Evidence record

Was the whole planet once frozen?

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.

Source checked: 46
A judgement, not a fact: 7
Presented as open: 2
Partly checked: 2

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.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 about the deep past that the rocks answer in part. That ice reached sea level in the tropics twice is well supported; whether the ocean froze over entirely, or kept a belt of open water, is argued between modelling and field groups, and the page reports both.

Glacial deposits formed at low latitude
Established
The question only arises because palaeomagnetism places some Cryogenian glacial deposits, grounded below sea level, in the tropics. The review the page leans on, and its critics, both start from this.
"The whole planet" means a completely frozen ocean
Contested
Ice sheets at sea level at all latitudes is not the same thing as an ocean frozen over everywhere. Waterbelt models keep open water near the equator while ice reaches the tropics on land; the page sets out both.

How the question is labelled

Claim: Ice at the equator

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: Geological evidence indicates that grounded ice sheets reached sea level at all latitudes during two long-lived Cryogenian (58 and ≥5 My) glaciations.

What this does not establish

Ice sheets reaching the equator on land is the observation. Whether the equatorial ocean also froze is the argument the page reports.

Later work looked for

Crossref, 2018 on, "Cryogenian low-latitude glaciation paleomagnetism": regional sedimentology and geochemistry, nothing that moves the deposits out of the low latitudes; nothing that changes the page.

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

Claim: Snowball

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

The question

Claim: Glacial deposits from around 700 million years ago sit in rocks that were in the tropics when they formed

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPaleogeography, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: Certain Sturtian and Marinoan deposits were formed by glaciers that were grounded below sea level at low paleomagnetic latitudes
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyGeochronology section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The onset of the Sturtian cryochron at low (21° ± 3°N) paleolatitude is tightly constrained between 717.5 and 716.3 Ma

Later work looked for

Corrected

24 September 2026. Previously: “Glacial deposits from 700 million years ago sit in rocks that were at the equator when they formed” The review places the deposits at "low paleomagnetic latitudes", the Sturtian onset at 21 degrees north, not on the equator; and the two glaciations span about 717 to 635 million years ago.

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

Claim: and the argument about what that means has run for more than thirty years.

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.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyGeochronology section, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Before 2004 (56), no Cryogenian glacial deposit had been directly dated radiometrically. The Snowball Earth hypothesis (24) was then 12 years old
Twelve years old in 2004 puts the hypothesis in 1992, thirty-four years before 2026.

What this does not establish

Thirty years dates the Snowball Earth hypothesis itself. The puzzle of low-latitude glacial deposits is older.

Corrected

24 September 2026. Previously: “has run for thirty years.” The review dates the hypothesis to 1992, twelve years before 2004, which makes the argument about thirty-four years old.

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

Claim: Twice in the Cryogenian period, glaciers reached sea level in the tropics.

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: Geological evidence indicates that grounded ice sheets reached sea level at all latitudes during two long-lived Cryogenian (58 and ≥5 My) glaciations.

Later work looked for

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

Claim: Whether the ocean froze over completely, or kept a belt of open water, is still argued,

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Sea-ice thermodynamics can determine waterbelt scenarios for Snowball Earthabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: there is an ongoing debate about how the feedback stopped: with fully ice-covered oceans or with a narrow strip of open water around the Equator.
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyWaterbelt solutions, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: There have been concerted efforts to find climate-model solutions that satisfy basic inferences from Cryogenian geology

What this does not establish

The 2017 review is by proponents of a fully frozen ocean; the 2024 paper is a modelling study that reports the debate in its introduction.

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

Claim: and the difference matters because the first version is hard to escape from and hard to survive in.

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 summary of the two difficulties it goes on to report: escape (claims 19 to 24) and survival (claims 40 and 41).

Context
Snowball Earth climate dynamics and Cryogenian geology-geobiologyWaterbelt solutions, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Some of these efforts were motivated by a perception that the “hard-snowball” hypothesis is implausible in light of the fossil record
Context
Snowfall-albedo feedbacks could have led to deglaciation of snowball Earth starting from mid-latitudesabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: a seemingly insurmountable challenge to the hard-snowball hypothesis lies in the difficulty in explaining how the planet could have exited the glaciated state within a realistic range of atmospheric carbon dioxide concentrations

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

Claim: The evidence is a rock: glacial debris dumped by ice, in a formation whose magnetic minerals show it was near the equator when it was laid down.

