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Evidence record

Did a comet hit at the end of the ice age?

Every sentence on the exploration belongs to at least one claim below. Each says what kind of statement it is, what it rests on, what the evidence does not establish, and how far it was checked. Nothing here is a score, and none of it is a verdict on a belief or a theory.

Last checked 24 September 2026.

  • A judgement, not a fact: 14
  • Partly checked: 19
  • Source checked: 6
  • Presented as open: 1

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.

What the question takes for granted

A question in the earth sciences about the cause of a real climate event, and about how a contested hypothesis is tested. The cold is established; the impact is disputed between a small group of proponents and a large body of critics, and the mainstream alternative has open parts of its own.

  • There was an abrupt cold period at the end of the last ice age

    Established

    The Younger Dryas is dated in ice cores and cave deposits to within decades. Its cooling was severe at high northern latitudes; elsewhere the climate shifted in other ways, and Antarctica warmed.

  • Something from space struck or exploded over the Earth at that moment

    Contested

    The question names a comet; the 2007 paper proposed one or more extraterrestrial objects without settling what they were. Its proponents say the evidence has been replicated many times; a large review and independent laboratories say the markers are neither reproducible nor unique to an impact, and no crater of that age is known.

  • One cause explains the cooling, the extinctions and the change in how people lived

    Contested

    The impact hypothesis ties them to one event. Its critics argue that the processes it explains varied in space and time and do not need a single cause.

How the question is labelled

Claim: A claim that will not settle

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s own title. It follows from claims 7 and 36: the review said the hypothesis should be rejected, and its proponents rejected the review.

Claim 1 · checked 24 September 2026 · AI-assisted audit

Claim: Younger Dryas

Kind
Framing. Signposting. It asserts nothing a source could check.

The question

Claim: The proposal has been made, challenged, defended and remade for nearly twenty years,

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Nineteen years, from the 2007 paper to this page. The papers of each side were read as abstracts; the sequence is what they carry.

Corrected

24 September 2026. Previously: “The proposal has been made, defended, refuted and remade for nearly twenty years,” Refutation is what the 2023 review claims and its proponents reject in the same journal (Sweatman and others 2024). The subtitle stated it as a settled step in the sequence.

Claim 3 · checked 24 September 2026 · AI-assisted audit

Claim: which is worth watching as an example of how such a thing goes.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s framing of why the dispute is worth reading, not a finding.

Claim 4 · checked 24 September 2026 · AI-assisted audit

Claim: In 2007 a group proposed that an airburst or impact 12,900 years ago contributed to an abrupt cold period, the extinction of North American megafauna and changes in human behaviour at the end of the Clovis period.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

The paper was read as its abstract. What it proposed is a hypothesis; that it was proposed is all this claim says.

Later work looked for

Crossref, 2018 on, "Younger Dryas impact hypothesis": the proposal has been restated and extended since; nothing changes what the 2007 paper proposed.

Corrected

24 September 2026. Previously: “In 2007 a group proposed that an airburst or impact 12,900 years ago contributed to an abrupt cold period, the extinction of North American megafauna and the end of a culture.” The paper proposes that the event contributed to “rapid human behavioral shifts at the end of the Clovis Period” and “adaptive shifts among PaleoAmericans”, not to the end of the culture.

Claim 5 · checked 24 September 2026 · AI-assisted audit

Claim: A 2023 review of the evidence concluded the hypothesis should be rejected.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Comprehensive refutation of the Younger Dryas Impact Hypothesisabstract, last sentences

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Review of the field

    The source reads: In this comprehensive review of the available evidence, we address and draw attention to these critical failings. We demonstrate that research in numerous fields has shown the YDIH should be rejected.

What this does not establish

One review, by thirteen authors, and a party to the dispute. It was read as its abstract.

Later work looked for

Crossref, 2023 on, "Holliday refutation Younger Dryas": the proponents’ reply (Sweatman and others 2024) and the review authors’ rebuttal (Holliday and others 2024); the page now reports both.

Corrected

24 September 2026. Previously: “A 2023 review went through every line of evidence and concluded the hypothesis should be rejected.” The abstract calls it a “comprehensive review of the available evidence”; that it went through every line of evidence could not be checked from what was readable.

Claim 6 · checked 24 September 2026 · AI-assisted audit

Claim: Its proponents rejected the review,

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

The reply was read as its abstract.

