,000 years ago.

The team compared the dates of the magnetic event with previous records from ice cores that can reflect changes in solar activity. These data suggested the solar activity was at a minimum at the time. The combination of a weak magnetic field and this decrease in the sun’s output around the same time “created the perfect storm” of climate and broader environmental changes, placing a major stress on megafauna populations, Turney says. Those factors may also have led to increased competition between megafauna and human populations, as well as with Neandertals, he says.

Another possible line of evidence for a diminished ozone layer: an increasing abundance of red ochre handprints made by humans in cave paintings, the researchers note. Red ochre is thought to have been used as a sunscreen (SN: 7/3/20). There may also have been increasing use of caves between about 42,000 and 40,000 years ago, possibly as shelter from the more intense sun, the researchers report.

This is the first study to consider such a broad range of environmental consequences of extreme magnetic field changes, says Monika Korte, a geomagnetist at the GFZ German Research Centre for Geosciences in Potsdam. “The suggested links seem conceivable to me,” Korte says. But, she adds, “the biggest value of the paper is that it’s putting out several ideas that should be investigated further.”

Whether other magnetic reversals may have prompted similar upheavals in the past remains unknown, but “we hope the community will look at biological and archaeological datasets through this different lens,” Turney says. Improving the precision of isotopic dating for these events will be key — and radiocarbon dates gleaned from the New Zealand kauri trees may be able to help with other recent reversals, such as a brief reversal event called the Mono Lake Excursion that occurred about 34,000 years ago.

What long-term environmental havoc may have been wreaked by much longer reversal events recorded in ancient rocks, such the 20,000-year-long Brunhes-Matuyama reversal that began 781,000 years ago, is an even more tantalizing question, Cooper says. “The impacts may have been enormous.”

https://www.sciencenews.org/article...-reversal-mass-extinctions-environment-crisis


edit: The Guardian reports: https://www.theguardian.com/science...-flip-of-earths-magnetic-poles-study-suggests
 
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