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 5 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: Paleocontinents South Australia (SA) and South China (SCh) are similarly fixed at 635 Ma by paleomagnetic data from the Nuccaleena Formation cap dolostone (33) and the Nantuo Formation glacial diamictite
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPaleogeography, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Certain Sturtian and Marinoan deposits were formed by glaciers that were grounded below sea level at low paleomagnetic latitudes

What this does not establish

"A rock" is a figure of speech: the evidence is many formations on several palaeocontinents.

Later work looked for

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

Claim: Explaining that requires either moving the continent or freezing the tropics, and the magnetism is fairly clear about the continent.

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 claim 8. Both sides of the argument the page reports accept the low-latitude reading of the magnetism.

Context
Sedimentary challenge to Snowball Earthabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: Evidence from the magnetic field fossilized in sedimentary rocks suggests that, more than 600 million years ago, ice occupied tropical latitudes.

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

What the rocks record

Claim: What the rocks record

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

Tropical glaciation happened, twice

Claim: Tropical glaciation happened, twice

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: Geological evidence indicates that grounded ice sheets reached sea level at all latitudes during two long-lived Cryogenian (58 and ≥5 My) glaciations.

Later work looked for

Crossref, 2018 on, "Marinoan glaciation onset age U-Pb" and "Sturtian glaciation onset duration geochronology": Nelson and others (Geology, 2020) put the Marinoan onset after 651.69 Ma, and Dutkiewicz and others (Geology, 2024) give the Sturtian as about 717 to 661 Ma; nothing that changes the page.

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

Claim: Two intervals in the Cryogenian, roughly 717 to 660 and 650 to 635 million years ago, left glacial deposits in more than ninety formations on twenty-two palaeocontinents and microcontinents, including rocks that palaeomagnetism places in the tropics.

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyTable 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: Sturtian glacial onset: 717.5 to 716.3 Ma ... Sturtian deglaciation/cap carbonate: 659.3 to 658.5 Ma ... Marinoan glacial onset: 649.9 to 639.0 Ma ... Marinoan deglaciation/cap carbonate: 636.0 to 634.7 Ma
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPaleogeography, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Cryogenian glacial deposits (28, 175) are reliably documented in >90 formations on 22 paleocontinents and microcontinents worldwide (Fig. 4).

What this does not establish

The Marinoan onset is the loosest of the four dates, between 649.9 and 639.0 million years ago in the review.

Later work looked for

Corrected

24 September 2026. Previously: “Two intervals in the Cryogenian, roughly 717 to 660 and 650 to 635 million years ago, left glacial deposits in more than ninety formations on twenty-two palaeocontinents, including rocks that palaeomagnetism places in the tropics.” The review's count of twenty-two is of 'paleocontinents and microcontinents', not palaeocontinents alone; the page now names the same whole.

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

Claim: The onset of the first and the end of both are now dated to about a million years, on several of those continents at once.

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyGeochronology section, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: Today, the onset of the Sturtian cryochron and the terminations of both cryochrons are tightly constrained at a million-year resolution by U-Pb and Re-Os geochronology on multiple paleocontinents (Table 1).

Later work looked for

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

Claim: The glacial deposits are capped, worldwide, by a distinctive layer of carbonate rock whose chemistry indicates a sudden and extreme change in the ocean and atmosphere at the end of the glaciation.

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyCap carbonates and Snowball Earth aftermaths, opening
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: are laterally continuous, meter- to decameter-thick units of lithologically distinctive carbonate (dolomite and/or limestone) that sharply overlie Cryogenian glacial deposits globally
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 23 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Distribution of Marinoan cap dolostones over 110° paleolatitude ... records an anomalous state of carbonate oversaturation in the surface ocean despite extreme CO2 acidification in the Snowball aftermath
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyWaterbelt solutions, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: to satisfy the geologically observed abrupt deglaciations and attendant geochemical anomalies
Context
A Neoproterozoic Snowball Earthabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: producing the cap carbonate rocks observed globally

Later work looked for

Crossref, 2018 on, "cap carbonate deposition duration Marinoan": studies of individual caps, nothing that changes the page.

Corrected

24 September 2026. Previously: “Each glacial deposit is capped by a distinctive layer of carbonate rock” The review says cap carbonates overlie the glacial deposits "globally", not that every deposit carries one.

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

Claim: How fast the cap itself accumulated is unresolved: its sedimentary structures suggest quickly, and the magnetism recorded in it suggests tens or hundreds of thousands of years.