Later work looked for

Found by the currency search for claim 6; nothing later found that withdraws it.

Corrected

24 September 2026. Previously: “The original proponents continue to publish.” The summary did not say that the review was answered. Sweatman, Powell and West replied in Earth-Science Reviews in 2024 rejecting it; the page now says so.

Claim 7 · checked 24 September 2026 · AI-assisted audit

Claim: and continue to publish.

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Source checked. The cited passage was read, and it says this.

Claim 8 · checked 24 September 2026 · AI-assisted audit

Claim: The Younger Dryas is real: an abrupt return to severe cold in the far north, beginning about 12,900 years ago and lasting more than a thousand years,

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Timing and structure of the Younger Dryas event and its underlying climate dynamicsSignificance; abstract; Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement

    The source reads: The Younger Dryas (YD) was an ∼1,300-y period of extreme climate ... severe cooling at high northern latitudes that abruptly punctuated the warming trend ... the onsets of YD in the North Atlantic (12,870 ± 30 B.P.)

What this does not establish

Years before present, where present is 1950. The severe cooling was at high northern latitudes.

Later work looked for

Crossref, 2020 on, "Younger Dryas onset timing": nothing found that moves the onset from about 12,900 years ago.

Corrected

24 September 2026. Previously: “The Younger Dryas is real: a return to near-glacial cold, beginning abruptly about 12,900 years ago and lasting more than a thousand years, recorded in ice cores and sediments worldwide.” The cold was not worldwide. Cheng and others (2020) describe severe cooling at high northern latitudes and diverse hydroclimate shifts elsewhere, with Antarctica warming; the sentence now says where the cold was and what the rest of the world records.

Claim 9 · checked 24 September 2026 · AI-assisted audit

Claim: with shifts in climate recorded in ice cores, cave deposits and lake sediments around the world.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Timing and structure of the Younger Dryas event and its underlying climate dynamicsabstract; Significance; Results

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement

    The source reads: characterized by diverse hydroclimate shifts globally ... we used a combination of well-dated speleothem and ice-core records to pinpoint the timing of its onsets and terminations in various climatic regimes around the world ... varved lacustrine sediments of Meerfelder Maar, Germany

What this does not establish

Recorded worldwide is not the same as cold worldwide: the same paper finds the event reaching Antarctica as a warming.

Later work looked for

Covered by the search for claim 9.

Claim 10 · checked 24 September 2026 · AI-assisted audit

Claim: What caused it is the question.

Kind
Open question. Something the page says is not known.
Review
Presented as open. The page says this is unresolved, and the review found that it is.

Claim 11 · checked 24 September 2026 · AI-assisted audit

Claim: The mainstream account is a disruption of ocean circulation by meltwater.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Oceaneditor’s summary

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Observational study: associations, not causes

    The source reads: It is generally thought that an injection of freshwater from the retreating Laurentide Ice Sheet altered the Atlantic Meridional Overturning Circulation and triggered the Younger Dryas

  • Supports

    Deglacial floods in the Beaufort Sea preceded Younger Dryas coolingabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Measurement

    The source reads: the event is thought to have resulted from a slowdown of the Atlantic meridional overturning circulation in response to a sudden flood of Laurentide Ice Sheet meltwater that reached the Nordic Seas

What this does not establish

Carried by how two research papers describe their field, read as abstracts, rather than by a review of the field.

Claim 12 · checked 24 September 2026 · AI-assisted audit

Claim: The impact hypothesis is an alternative,

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Comprehensive refutation of the Younger Dryas Impact Hypothesisabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Review of the field

    The source reads: A series of publications purport to provide evidence that the Earth was subjected to an extraterrestrial event or events at ~12.9 ka creating an environmental cataclysm and the onset of the Younger Dryas stadial.

What this does not establish

Read as the review’s abstract.

Corrected

24 September 2026. Previously: “The impact hypothesis is the alternative,” The wording made it the only alternative, which none of the cited sources says.

Claim 13 · checked 24 September 2026 · AI-assisted audit

Claim: and its career is instructive.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s reason for telling the history, set out in claims 36 to 40.

Claim 14 · checked 24 September 2026 · AI-assisted audit

The claim and the test

Claim: The claim and the test

Kind
Framing. Signposting. It asserts nothing a source could check.

