Thursday, April 11, 2013

Crevasse Splays

I can think of few events in my life that can compare to digging up dinosaurs with Alan Titus. Not that there haven't been fantastic moments in my life, but digging up dinosaurs with a busy paleontologist is just kind of unique experience that not a lot of things compare to. That just goes to show how incredible geology really is.

While working with Alan, digging up what we think to be a Hadrosaur, in the Grand Staircase National Monument, I was told about an interesting event that happens along rivers called a crevasse splay. Some of the dinosaurs were found in crevasse splay deposits. My interest was peaked and so I will attempt to paint a picture for you.

Imagine that it is the rainy season of the year. The river's banks are filling and soon the water will overcome the levees. It isn't anything new to the area seeing as this is a well established meandering river. As you are overlooking the river, you see a weak point in the levee begin to give to the weight of water against it. All of the sudden the river breaks through at that point. It starts out small but rapidly grows into a side channel. The swift moving water from the river cuts a ravine in the soft levee sediment. As you look past that point where the levee broke, you see a Hadrosaur grazing in the flood plain. You call out to it to move out of danger but it is too late. The water overtakes the dinosaur and it disappears from view. Soon you can see the sediment carried from the river, through the crevasse, and out into the flood plain settling into a fan shape. You, however, don't see the unfortunate Hadrosaur.

This is an aerial  view of a crevasse splay. One much like an unsuspecting Hadrosaur could get caught up in. Turns out that crevasse splays are fantastic places to find well preserved dinosaurs. However, sometimes the river's cut bank will erode far enough into the flood plain to scour out buried dinosaurs and other fossils. Pretty cool stuff, right?

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