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.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyTime scale for cap-carbonate transgressions
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: existing geochronology does not resolve the time scale over which they were deposited. Sedimentary structures in cap carbonates are consistent with rapid accumulation (420, 425, 440, 443), but this evidence is qualitative.
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyCap carbonates and sequence stratigraphy, on magnetostratigraphy
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: magnetostratigraphic records (428–431), where detrital hematite carries the natural remanent magnetization, imply that certain cap carbonates accumulated extremely slowly, over several 10⁴ or 10⁵ years
Notation restored: Subscript and superscripts restored from the Europe PMC full text (PMC5677351), which marks them with <sub> and <sup>, read 2026-09-24. The text as extracted reads: magnetostratigraphic records (428–431), where detrital hematite carries the natural remanent magnetization, imply that certain cap carbonates accumulated extremely slowly, over several 104 or 105 years

What this does not establish

The slow reading assumes polarity reversals then took about as long as recent ones, which the review says must now be questioned.

Claim 15 · checked 24 September 2026 · AI-assisted audit

How a snowball ends

Claim: How a snowball ends

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

Corrected

24 September 2026. Previously: “The escape mechanism is the strongest part of the theory” A ranking no source makes. The review credits the dating, "more than any other factor", with getting the hypothesis taken seriously, and a later model challenges the carbon dioxide route out.

Claim: With the surface frozen, rain stops and the weathering of rock that normally removes carbon dioxide all but stops with it.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIntroduction, quoting Walker and others (ref. 69)
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: If a global glaciation were to occur, the rate of silicate weathering should fall very nearly to zero (due to the cessation of normal processes of precipitation, erosion, and runoff)
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: there is no rain to scrub CO2 (insoluble in snow) from the atmosphere
Qualifies
Snowball Earth climate dynamics and Cryogenian geology-geobiologyGeochronology section, on CO2 sinks
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Sinks for CO2 on Snowball Earth include subglacial weathering of continental crust (171), including LIPs, low-temperature alteration of young oceanic crust on the flanks of seafloor spreading ridges

What this does not establish

Weathering under the ice and on the seafloor still takes some carbon dioxide out, which the review counts as a factor in how long the first glaciation lasted.

Corrected

24 September 2026. Previously: “the weathering of rock that normally removes carbon dioxide stops with it.” The review lists sinks that continue under the ice, subglacial weathering and seafloor alteration, and the quotation it gives says weathering falls "very nearly to zero".

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

Claim: Volcanoes keep emitting.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 1 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: With reduced sinks for carbon, normal volcanic outgassing drives atmospheric CO2 higher over millions to tens of millions of years

What this does not establish

The outgassing rate over a glaciation is assumed in the models, not measured.

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

Claim: Over millions of years carbon dioxide builds to something like a hundred times the present level,

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: Geochemical data imply that CO₂ was 10² PAL (present atmospheric level) at the younger termination, consistent with a global ice cover.
Notation restored: Superscript and subscript restored from the Europe PMC full-text XML (PMC5677351), read 2026-09-24. The text as extracted reads: Geochemical data imply that CO2 was 102 PAL (present atmospheric level) at the younger termination, consistent with a global ice cover.
10² is a hundred times the present level.
Qualifies
A Neoproterozoic Snowball Earthabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: ended abruptly when subaerial volcanic outgassing raised atmospheric carbon dioxide to about 350 times the modern level

What this does not establish

The 1998 paper estimated about 350 times the modern level; the page gives the later review’s geochemical figure of 10 squared.

Claim 19 · checked 24 September 2026 · AI-assisted audit

Claim: which is what the geochemistry at the younger termination indicates.

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: Geochemical data imply that CO₂ was 10² PAL (present atmospheric level) at the younger termination
Notation restored: Subscript and superscripts restored from the Europe PMC full text (PMC5677351), which marks them with <sub> and <sup>, read 2026-09-24. The text as extracted reads: Geochemical data imply that CO2 was 102 PAL (present atmospheric level) at the younger termination

What this does not establish

A proxy estimate for the Marinoan termination only, not a measurement for both.

Later work looked for

Crossref, 2018 on, "Cryogenian atmospheric CO2 termination snowball": no new estimate of the level at termination turned up; nothing that changes the page.

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

Claim: That eventually overwhelms the reflectivity of the ice, and the deglaciation is catastrophic: in a coupled ice-sheet model the ice line runs from the equator to the poles in about two thousand years, into extreme greenhouse warming over an ocean that has just been uncovered,

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 1 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field
The source reads: Once the tropical ocean begins to open, ice-albedo feedback drives the ice line rapidly poleward (in ~2 ky) (327) to (d), where high CO2 combined with low surface albedo creates a torrid greenhouse climate.
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyTime scale for cap-carbonate transgressions
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The time scale for Snowball deglaciation in a coupled ice-sheet–energy-balance model is ~2 ky (327).