The claim, as made

Claim: The claim, as made

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: A 2007 paper reported a layer at the onset of the Younger Dryas containing magnetic grains with iridium, microspherules, charcoal, soot and nanodiamonds, at sites across North America.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas coolingabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Observational study: associations, not causes

    The source reads: Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds

  • Qualifies

    An independent evaluation of the Younger Dryas extraterrestrial impact hypothesisabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Observational study: associations, not causes

    The source reads: we report the results of an independent analysis of magnetic minerals and microspherules from seven sites of similar age, including two examined by Firestone et al. We were unable to reproduce any results of the Firestone et al. study

What this does not establish

What the paper reported, not what the layer contains: an independent team sampling seven sites, two of them the paper’s own, could not reproduce its magnetic grains and microspherules. Both papers were read as abstracts; the publishers’ and PubMed Central’s copies refuse this environment.

Claim 17 · checked 24 September 2026 · AI-assisted audit

Claim: The authors proposed one or more extraterrestrial objects exploding over northern North America, partially destabilising the ice sheet and triggering the cooling, with the shock wave, the heat and the fires that followed contributing to the megafaunal extinctions and to changes in how people lived at the end of the Clovis period.

Kind
Hypothesis. A proposed explanation, not an established one.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas coolingabstract, last two sentences

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Observational study: associations, not causes

    The source reads: We propose that one or more ... ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans

What this does not establish

A proposal, stated as the authors made it. The page’s next section reports how it has fared. Read as the abstract; the body was not read.

Corrected

24 September 2026. Previously: “The authors proposed one or more extraterrestrial objects exploding over or striking the ice sheet, setting off biomass burning and abrupt environmental changes which they said contributed to the cooling, the megafaunal extinctions and the end of the Clovis culture together.” The abstract proposes objects that “exploded over northern North America”, not ones striking the ice sheet, and effects contributing to “adaptive shifts among PaleoAmericans”, not the end of the Clovis culture.

Claim 18 · checked 24 September 2026 · AI-assisted audit

The review, as published

Claim: The review, as published

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: A 2023 review in Earth-Science Reviews examined the claimed markers and reported irreproducible observations, that very few sites with high levels of any claimed marker are dated accurately and precisely to 12,900 years ago, and that most of the markers are associated with terrestrial processes not unique to impacts.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Comprehensive refutation of the Younger Dryas Impact Hypothesisabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Review of the field

    The source reads: most are associated with terrestrial processes not uniquely associated with impacts or periods of abrupt climate change. Very few sites with high levels of any of the purported indicators have accurate and high-precision dating to 12.9 ka ... irreproducible observations

  • Cuts against

    Rejection of Holliday et al.’s alleged refutation of the Younger Dryas impact hypothesisabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Review of the field

    The source reads: have corroborated the YDIH and replicated the key evidence dozens of times

What this does not establish

What the review reported, from its abstract. The body, which carries the site-by-site argument, was not read.

Other readings

The proponents reply that the key evidence has been replicated dozens of times and that the review offers no new evidence of its own (Sweatman, Powell and West, 2024).

Later work looked for

Covered by the search for claim 6.

Corrected

24 September 2026. Previously: “A 2023 review in Earth-Science Reviews went through each claimed marker and reported irreproducible observations, that very few sites with high levels of any claimed marker are dated accurately and precisely to 12,900 years ago, and that most of the markers are associated with ordinary terrestrial processes not unique to impacts.” That it went through each marker could not be checked from the abstract, which names several “to name a few”; “ordinary” was the page’s gloss on the review’s words.

Claim 20 · checked 24 September 2026 · AI-assisted audit

Claim: It also reported no support for the basic premise that human populations were diminished, or that individual megafaunal species went extinct, because of a catastrophe at that moment.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Comprehensive refutation of the Younger Dryas Impact Hypothesisabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Review of the field

    The source reads: There is no support for the basic premise of the YDIH that human populations were diminished, and individual species of late Pleistocene megafauna became extinct or were diminished due to catastrophe.

What this does not establish

Read as the review’s abstract.

Claim 21 · checked 24 September 2026 · AI-assisted audit

Claim: Its title is a refutation rather than a review, which is itself a statement about how the exchange has gone.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s reading of the review’s title.

Claim 22 · checked 24 September 2026 · AI-assisted audit

Claim: How a claim like this is tested

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: A distinctive layer reported at many sites.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Reported, which is the point of the row: whether it is one layer is what is tested. Read as the abstract.

