SF-0020Nature Is Terrifying
A 30-metre rock made a 1.2-kilometre hole, and a mineral made impact craters recognisable
The USGS puts the impactor at about 30 metres across and 100,000 tons, arriving at 12–20 km/sec with the force of over two million tons of TNT. The hole it left is 1.2 km wide and 180 m deep.
Meteor Crater from the air. The buildings on the far rim and the road crossing the plain are the only things in the frame that give the bowl its size — 1.2 kilometres across.
Aerial view of Meteor Crater, color, Coconino County, Arizona.
- Image
- David John Roddy
- Taken
- 1975
- Location
- Coconino County, Arizona
- Archive ref.
- USGS media library — Astrogeology Science Center, rdj00001_cp
- Licence
- Public domain per the USGS media library's item-level Sources/Usage statement (licence record)
- The image itself
- Authentic, unaltered
"Aerial view of Meteor Crater, color, Coconino County, Arizona." David John Roddy, US Geological Survey media library, c. 1975. Public domain. Cropped.
Verdict
"It's obviously a meteor crater — there's the hole, and there are the meteorite fragments."
The core of the claim holds up, but a specific detail as it circulates is wrong or overstated.
The conclusion is correct and the reasoning attributed to it is not the reasoning that settled it.
TRUE: it is an impact crater, and the USGS states this without qualification — "Meteor Crater is a 180 m deep, 1.2 km diameter bowl-shaped impact crater in Northern Arizona", formed "approximately 50,000 years ago by the impact of a 100,000-ton iron-nickel meteorite, ~30 m in diameter, which struck at an approximate speed of 12-20 km/sec."
NOT THE WHOLE STORY: that the crater and the fragments are what demonstrated it. The USGS credits "the works of Daniel Barringer and Eugene Shoemaker" with having "demonstrated conclusive evidence for the impact origin of the crater", and it is specific about what Shoemaker's contribution consisted of: research between 1957 and 1960 on the structure and mechanics of meteorite impact, "including the discovery of coesite (a high pressure form of silica created during impacts) with E.C.T. Chao", which "provided the definitive work on basic impact cratering."
The 1960 paper is titled, flatly, "First natural occurrence of coesite from Meteor Crater, Arizona". A mineral that had been made in a laboratory and never found in the ground turned up in the sandstone here — and that is what made shock metamorphism a test you can carry to any crater anywhere.
Mostly True requires 1 primary or authoritative source. This file cites 3.
In short
Meteor Crater in northern Arizona is a bowl 1.2 kilometres across and 180 metres deep, made roughly 50,000 years ago by an iron-nickel meteorite the USGS describes as around 30 metres in diameter. The crater is forty times wider than the object that made it. And the thing that turned "probably an impact" into a method for recognising impacts anywhere was not the crater or the iron fragments around it — it was coesite, a high-pressure form of silica whose first natural occurrence on Earth was identified here in 1960.
The ratio
Meteor Crater is a bowl 1.2 kilometres across and 180 metres deep. The object that made it, the USGS says, was an iron-nickel meteorite about 30 metres in diameter, weighing on the order of 100,000 tons, arriving at somewhere between 12 and 20 kilometres per second.
Forty times wider than the thing that hit it. The energy is given as more than two million tons of TNT — around 150 times the Hiroshima bomb — delivered by an object you could park across a suburban street.
That is most of why the place is worth looking at. It is a legible, human-scale demonstration that the damage an impact does has very little to do with how big the rock is and almost everything to do with how fast it is going.
The part that isn’t obvious
Stand on the rim and the explanation seems to supply itself: a hole, and iron fragments scattered across the plain around it, collected since the 1890s. What else would it be?
But “iron landed here” and “this crater was made by an impact” are different statements, and the second one is the useful one, because it is the one you can take somewhere else. A method that only works where you happen to find meteorite fragments lying about is not a method.
The USGS credits the demonstration to sustained work rather than to the view — “the works of Daniel Barringer and Eugene Shoemaker have demonstrated conclusive evidence for the impact origin” — and is specific about Shoemaker’s part:
In the period 1957-1960, he did his classic research on the structure and mechanics of meteorite impact. This work—including the discovery of coesite (a high pressure form of silica created during impacts) with E.C.T. Chao—provided the definitive work on basic impact cratering.
A mineral that had only ever existed in a laboratory
Coesite is a high-pressure form of silica. It had been synthesised under pressures that do not occur at the Earth’s surface, and it had never been found in nature.
Then it was found in the sandstone at Meteor Crater. The paper, published in 1960 by Chao, Shoemaker and Madsen, is titled — with no ornament at all — First natural occurrence of coesite from Meteor Crater, Arizona.
That is the moment the crater stops being one interesting hole in Arizona. Rock that has been shocked hard enough to make coesite is rock that has been hit, and nothing else. The test travels. Within a few years Shoemaker was at the crater training Apollo astronauts to read the Moon.
What this file does not claim
That the meteorite fragments were irrelevant — the USGS names Barringer alongside Shoemaker, and the iron is real.