What this does not establish

One model’s time scale, which the review judges realistic.

Corrected

24 September 2026. Previously: “in the models the ice line runs” The two-thousand-year figure comes from one coupled model the review cites.

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

Claim: which is what the cap carbonates appear to record.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: These predictions are increasingly supported by combined U-Pb and Re-Os geochronology (32, 56–65, 83) and by geochemical data
Context
A Neoproterozoic Snowball Earthabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: The rapid termination would have resulted in a warming of the snowball Earth to extreme greenhouse conditions.

What this does not establish

This is the snowball reading of the cap carbonates, by its proponents. How fast the caps accumulated is unresolved (claim 15).

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

Claim: The loop this describes is what makes the idea testable.

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 the predictions in claim 24.

Context
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 1 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The hysteresis loop predicts that Snowball glaciations were long-lived (b and c), began synchronously at low latitudes (a and b), and ended synchronously at all latitudes under extreme CO2 radiative forcing (c and d).

Claim 23 · checked 24 September 2026 · AI-assisted audit

Claim: It predicts glaciations that were long, that began at low latitude, and that ended everywhere at once under extreme carbon dioxide forcing,

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 1 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: The hysteresis loop predicts that Snowball glaciations were long-lived (b and c), began synchronously at low latitudes (a and b), and ended synchronously at all latitudes under extreme CO2 radiative forcing (c and d).

What this does not establish

A prediction of the model, not an observation.

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

Claim: which the dating and the geochemistry have increasingly supported since.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: These predictions are increasingly supported by combined U-Pb and Re-Os geochronology (32, 56–65, 83) and by geochemical data

What this does not establish

The review’s own assessment; its authors are the hypothesis’s leading proponents.

Corrected

24 September 2026. Previously: “which is what the dating has since found.” The dating bears on timing, the geochemistry on carbon dioxide, and the review says "increasingly supported", not found.

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

Claim: The threshold is a model estimate, and the estimates span a factor of ten.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIntroduction, on the deglaciation threshold
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field
The source reads: Current estimates of the CO2 level required for Cryogenian Snowball termination range from 0.01 to 0.1 volume mixing ratio, dependent on the tropical ice albedo and other factors

What this does not establish

The range depends mostly on how reflective the tropical ice is assumed to be.

Corrected

24 September 2026. Previously: “” The page presented the carbon dioxide route out without saying that the level required is uncertain by a factor of ten in the review it cites.

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

Claim: One Earth system model starts the thaw in the mid-latitudes instead, with dust darkening the snow, even at present-day carbon dioxide.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowfall-albedo feedbacks could have led to deglaciation of snowball Earth starting from mid-latitudesabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: deglaciation is not initiated in the tropics ... Instead, comparatively low precipitation rates in the mid-latitudes in combination with high maximum temperatures facilitate lower albedos and snow dynamics that – for extreme dust fluxes – trigger deglaciation even at present-day carbon dioxide levels.
Supports
Snowfall-albedo feedbacks could have led to deglaciation of snowball Earth starting from mid-latitudesResults, snow dynamics in the extratropics; Fig. 6
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: the simulated snow dynamics in the extratropics ... allow for deglaciation ... and for extreme dust deposition rates snow and ice melt are simulated even at present-day pCO2s
“Extreme” here is a dust flux ten times the present-day global mean, per the same section.

What this does not establish

One model, and only for extreme dust fluxes. It does not show that this is how either glaciation ended.

Corrected

24 September 2026. Previously: “” A published challenge to the escape mechanism the page describes, which the page did not mention.

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

Claim: In and out of a snowball

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

Claim: Runaway freezing

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 1 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: whereupon the ice line advances uncontrollably to the equator

What this does not establish

What the model does; the process itself is inferred, not observed.

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

Claim: Ice reflects sunlight, which cools the planet, which makes more ice.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIntroduction, first sentence
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: For 50 years, climate models of increasing complexity have hinted that Earth is potentially vulnerable to global glaciation through ice-albedo feedback

What this does not establish

The feedback is physics; its runaway to the equator is a model result.

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

Claim: Past a critical latitude the feedback runs to the equator.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologySea-glacier development on the Snowball ocean
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: A Snowball Earth ensues when sea ice, having reached a critical latitude, advances uncontrollably to the equator through ice-albedo feedback

What this does not establish

Where the critical latitude lies differs between models.

