Tuesday, February 21, 2006

Where I'm spending my spring break

The Eldorado Mountains of southern Nevada. I'm taking a field course in geology looking at granitic intrusions and specifically the intrusions in the mountains near Nelson and Searchlight. They intruded into existing Precambrian metamorphic and earlier Cretaceous intrusions during the Miocene between 18 and 15 million years ago, just before the whole Basin and Range began extension. The extension of Nevada breaks the crust into chunks that, like a shelf of books, tilts on their side as you allow them to separate, and in this case gives wonderful access to a vertical slice of the crust that normally is buried kilometers deep. Literally speaking, you can walk from the top of an old magma chamber all the way down to the bottom of the chamber (in the case of the Searchlight pluton, it's a 10km walk).

In the above photo, the Colorado River winds in from the left side of the photo and in the far center you can see Lake Mohave. The road to Nelson comes in from the lower right. Spirit Mountain, the largest pluton in southern Nevada covering over 500km2, appears as the distant mountain to the upper right. Laughlin is not far from there. If you look closely at the large image my digital camera has a defective pixel roughly a third of the way from the center towards the right side, and it points to about where we'll be.

On the same trip in August I have a photo of Eldorado Dry Lake Bed being decidedly not dry. The dry lake is framed just below the first shot of the Eldorado Mountains--you can see the road to Nelson in both.

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