That Meteor Crater was once thought volcanic. That story is widely told and no USGS page consulted here mentions it, so this file leaves it alone rather than repeating a history of scientific opinion on the strength of it sounding right.
That the 1960 paper says more than its title. It was not read — the publication page returned a 403 — and it is cited exactly as the agency cites it.
And nothing about what became of the meteorite. There is an ejecta blanket with fragments, melt and metallic spherules in it; whether anything substantial survives below the floor is a question this file did not go near.
The evidence
The USGS states the origin without hedging: "Meteor Crater is a 180 m deep, 1.2 km diameter bowl-shaped impact crater in Northern Arizona."
Cited sources:S1
The impactor was small relative to its hole. The crater "formed approximately 50,000 years ago by the impact of a 100,000-ton iron-nickel meteorite, ~30 m in diameter, which struck at an approximate speed of 12-20 km/sec." A 1.2 km crater from a ~30 m object is a ratio of about forty to one.
The energy is given in terms that make the ratio legible: an explosion "with force equivalent to over 2 million tons of TNT", which the USGS elsewhere renders as about 150 times the force of the bomb detonated over Hiroshima.
Cited sources:S2
The USGS attributes the demonstration to sustained study rather than to the site's appearance: "Geologic and petrologic studies of Meteor Crater, especially the works of Daniel Barringer and Eugene Shoemaker, have demonstrated conclusive evidence for the impact origin of the crater."
Cited sources:S1
What Shoemaker's part consisted of is stated specifically. "In the period 1957-1960, he did his classic research on the structure and mechanics of meteorite impact. This work—including the discovery of coesite (a high pressure form of silica created during impacts) with E.C.T. Chao—provided the definitive work on basic impact cratering."
Cited sources:S3
The coesite result is recorded by the USGS under a title that states its own significance: "First natural occurrence of coesite from Meteor Crater, Arizona", published in 1960 by Chao, Shoemaker and Madsen. A mineral previously known only as a laboratory product was identified in the ground.
Cited sources:S1
The site became a training ground for reading other worlds: "During the 1960's, Eugene Shoemaker trained NASA astronauts at the crater to prepare for the Apollo missions to the Moon."
Cited sources:S1
Shock metamorphism remains an active research subject at the site rather than a settled historical footnote. The USGS lists its Meteor Crater sample collection as supporting work on "impact melting of sedimentary targets, ejecta distribution and deposition processes, and mineral shock metamorphism."
Cited sources:S1
Evidence that cuts the other way
Findings that complicate or argue against the verdict above. They are listed because leaving them out would make the file look stronger than it is.
The fragments were not nothing, and this file should not imply they were. Iron from the Canyon Diablo meteorite has been recovered around the crater since the nineteenth century, and the USGS names Daniel Barringer alongside Shoemaker among those whose work demonstrated the impact origin. The correction is about what made impact craters identifiable in general, not a claim that the fragments were irrelevant here.
Cited sources:S1
This file does not establish what the competing explanation was, or that one was ever widely held. It is often said that the crater was long attributed to volcanism, and no USGS page read here says so — none mentions a volcanic or steam-explosion hypothesis at all. The claim being corrected is therefore the modern casual one about what the evidence is, not a historical claim about what scientists once believed, which would need sources this file does not have.
The 1960 coesite paper itself was not read. Its existence, title, authors and year are recorded by the USGS pages cited here; the publication page returned HTTP 403. Nothing in this file depends on its contents beyond what those pages state about it.
Cited sources:S1
What we still don’t know
- What was believed before, and by whom. This file establishes what settled the science; it does not establish what preceded it. No USGS page read here mentions a volcanic or steam-explosion hypothesis for Meteor Crater, so no history of a displaced explanation is asserted, however familiar that story is.
- The contents of the 1960 coesite paper. Its title, authors and year are recorded by the USGS pages cited; the publication page itself returned HTTP 403 and was not read. What coesite requires in pressure terms, and how the identification was made, are therefore not stated here.
- The impactor's size and speed are given by the USGS as approximations — "~30 m", "12-20 km/sec" — and the mass as a round 100,000 tons. The forty-to-one ratio between crater and object in this file is arithmetic on those approximations, not a measured figure, and is described that way.
- What happened to the meteorite. The USGS describes an ejecta blanket containing meteorite fragments, impact melt and metallic spherules, and this file does not go further. Whether a substantial mass survives beneath the crater floor is a question with a long history that no source read here addresses.
- The crater's age is given as "approximately 50,000 years" with no method or error stated, and no dating study was consulted.
Sources
Every source below was read in full before it was cited. Archive snapshots are recorded at research time, because a file whose sources have evaporated is indistinguishable from one that never had any.