Claim 31 · checked 24 September 2026 · AI-assisted audit

Claim: The silicate weathering thermostat stalls

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIntroduction, quoting Walker and others (ref. 69)
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: If a global glaciation were to occur, the rate of silicate weathering should fall very nearly to zero

What this does not establish

Weathering under the ice and on the seafloor continues at a lower rate.

Corrected

24 September 2026. Previously: “The silicate weathering thermostat stops” The source says weathering falls very nearly to zero, and lists sinks that continue under the ice.

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

Claim: With no rain, weathering falls almost to zero, so the process that normally removes volcanic carbon dioxide is all but switched off.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIntroduction, quoting Walker and others (ref. 69)
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: the rate of silicate weathering should fall very nearly to zero (due to the cessation of normal processes of precipitation, erosion, and runoff), and carbon dioxide should accumulate in the atmosphere at whatever rate it is released from volcanoes

What this does not establish

Weathering under the ice and on the seafloor continues at a lower rate.

Corrected

24 September 2026. Previously: “No liquid water means no weathering, so the process that normally removes volcanic carbon dioxide is switched off.” There is liquid water on a snowball (the ocean under the ice, meltwater ponds) and weathering continues under the ice and on the seafloor; the source says it falls very nearly to zero for want of rain and runoff.

Claim 33 · checked 24 September 2026 · AI-assisted audit

Claim: Carbon dioxide accumulates for millions of years

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 1 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: normal volcanic outgassing drives atmospheric CO2 higher over millions to tens of millions of years

What this does not establish

The durations themselves are dated (claim 12); the accumulation is modelled.

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

Claim: Volcanoes continue.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 1 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: With reduced sinks for carbon, normal volcanic outgassing drives atmospheric CO2 higher

What this does not establish

The outgassing rate over a glaciation is assumed in the models, not measured.

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

Claim: The atmosphere builds towards concentrations that can overcome the ice.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 1 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: drives atmospheric CO2 higher over millions to tens of millions of years (73) until it reaches the deglaciation threshold

What this does not establish

How high the threshold is remains uncertain by a factor of ten (claim 26).

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

Claim: Sudden deglaciation

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 1 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field
The source reads: Once the tropical ocean begins to open, ice-albedo feedback drives the ice line rapidly poleward (in ~2 ky)

What this does not establish

Abrupt deglaciation is also what the rocks record; the time scale is a model’s.

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

Claim: The ice retreats quickly into an atmosphere with an extreme greenhouse, and the cap carbonates are deposited in the aftermath.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 1 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field
The source reads: where high CO2 combined with low surface albedo creates a torrid greenhouse climate
Context
A Neoproterozoic Snowball Earthabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: The transfer of atmospheric carbon dioxide to the ocean would result in the rapid precipitation of calcium carbonate in warm surface waters, producing the cap carbonate rocks observed globally.

What this does not establish

How long the caps took to accumulate is unresolved (claim 15).

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

How complete the ice was

Claim: How complete the ice was

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

Claim: A planet that freezes this thoroughly is difficult to thaw,

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 1 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: normal volcanic outgassing drives atmospheric CO2 higher over millions to tens of millions of years (73) until it reaches the deglaciation threshold

What this does not establish

The hysteresis is a model property; how much carbon dioxide it takes is uncertain (claim 26).

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

Claim: which is why the escape route is the part that had to work.

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 review records that a global glaciation became thinkable once it was shown it could end; the page’s line follows from that.

Context
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The recognition that a panglacial state might be self-terminating (69), due to feedback in the geochemical carbon cycle, meant that its occurrence in the geological past could not be ruled out on grounds of irreversibility.

Claim 41 · checked 24 September 2026 · AI-assisted audit

Hard snowball or slushball

Claim: Hard snowball or slushball

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

The review calls the open-water solutions "Waterbelt" and says "slushball" names them less accurately; the heading uses the familiar word.

Claim: A completely frozen ocean is difficult to reconcile with the survival of photosynthetic life,

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyWaterbelt solutions, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Some of these efforts were motivated by a perception that the “hard-snowball” hypothesis is implausible in light of the fossil record
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyOceanic ice and the evolution of Cryogenian marine life, opening
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: it is difficult to maintain areas of oceanic ice sufficiently thin for sub-ice phototrophy, <20 m of clear ice, particularly in the coldest early part of a cryochron
Context
Sea-ice thermodynamics can determine waterbelt scenarios for Snowball Earthabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: they provide a refugium for the survival of photosynthetic aquatic life, while still explaining Neoproterozoic geology

Claim: which came through these intervals and diversified afterwards.