Claim 24 · checked 24 September 2026 · AI-assisted audit

Claim: Either a single event, or a set of local processes being read as one thing.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The two readings of claim 24 that the rest of the page weighs.

Claim 25 · checked 24 September 2026 · AI-assisted audit

Claim: Independent sampling decides.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

A statement of method, not of outcome.

Claim 26 · checked 24 September 2026 · AI-assisted audit

Claim: Some laboratories cannot reproduce the key markers, though the proponents count dozens of replications.

Kind
Disputed. A contested point, where the page reports a side or the disagreement.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

All three were read as abstracts.

Other readings

The proponents count replications, many by researchers outside the original team; the critics count failures to reproduce and question how markers were identified. The page reports both.

Corrected

24 September 2026. Previously: “Other laboratories cannot reproduce the key markers.” Reproduction is itself disputed: the proponents’ 2024 reply says the key evidence has been replicated dozens of times. The row stated one side as fact.

Claim 27 · checked 24 September 2026 · AI-assisted audit

Claim: If the failures stand, the finding is about the method or the sampling rather than about the past.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The inference that follows from claim 27, conditional on it.

Corrected

24 September 2026. Previously: “The finding is about the method or the sampling rather than about the past.” Made conditional, with the correction to claim 27.

Claim 28 · checked 24 September 2026 · AI-assisted audit

Claim: The proposed effects vary in time and place; the proposed cause is a single moment.

Kind
Disputed. A contested point, where the page reports a side or the disagreement.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Comprehensive refutation of the Younger Dryas Impact Hypothesisabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Review of the field

    The source reads: The YDIH invokes a cosmic event at a moment in time to explain complex processes that varied in space and time around the globe.

What this does not establish

The critics’ reading, from the review’s abstract.

Other readings

The proponents argue that the remaining differences are matters of interpretation and do not falsify the hypothesis (Sweatman, Powell and West, 2024).

Corrected

24 September 2026. Previously: “Proposed effects do not line up with their proposed cause in time.” Narrowed to what the review says: that the processes the hypothesis explains varied in space and time, not that each was shown to fall at another date.

Claim 29 · checked 24 September 2026 · AI-assisted audit

Claim: Even granting the event, the explanatory work it was invented to do is not done.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s inference from claims 21 and 29.

Other readings

The proponents hold that the event does that work; see claim 36.

Claim 30 · checked 24 September 2026 · AI-assisted audit

What remains

Claim: What remains

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: A hypothesis that explains four things at once is attractive, and that is the warning.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The four are the cooling, the extinctions, the ecological change and the change in human behaviour that the 2007 abstract ties to one event (claim 5).

Claim 32 · checked 24 September 2026 · AI-assisted audit

Why it persists

Claim: Why it persists

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: The hypothesis explains several striking things at once, which is attractive and is also the warning sign.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Restates the interlude; follows from claims 5 and 29.

Claim 34 · checked 24 September 2026 · AI-assisted audit

Claim: It has a committed group of proponents who continue to publish new sites and new markers.

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Both papers cited here were retracted in 2026 (claim 37).

Claim 35 · checked 24 September 2026 · AI-assisted audit

Claim: They replied to the review in the same journal in 2024, rejecting it, and its authors replied in turn.

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

The rebuttal was seen as a record only; its argument was not read.

Corrected

24 September 2026. Previously: “” The page reported the review and not the reply to it, which was published in the same journal; a disputed result is reported with who holds each side.

Claim 36 · checked 24 September 2026 · AI-assisted audit

Claim: In 2026 PLOS One retracted two of the group’s 2025 papers, citing problems with their dating and sampling;

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Source checked. The cited passage was read, and it says this.

Corrected

24 September 2026. Previously: “” Found by the currency search: two 2025 papers by the original proponents were retracted in February 2026, which a page about how the claim has fared should report.

Claim 37 · checked 24 September 2026 · AI-assisted audit

Claim: most of the authors who answered did not agree with the retraction.

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Of those who responded: eight of eight on one paper, eight of ten on the other. Many authors did not respond.

Claim 38 · checked 24 September 2026 · AI-assisted audit

Claim: Sustained disagreement in a literature does not always mean a question is open in the way a reader would assume.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s general point, drawn from the history in claims 35 to 38.

Claim 39 · checked 24 September 2026 · AI-assisted audit

Claim: It can also mean a claim that keeps being restated after its evidence has been examined.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s reading of this dispute. It sides with the critics, as the page does throughout.

