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Thread: Ice Age Floods

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    libertine librarian sandwitch's Avatar
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    Ice Age Floods

    This shit is off the hook.

    I went to a lecture on the Ice Age floods at Dry Falls State Park. There's a massive hole in the ground that was carved away as ice dams melted and released walls of water across eastern Washington. Here's what I understand of its history: The area is composed of basalt layers from a long history of lava flows and re-directions of the Columbia River. Over time, the basalt stretched, creating cracks that were further compromised by 350' of rapidly flowing water. There's no archaeological evidence of human inhabitation, but if anyone was there it would have been a bad time. Stones pulled from the ground were carried as far as the Pacific Ocean.



    My geologist grandfather describes the geology of Washington state as "notoriously complicated." It's largely formed by a patchwork of volcanic islands and bits of ocean floor. It's relatively young and unfortunately under-taught. Burke Museum: Northwest Origins has one of the better narratives available.

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    Eastern Washington, so that's past the rainshadow, right? It's funny, I'm not inclined to think of Washington as having deserts, just evergreen forests. If I didn't know better, I'd say that footage was from Arizona.

    What's interesting to me is that this must be very geologically recent. This must have been a cataclysmic reshaping. The Ice Age really wasn't that long ago, but it seems to have changed quite a lot.


    I would love to know more about the geology of the Delaware Valley. I know a little bit about the geology of the Hudson Valley (and no, it was not Ithaca that was my primary reference point). The catskills are really just an eroded plateau by glacial action, and not formed by tectonic activity at all. During the Devonian period (I believe), it was all underwater, part of a large shallow sea, and you can find fossils of ancient seashells (brachipods) alongside highways. I went to a field trip to a quarry that they used for, among other things, the base of the statue of liberty. It wasn't like you would have expected for a quarry... it consisted of odd diagonal shafts going deep, deep down underground. We got to get some fossils from the area around the quarry. I have a jar full of them.

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    libertine librarian sandwitch's Avatar
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    If you look at satellite images of the northwest you'll see that the area is very environmentally diverse. I grew up in the foothills of the Cascades, where the hills would dry up mid-June, but the nearby mountain trails could still be snowed over. The south-east corner of the state is mostly cattle and wheatfields.

    The ice age floods would have been in the last 2 million years. The landmass as a whole is relatively young- I believe the Cascades are the newest mountain range in North America. There's an uncomfortable number of volcanoes that could erupt at any given time. I hear there's still gold in them hills.

    It's a little embarressing how little I know about the geology of the rest of the continent, but I'm glad that my parents forced me to go on roadtrips and climb on rocks as a kid.

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