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPre-Sturtian and Cryogenian fossil record
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: After the Cryogenian ended, acritarch diversity increased sharply (316, 317), as perhaps did that of benthic macroalgae ... multiple clades of eukaryotic algae and heterotrophs, both single-celled and multicellular, not only survived the Cryogenian glaciations but may have significantly evolved during that period

What this does not establish

The review calls the fossil record too coarse to tie extinctions or originations to particular glaciations.

Later work looked for

Crossref, 2018 on, "snowball Earth animal evolution oxygen Cryogenian": work on possible refuges and snow algae; nothing that changes the page.

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

Claim: Refuges have been proposed: thin ice in the tropics, meltwater ponds on the surface, cracks and volcanic areas.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyOceanic ice and the evolution of Cryogenian marine life, opening
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The most favorable conditions for thin oceanic ice exist in hydrothermal areas (289) and marine embayments into low-albedo ice-free land areas
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyOceanic ice and the evolution of Cryogenian marine life, opening, on cryoconite ponds
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: would have provided refugia for the survival, growth and evolution of a variety of organisms, including multicellular eukaryotes.
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyGrounding-line crack systems
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Brine inclusions in modern sea ice provide habitats for prokaryotic and eukaryotic phototrophs (mainly diatoms)
Qualifies
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 17 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: cracks were deeply recessed, weakly illuminated, and more important as conduits for air-sea gas exchange than for phototrophy.

What this does not establish

Proposed, not found: there is no fossil record from any of these settings, and the review judges cracks poor places for photosynthesis.

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

Claim: The alternative is that a belt of open water survived near the equator throughout,

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyWaterbelt solutions, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field
The source reads: while maintaining a finite zone of open water in the warmest area

Claim: which preserves the biology at the cost of weakening the escape mechanism.

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.

Open water gives a refuge; the review finds the hysteresis that makes the exit abrupt smaller in the open-water states it discusses.

Context
Snowball Earth climate dynamics and Cryogenian geology-geobiologyWaterbelt solutions, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Second, a large hysteresis must exist between the Waterbelt and nonglacial states (116) to satisfy the geologically observed abrupt deglaciations
Context
Snowball Earth climate dynamics and Cryogenian geology-geobiologyWaterbelt solutions, on Jormungand states
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Strong hysteresis between Jormungand and nonglacial states has been found in aquaplanet atmosphere-only GCMs, although less so than for the Snowball state

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

Claim: These solutions have to sit next to the runaway without falling into it for millions of years, and still leave the abrupt deglaciation the cap carbonates record.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyWaterbelt solutions, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the solutions, by their nature, lie close to the Snowball bifurcation (Fig. 1), yet they must resist falling irrevocably into the Snowball state for millions to tens of millions of years
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyWaterbelt solutions, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: a large hysteresis must exist between the Waterbelt and nonglacial states (116) to satisfy the geologically observed abrupt deglaciations

What this does not establish

These requirements are set out by proponents of the hard snowball, in the review the page cites.

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

Claim: Whether they can depends on the model: in one, a fuller treatment of sea ice leaves no stable belt of open water at all.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Sea-ice thermodynamics can determine waterbelt scenarios for Snowball Earthabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: Including heat capacity by using the three-layer Winton model increases snow cover and enhances the ice–albedo feedback. The waterbelt hysteresis found for the zero-layer model disappears in the three-layer model, and no stable waterbelt states are found.
Supports
Sea-ice thermodynamics can determine waterbelt scenarios for Snowball Earthsection 4, Conclusions
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Model
The source reads: The main finding of our work is that stable waterbelt states are possible and accessible in the zero-layer Semtner model but not in the three-layer Winton model.

What this does not establish

One idealised model with no continents (an aquaplanet); other models do find stable open-water states.

Corrected

24 September 2026. Previously: “” Later modelling (Hörner and Voigt 2024) bears directly on whether open-water solutions are stable; the page now says so.

Claim 49 · checked 24 September 2026 · AI-assisted audit

Claim: The sediments are read both ways.

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
Sedimentary challenge to Snowball Earthabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: The sedimentary evidence therefore indicates that despite the severity of glaciation, some oceans must have remained ice-free.
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyCryoconite flushing and volcanic ash deposition
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: It has been argued that the deposition of these layers indicates ice-free conditions (83). But what if the ash was deposited first on ice and then glacially advected to the low-latitude sublimation surface of the sea glacier

What this does not establish

Allen and Etienne was read as its abstract.

Corrected

24 September 2026. Previously: “The sediments are read both ways: layers of volcanic ash inside the glacial deposits have been argued to require open water, and argued to have been carried to the tropics by the ice itself.” The page’s only source for the open-water side was a review by hard-snowball proponents. The standard sedimentary case for open water, Allen and Etienne 2008, is now named and cited.