Other readings

The proponents hold that the hypothesis is well established and that the remaining differences are ordinary scientific disagreement (Sweatman, Powell and West, 2024).

Claim 40 · checked 24 September 2026 · AI-assisted audit

What did cause the cooling

Claim: What did cause the cooling

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: The leading account remains a large release of meltwater from the retreating Laurentide Ice Sheet, weakening the Atlantic overturning circulation.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Oceanabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Observational study: associations, not causes

    The source reads: It is thought that an injection of fresh water from the retreating Laurentide Ice Sheet altered the Atlantic meridional overturning circulation and triggered the Younger Dryas

  • Supports

    Deglacial floods in the Beaufort Sea preceded Younger Dryas coolingabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Measurement

    The source reads: the event is thought to have resulted from a slowdown of the Atlantic meridional overturning circulation in response to a sudden flood of Laurentide Ice Sheet meltwater

What this does not establish

How two research papers describe the prevailing view, read as abstracts.

Corrected

24 September 2026. Previously: “The leading account remains a large release of meltwater from the retreating Laurentide Ice Sheet, weakening the Atlantic circulation that carries heat northward.” No cited source was read describing the circulation’s heat transport; the clause was cut to what the sources say.

Claim 42 · checked 24 September 2026 · AI-assisted audit

Claim: Convincing geological evidence for it was long elusive,

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Read as the abstract and editor’s summary; the paper’s body was not read.

Claim 43 · checked 24 September 2026 · AI-assisted audit

Claim: and the route has been argued about: south down the Mississippi, east through the Great Lakes, or north-west through the Mackenzie into the Arctic.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Oceaneditor’s summary; abstract, last sentence

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Observational study: associations, not causes

    The source reads: consistent with the major flood path running through the Mackenzie River into the Arctic Ocean, rather than south along the Mississippi River or east through the Great Lakes ... leads us to reject the widespread view that Agassiz overflow at this time was solely eastward into the North Atlantic Ocean

What this does not establish

Read as the abstract and editor’s summary; the paper’s body was not read.

Claim 44 · checked 24 September 2026 · AI-assisted audit

Claim: Flood gravels along the Mackenzie, reported in 2010, and a meltwater signal in Beaufort Sea sediments beginning about 12,940 years ago have favoured the north-west,

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Oceanabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Observational study: associations, not causes

    The source reads: Here we identify the missing flood path ... evident from gravels ... running through the Mackenzie River system ... we have determined the approximate age of this Mackenzie River flood into the Arctic Ocean to be shortly after 13,000 years ago, near the start of the Younger Dryas

  • Supports

    Deglacial floods in the Beaufort Sea preceded Younger Dryas coolingabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Measurement

    The source reads: the eastern Beaufort Sea contains the long-sought signal of 18O-depleted water. Beginning at ~12.94 ± 0.15 thousand years ago, ... sediment and seismic data indicate a flood of meltwater, ice and sediment to the Arctic via the Mackenzie River that lasted about 700 years.

What this does not establish

The Beaufort Sea date carries an uncertainty of about 150 years. Both papers were read as abstracts.

Later work looked for

Crossref, 2018 on, "Younger Dryas meltwater Lake Agassiz": Norris and others (2021) find the north-western outlet viable but cannot place its flood at the onset; added to the page as claim 46.

Corrected

24 September 2026. Previously: “” The page named the argument over the route and not the evidence since 2010. Added from Murton 2010 (already cited), Keigwin 2018 and Norris 2021.

Claim 45 · checked 24 September 2026 · AI-assisted audit

Claim: though a 2021 study of that outlet could not say whether its flood came near the start of the cold.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Read as the abstract. The study models the flood from the outlet’s form.

Claim 46 · checked 24 September 2026 · AI-assisted audit

Claim: So the mainstream explanation has its own unresolved part,

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from claims 43 to 46.

Claim 47 · checked 24 September 2026 · AI-assisted audit

Claim: which is a fair thing to state alongside the case against the alternative.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s judgement of balance.

Corrected

24 September 2026. Previously: “which is a fair thing to state alongside the refutation of the alternative.” The refutation is the 2023 review’s claim and is rejected by the proponents; the page now names it as a case rather than a settled result.

Claim 48 · checked 24 September 2026 · AI-assisted audit

What was read