Southwest Montana

The Red Rock River Valley in southwest Montana is a crater field of multiple, oblique, low angle impacts coming from the southwest. And into the sedimentary deposits of the valley floor. The sedimentary deposits there date to the late Pleistocene, early Holocene.


swm1 The ejecta from the oval crater at 44.642265, -112.077185 was blown over the top of, and is blanketing, one of the ancient meanders of the river.



Swm5 The ejecta at 44.644033, –112.076880 that’s covering that late Pleistocene/Early Holocene meander  provides an excellent stratigraphic horizon for dating the event.


swm2 Considering the trajectory, Glacial Lake Missoula was down range. to the north, northeast.



Swm3 This cluster of fragments hit this entire valley this way. And based on my own simple impact experiments with a high powered rifle, I can say that these oval craters are consistent with a very low angle of impact into the wet sediments of the valley floor.

And this crater field is not alone. If we look back to the southwest, and directly in line with these oval craters, we’ll come to another set of oblique impact craters with exactly the same trajectory in Northern Nevada.

Almost a century ago, using aerial photography, a geologist named Harlan Bretz noticed  evidence for the mega-floods that sculpted the Grande Coulee, and the ‘Channeled Scablands’ of eastern Washington. What he had found, were the patterns of fluid flow, like the ripples you see in the sedimentary deposits of a stream bed, but these ‘ripples’ are hundreds of feet high. He saw them as empirical evidence of a major catastrophic flood event, on a scale that the standard theorists of his day thought was inconceivable.

Harlan Bretz was the first to use Aerial photographs to detect,  and map, catastrophic mass movement of the Earth’s surface materials. The aerial views allowed him a perspective from which patterns of fluid flow, and catastrophic mass movement of terrain materials, could be perceived on a scale that had been unimaginable until he described them. And most of the academic community of his time thought he had a screw loose, or two. After all, most geologists by that time had already decided to agree without question that sudden, catastrophic, geologic changes just don’t happen anymore. And that all geomorphology on the surface of the Earth is the result of slow processes we see going on around us today, and requiring millions of years. They believed that “The present is the key to understanding the past”, and that the rocks of that area were all ‘well defined’. They were mistaken.

All of the water for  ‘The Spokane Flood’ as he called it came from a glacial lake now referred to as Lake Missoula. The huge glacial lake formed during the ice age when a lobe of the Cordilleran Ice Sheet extended far enough south that it blocked the Clark Fork River in Northern Idaho.

At its highest point Lake Missoula reached a depth of 2,000 feet. And it held about 600 cubic miles of water. Whatever happened to cause the breakup of that ice dam, it was very sudden, and catastrophic. Enough ice was knocked out of the way in a very short period of time to release a flood torrent whose volume has been calculated at 8 to 10 cubic miles per hour. Or flow a rate that amounts to 10 times the combined flows of all the rivers on the planet Earth.

Apparently, being able to see the truth is no guarantee that anyone’s going to bother to look where you’re pointing anytime soon. It wasn’t until 1965 that a report from an independent geologist’s tour concluded that Harlan Bretz was right. And finally, in 1976, at the age of 96, he was awarded the Penrose Medal of the Geological Society of America. Which is just about the most prestigious award a person can get in the field of geology. Upon receiving the award, Mr. Bretz  is said to have complained to his son that he couldn’t gloat properly, because all of his enemies were dead.

The trouble we face today, Just as Mr. Bretz did back then, is that through some 19th century process of mutual-inter-assumptive reasoning, and confabulation, instead of sound, experiment-driven, science, and for more that 150 years, the Earth sciences have been founded on that unquestioned ‘Gradualist’ assumption. But gradualism only works until something sudden happens. And if you want to understand, or predict, the nature of the planetary scarring of a geologically recent catastrophic event, especially one that’s different from anything that’s ever been studied before, that 19th century, gradualist-assumptive, reasoning just won’t get you there.   

The satellites of today have upped the ante. Harlan Bretz could see evidence of catastrophic material movement on a statewide scale. With the imagery now available through Google Earth, we can detect, and read, patterns of catastrophic mass movement of terrains on a continental scale. The event Bretz perceived was only implausible from a standard theory viewpoint because of its size. And yet, by comparison, and in the final analysis, someday it may be seen that his glacial mega flood in the Pacific Northwest was only a minor little footnote in the events of the early Holocene. And some of those events were far more terrible then a glacial flood event.

Since both oblique crater fields are inline with one another, and they both have exactly the same trajectory, and they both date to the early Holocene,  it’s a fair bet they both fell in the same impact storm. Glacial Lake Missoula was just down range from them. And I can’t help but wonder:

Was this multiple fragment impact event the trigger for the break up of the ice dam at the Clark Fork River in Northern Idaho, and the resulting mega-floods that gouged the Channeled Scablands of Eastern Washington, and the Grande Coulee?

Published on November 3, 2010 at 5:44 am  Comments (2)  

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2 CommentsLeave a comment

  1. Denis,
    Great site… I sent you an email. Get back to me when you can. The animation is outstanding stuff by the way. I really enjoy the elliptical scars you found as evidence of impact.

  2. Thanks Dave,

    In the early ’70s, in central Montana, on a clear, dark night, and under a starry sky you that makes you understand why they call it ‘big sky’ country, I was privileged one time in my life to have seen a large fireball streak over, and to break up as it passed almost directly overhead. It was a big one. And It was low enough, and close enough, to hear multiple sonic booms from the fragments. And to see that some of the fragments must have gone into ‘dark flight’, and impacted somewhere over the horizon.

    Perhaps my perspective was skewed by that event. But when I imagine an impact event, I have the fragments of that fireball, and it’s low trajectory in mind as my model. I could see that, by the time it got down low in the atmosphere, it wasn’t a single, solid, object anymore. And that if any fragments made it to the ground, they weren’t flying alone. They didn’t come straight in. And I could also see that any surviving fragments would have been slowed to barely supersonic, ‘dark flight’ speeds in the atmosphere, by the low trajectory.

    You don’t need NASA’s Hypervelocity Vertical Gun Range to simulate the cratering, and ejecta patterns, of oblique impacts by small objects at such low speeds. An ordinary, high powered, rifle will do nicely for supersonic shots. And for scarring from the subsonic stuff, an air-powered pellet rifle will do.

    Shots fired at a low angle into thin, wet, clay do a nice job of simulating low velocity, oblique impacts into wet sedimentary deposits.

    You get scale models of the oval craters in southwest Montana every time.

    The oblique craters with matching trajectory in Nevada had a shallow lake as the target surface. So I did a few shots at exactly the same angle. But with the target under a layer of water. I was able to duplicate the ejecta patterns there as well.

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