Claim 50 · checked 24 September 2026 · AI-assisted audit

Claim: Allen and Etienne argue that glaciers kept delivering sediment to open ocean throughout, so some ocean stayed free of ice.

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
Sedimentary challenge to Snowball Earthabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: sedimentary rocks deposited during these cold intervals indicate that dynamic glaciers and ice streams continued to deliver large amounts of sediment to open oceans throughout the glacial cycle. The sedimentary evidence therefore indicates that despite the severity of glaciation, some oceans must have remained ice-free.

What this does not establish

Read as its abstract. The 2017 review, from the other side, argues that ice flowing into the tropics could carry sediment without open water.

Claim 51 · checked 24 September 2026 · AI-assisted audit

Claim: Layers of volcanic ash inside the glacial deposits have been argued to require open water, and argued to have been carried to the tropics by the ice itself.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyCryoconite flushing and volcanic ash deposition
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Discrete layers of volcanic ash ... are occasionally found within stratified glaciomarine deposits ... It has been argued that the deposition of these layers indicates ice-free conditions (83). But what if the ash was deposited first on ice and then glacially advected to the low-latitude sublimation surface of the sea glacier

Claim 52 · checked 24 September 2026 · AI-assisted audit

What started it

Claim: What started it

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

Claim: Candidates include the weathering of a large volcanic province emplaced in the deep tropics, the breakup of a supercontinent bringing rain to its dry interior, and sulphur from that same province loading the stratosphere with reflective aerosol.

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPaleogeography, on the Franklin LIP
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: The last one was emplaced squarely across the paleoequator (34, 35, 127, 191). Weathering of basaltic rock consumes CO2 more rapidly than weathering average upper continental crust
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPaleogeography
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the breakup of the Rodinia supercontinent at this time. The breakup presumably reduced CO2 greenhouse warming in two ways. First, moistening of previously arid lands in the supercontinental interior adjusted CO2 to a lower level because of increased weathering efficiency
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPaleogeography, on sulfate aerosol
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Sulfate aerosol increases the planetary albedo, and the resultant cooling effect is maximized if injection occurs at low latitudes, where insolation is strongest
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPaleogeography, on sulfate aerosol
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Accordingly, the Franklin LIP had unique climatic consequences because S-rich lavas were erupted at high rates at the paleoequator in an already-cold climate.

Claim: The Sun was about six per cent fainter than it is now,

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIce-sheet stability and extent under precession-like forcing and variable CO2, model set-up
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · A simulation · Review of the field
The source reads: 94% of present solar luminosity

What this does not establish

The figure is the solar luminosity the review’s climate models are run at, not a measurement.

Claim 55 · checked 24 September 2026 · AI-assisted audit

Claim: which is a condition rather than a trigger.

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: a Sun fainter for the whole era cannot explain why glaciation began when it did.

Claim 56 · checked 24 September 2026 · AI-assisted audit

Claim: The first two would have drawn carbon dioxide down and moved the climate towards the threshold.

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPaleogeography, on pre-Sturtian weathering
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: Enhanced CO2 consumption and global cooling due to the breakup of the Rodinia supercontinent and the emplacement of a temporal cluster of LIPs (174, 186, 196, 199) purportedly moved the climate system closer to the Snowball bifurcation

What this does not establish

The review itself says "purportedly".

Claim 57 · checked 24 September 2026 · AI-assisted audit

Claim: The province and the glacial onset are indistinguishable in time,

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyGeochronology section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: The Sturtian onset is indistinguishable in time from the most reliable U-Pb baddeleyite ages of 716.33 ± 0.54 Ma (32) and 716 ± 1 Ma (127) from mafic sills and dikes in different parts of the Franklin LIP

Later work looked for

Claim 58 · checked 24 September 2026 · AI-assisted audit

Claim: which is suggestive and does not settle which of the mechanisms it supplied did the work.

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.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPaleogeography, on the Franklin LIP
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The synchroneity of Franklin LIP emplacement with the onset of low-latitude glaciation (32) raises the possibility that volcanism was the proximal trigger for the Sturtian cryochron

Claim 59 · checked 24 September 2026 · AI-assisted audit

What may have followed from it

Claim: What may have followed from it

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

That it made animals possible

Claim: That it made animals possible

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

Names the possibility the passage examines; the passage says the link is not established.

Claim: Animal body fossils appear in the record after the second of these glaciations.