S1Tier 1Read in full
Meteor Crater Sample Collection
US Geological Survey, Astrogeology Science Center
The agency's own page for its Meteor Crater collection, and the spine of this file. Establishes the crater as "a 180 m deep, 1.2 km diameter bowl-shaped impact crater"; the age of approximately 50,000 years; the impactor as "a 100,000-ton iron-nickel meteorite, ~30 m in diameter" at "12-20 km/sec"; the Canyon Diablo naming; the attribution of conclusive evidence to "the works of Daniel Barringer and Eugene Shoemaker"; the 1960 Chao, Shoemaker and Madsen publication "First natural occurrence of coesite from Meteor Crater, Arizona"; Shoemaker's Apollo astronaut training at the site in the 1960s; and shock metamorphism as a continuing research focus.
S2Tier 1Read in full
Aerial view of Meteor Crater, color, Coconino County, Arizona — USGS media library item
David John Roddy · US Geological Survey · 1975
The image's rights record and caption. Establishes the item-level "Sources/Usage: Public Domain" statement and the photographer credit, and — read a second time for literal on-page text — establishes by its absence that no affiliation is printed, which is what narrowed the public-domain basis. Its description also carries the energy figure, "force equivalent to over 2 million tons of TNT", and the account of the ejecta blanket of pulverised material, meteorite fragments, impact melt and metallic spherules.
S3Tier 1Read in full
Gene Shoemaker — Founder of Astrogeology
US Geological Survey, Astrogeology Science Center
The agency's biographical account, cited for one specific thing: what Shoemaker's 1957–1960 research consisted of and what it achieved — "including the discovery of coesite (a high pressure form of silica created during impacts) with E.C.T. Chao" and the judgement that this "provided the definitive work on basic impact cratering." It also places Meteor Crater as "the one impact structure on the Colorado Plateau" among the volcanic features Shoemaker worked on, and says nothing about any earlier volcanic interpretation of the crater itself.
Checked for circularity: S1 and S2; S2 and S3 were confirmed not to derive from one another. Two sources that trace back to the same origin are one source, and counting them twice is the most common way a false claim looks well-evidenced.
How we checked this
What we went looking for, and what we found
Four checks, two of which changed the file, and one of which removed its original premise.
First, and most consequential: the file was commissioned around "the evidence that displaced the volcanic explanation". That premise was abandoned because it could not be sourced. Not one USGS page read here — the sample collection page, the Shoemaker biography, the image item — mentions a volcanic or steam-explosion hypothesis for Meteor Crater at all. The story is familiar and may well be true, and this file will not assert a history of scientific opinion on the strength of it being familiar. The claim was re-pointed at what the sources do establish: what settled the science, rather than what it replaced. Recorded as contradicting evidence and as an uncertainty.
Second, against overcorrecting in the other direction. Having found that coesite is what the USGS credits, it would be easy to write the fragments out of the story. The USGS names Barringer alongside Shoemaker, and iron has been coming off that plain since the 1890s. The correction is about what made impact craters recognisable in general, and the file says so.
Third, on the 1960 paper. Its publication page returns 403 and it was not read. It is cited only as the USGS pages cite it — title, authors, year — and nothing is claimed about its contents.
Fourth, on the image metadata, where a text scan would have produced a false alarm rather than a false negative. The embedded ICC profile carries "Copyright (C) SEIKO EPSON CORPORATION 2007. All rights reserved." That is a scanner profile, not a claim on the photograph, and it is recorded in the rights note rather than quietly deleted, because the next person to run a text search over this file will find that string and needs to already know what it is.
- We searched for evidence against our own conclusion
- We traced where the claim started
- The claim is stated in its strongest form, not a weak version
- The photograph was verified independently of the story
- We checked whether this was settled after the popular version froze
- Image rights were traced to a stated licence
- We checked what we were leaving out
- The verdict sat before publication, and was re-read cold
- Confidence in the verdict
- high
- Verdict assigned
- Most recent authoritative source
- Researched by
- The Strange File
COOLING-OFF PASSED 2026-08-01. The verdict was assigned 2026-07-31 and the wait has elapsed. The fresh-eyes pass was made by a session that neither researched nor wrote this file, re-reading the dossier, the evidence, the sources, the verdict reasoning, the rights record and the Quick File cold. The headline read "a mineral is what proved it", crediting coesite alone where the USGS wording quoted in this file attributes the demonstration to "the works of Daniel Barringer and Eugene Shoemaker". This file's own contradicting evidence exists to stop the fragments being written out, and the headline wrote them out anyway. Corrected to what USGS supports, and the Quick File correction re-pointed the same way.
That pass is cooling-off and nothing else. Cooling-off, independent review and the owner's approval remain three separate controls and none may stand in for another. No independent review has occurred; this file carries no sensitivity flag, so none is required. The owner has not approved publication, and READY is not permission to publish.
No sensitivity flag, and the check was made rather than skipped. The event is roughly 50,000 years old, no casualties are recorded or implied, and no living person is named. The site is privately owned and commercially operated; this file makes no claim about its ownership, management or admission, and uses no imagery from it.
The named individuals — Barringer, Shoemaker, Chao, Madsen, and the photographer Roddy — are named for published scientific work and a credited photograph, which is the whole of what is said about any of them.
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