Monday, March 21, 2011

The rocks of Spring Break '11

Spring break. While getting drunk in a sunny place would have been fun, I spent the week looking at rocks, sometimes in the sun and sometimes in the snow. A group of us went out west, using Mammoth Lakes, CA as a base for trips to Mono Lake, the Sierras, the Long Valley Caldera, and the mountains of the Basin and Range.

Unable to help myself, I came home with at least 20 different rocks, each one chosen for some reason, either aesthetic or scientific. So that's what this post is about: the rocks.

(1) The first one is a volcanic bomb from Panum Crater, the northernmost of the Mono Craters, a chain of volcanoes that have erupted within the last 40,000 years. Panum is young, only about 600 years old, and is full of interesting textures, colors, and formations. There is jet black obsidian, sharp enough to kill, and frothy, red pumice stones. The rock shown here, a volcanic bomb, is a piece of magma that shot out of the volcano as a liquid, and, by the time it had hit the ground, had solidified into a coherent mass. You can see that it's elongated in one direction, along the axis of it's fall from the sky. I picked this one because it looks like a small man.


(2) Petrified wood from Miocene sediments near Coaldale Junction, NV. Coaldale Junction is not an actual place, consisting of a few abandoned buildings in the middle of the big, empty Nevada desert. The rocks here are amazing, including a unit that contains beautifully preserved petrified wood from about 12 million years ago. There are knotted pieces, branches, bark, many covered with sparkling quartz crystals. I picked the two fragments shown here because one contains a knot, a clearly recognizable tree structure preserved for eternity in solid rock and the other is a dead ringer for a real piece of bark.



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