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
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 23 caption, panel H, basal Doushantuo Formation
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Review of the field
The source reads: Tianzhushania spinosa arrow indicates the first appearance of chert nodules preserving diapause cysts containing eggs and embryos of stem-group metazoans
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the younger tandem (Fig. 2A) was associated with the emergence of multicellularity in animals

What this does not establish

Earlier animal body fossils have been claimed and are not accepted by the review; molecular evidence puts the lineage earlier (claim 63).

Later work looked for

Crossref, 2016 on, "Gaskiers Ediacaran biota first appearance": Pu and others (Geology, 2016) date the first large Ediacaran fossils to within 9.5 million years after about 580 million years ago, long after the second glaciation; nothing that changes the page.

Claim 62 · checked 24 September 2026 · AI-assisted audit

Claim: Molecular clocks put the lineage earlier, before the first of them, and disputed biomarkers place sponges in the warm interval between the two.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPre-Sturtian and Cryogenian fossil record
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Molecular clocks predict that stem-group metazoans predated the Sturtian cryochron (47), and sterane biomarkers suggest that a metazoan crown group, demosponges, evolved before the Marinoan cryochron [(46–48); but see the study by Brocks and Butterfield (314)].
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyFig. 3 caption
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Sterane biomarkers in the South Oman Salt Basin are interpreted to be products of demosponges, appearing no later than the clement interlude between the Sturtian and Marinoan glaciations

What this does not establish

The review notes that weak pre-Cambrian calibration compromises the molecular clock estimates.

Claim 63 · checked 24 September 2026 · AI-assisted audit

Claim: On that reading the animals came through the ice rather than after it.

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 claim 63, and holds only as far as the molecular clocks and biomarkers do.

Claim 64 · checked 24 September 2026 · AI-assisted audit

Claim: The glaciations are associated with the emergence of animals, and a causal link is not established.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the younger tandem (Fig. 2A) was associated with the emergence of multicellularity in animals
Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyPre-Sturtian and Cryogenian fossil record
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The fossil record in total is too coarse to correlate extinctions or originations with cryochrons

Corrected

24 September 2026. Previously: “A causal link is frequently proposed and not established.” No source read says the link is "frequently proposed". The review states the association and that the fossil record cannot tie originations to the glaciations.

Claim 65 · checked 24 September 2026 · AI-assisted audit

Claim: The oxygen record between 800 and 400 million years ago is not good enough to defend or refute the idea that these glaciations pushed the atmosphere towards its later state.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Snowball Earth climate dynamics and Cryogenian geology-geobiologyMeltwater flushing, the carbon cycle, and atmospheric oxygen
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the existing record of atmospheric oxygenation between 0.8 and 0.4 Ga overall remains inadequate to confidently defend or refute the hypothesis (356) that Cryogenian glaciation drove atmospheric O2 irreversibly from a Proterozoic to a Phanerozoic steady state.

Claim 66 · checked 24 September 2026 · AI-assisted audit

What was read

A Neoproterozoic Snowball EarthHoffman, Kaufman, Halverson and Schrag, Science · Science 281 (5381), abstract as served by CrossrefAbstract only, 24 September 2026 · Copyright; quoted brieflyNo open copy found through unpaywall.
Snowball Earth climate dynamics and Cryogenian geology-geobiologyHoffman and others, Science Advances · Science Advances 3 (11), e1600983, Europe PMC full text (PMC5677351); read the abstract, Introduction, Geochronology and paleogeography, fossil record, Waterbelt solutions, cap-carbonate and oxygen sections, Table 1 and figure captions 1 to 3Read in full, 24 September 2026 · CC BY-NC 4.0Superscripts are flattened in the text as served, so "10^2 PAL" reads "102 PAL" and "10^4 or 10^5 years" reads "104 or 105 years"; excerpts keep that text so they can be matched.
Sedimentary challenge to Snowball EarthAllen and Etienne, Nature Geoscience · Nature Geoscience 1, abstract from the article page at nature.comAbstract only, 24 September 2026 · Copyright; quoted brieflyNo open copy found through unpaywall or Semantic Scholar.
Snowfall-albedo feedbacks could have led to deglaciation of snowball Earth starting from mid-latitudesde Vrese and others, Communications Earth and Environment · Communications Earth and Environment 2, article 91, publisher PDF from nature.comRead in full, 24 September 2026 · CC BY 4.0
Sea-ice thermodynamics can determine waterbelt scenarios for Snowball EarthHörner and Voigt, Earth System Dynamics · Earth System Dynamics 15, 215 to 223, publisher PDF from esd.copernicus.orgRead in full, 24 September 2026 · CC BY 4.0