A Creation Ministries International article makes the following claim about the multiple-local-flood explanation for the deposits at the Morrison Formation:

The idea of many local floods might at first seem a possibility. However, a notable feature of the water-worked sandstone in which the dinosaur bones are entombed complicates the picture for uniformitarians—these rocks contain abundant grains of a rock called ‘tuff’. Tuff forms from the solidification of hot ash ejected from volcanoes. This, and layers of volcanic ash elsewhere in the formation indicate that an explosive volcanic eruption occurred at much the same time as all the dinosaur remains were buried by flooding. No volcano is known in the vicinity of the deposit, and geologists have placed the nearest source for the tuff to vents in southern California or Nevada. Ash clouds depositing over such considerable distances point to an extremely catastrophic volcanic event.

The coincidence of floods and eruptions happening together on multiple occasions, over vast spans of time, stretches the credibility of the uniformitarian ‘just so’ story.

Has tuff been found amongst the deposits at the Dinosaur National Monument? Is this incongruous with the scientific consensus that the fossils were produced at various times hundreds of millions of years ago, rather than all at once in a worldwide flood event?

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    @hdhondt Reminds me of the Gish gallop being used outside of a debate structure.
    – JMac
    Commented Aug 15, 2018 at 11:08
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    I completely miss the logical link between ash in the fossils and the (im)possibility of many local floods happening. Sounds like non sequitur to me. Commented Aug 15, 2018 at 13:46
  • @DmitryGrigoryev: Not to affirm or contradict it... the claim is that while the consensus believes the Morrison Formation to have been formed in uniformitarian fashion through many local floods over the course of 10 million years, the presence of tuff throughout would indicate volcanic activity at each flooding event, so then the absence of nearby volcanoes calls into question the likelihood that the deposition really did take 10 million years. Commented Aug 16, 2018 at 14:27

1 Answer 1


Has tuff found amongst the deposits at the Dinosaur National Monument?

Yes. The most famous section of the rocks in Morrison Formation in Dinosaur National Monument, the Brushy Basin Member, is chock full of volcanic ash beds that have long since been converted to rock (1, 2, 3). It's also chock full of dinosaur fossils, which is what makes it so famous.

Is this incompatible with the theory that fossils were produced hundreds of millions of years ago?

Not just no, but emphatically no. In fact, exactly the opposite applies. Those many volcanic ash beds are the key to precisely dating the various parts of the Bushy Basin Member (1, 3, 4) to 148 million years old at the top of the member to 150 million years old at the bottom (4). At that time, what would become the Great Basin (i.e., just west of where Dinosaur National Monument is now) was colliding with the subducting Farallon Plate, forming a chain of volcanoes to the west (3) that occasionally dropped ash (and sometimes a lot of ash) on the area where Dinosaur National Monument is now.

The referenced Creation Ministries article makes a straw man parody of uniformitarianism to which no geologist or biologist ascribes. There have been times in the Earth's past where catastrophes have happened (e.g., the Chicxulub impact, the Deccan traps, the Siberian traps). Perfect uniformitarianism is a nonsense concept. The basic concept of uniformitarianism is not a nonsense concept. It remains a cornerstone of geology, biology, astronomy, and cosmology.

The globe looked just a bit different at the time the Brushy Basin Member formed than it does today.

The Earth, 150 million years ago


  1. Christiansen, Eric H., Bart J. Kowallis, Michael J. Dorais, Garret L. Hart, Chloe N. Mills, Megan Pickard, and Eric Parks. "The record of volcanism in the Brushy Basin Member of the Morrison Formation: Implications for the Late Jurassic of western North America." Geol Soc Am Spec Pap 513 (2015): 399-439.
  2. Bell, Thomas E. "Deposition and diagenesis of the Brushy Basin Member and upper part of the Westwater Canyon Member of the Morrison Formation, San Juan Basin, New Mexico." in SG 22: A Basin Analysis Case Study: Morrison Formation, Grants Uranium Region, New Mexico (1986): 77-91.
  3. DeCelles, Peter G. "Late Jurassic to Eocene evolution of the Cordilleran thrust belt and foreland basin system, western USA." American Journal of Science 304, no. 2 (2004): 105-168.
  4. Kowallis, Bart J., Eric H. Christiansen, Alan L. Deino, Fred Peterson, Christine E. Turner, Michael J. Kunk, and John D. Obradovich. "The age of the Morrison Formation." Modern Geology 22, no. 1-4 (1998): 235-260.
  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Sklivvz
    Commented Aug 15, 2018 at 19:37
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    I don't think that the theory under scrutiny by the article in question is general uniformitarianism, but rather the consequence of our scientific consensus that the ash and flood events all happened at different times, rather than all at once. Naming volcanic ash as the raw material for geologic dating does not apply the opposite conclusion to the evidence, although it does point toward the consensus. Commented Aug 15, 2018 at 22:44
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    @elliotsvensson - Make no doubt: The theory under scrutiny by the referenced article is almost all of science, except perhaps chemistry and the medical sciences (so long as they steer clear of evolution). Physics, astronomy, anthropology, cosmology, geology ..., and evolutionary biology (the worst offender saved for last) represent threats to a literal belief in just about any religious text. Commented Aug 16, 2018 at 3:05

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