“To learn the secret of history, you must first pay attention to the natural history of granite and understand geologic time.”
~ Lisa Veyssiere from her essay “The Orbit of Known Objects” (published in “Tahoe Blues: Short Lit on Life at the Lake”)
For many people, large gray boulders sprinkled with salt and pepper sparkles, yellow or green or orange lichen, and white striated lines represent the Sierra. Donner Summit, Desolation Wilderness, Mt. Tallac — anywhere we look up, granite strikes our alpine imagination. Those of us who live in the Sierra boast to the world that our hiking trails offer granite stepping stones; our tennis shoes and hiking boots easily grip the solid rocks like suction cups to a smooth surface. Really, is there anything more fun and playful than leaping from one granite boulder to the next?
But what exactly is granite? What is it made of? And where did it come from?
To understand how granite was originally formed, Frank DeCourten, professor of earth science at Sierra College and author of “The Broken Land: Adventures in Great Basin Geology,” explains the complex formation of granite by likening it to a bag of one of America’s favorite confections. In his essay, “Granite: The Stone Heart of the Sierra,” DeCourten writes, “So complex are the Sierra Nevada batholiths (large underground masses of igneous rock, which were formed through the cooling and solidification of magma) that their structure has been compared to a bag of marshmallows: Many individual granite masses are huddled closely together to constitute a larger mass. Each granite body represents a distinct bubble (a “marshmallow”) of magma that migrated upward into the earth’s crust, primarily between 80 and 110 million years ago. For some 30 million years, bodies of magma flooded upward into crust, cooling and solidifying adjacent to older batholiths that were already in place.” The different colors we see in granite depend on that mixing of older and newer batholiths, each one varying in color and texture depending on the proportion of minerals. For instance, quartz and feldspar are light colored, pinkish to white, while hornblende and biotite (a mica) are dark colored, brown to black to dark green. The name “granite” stems from the rock having a grained or granular coarse texture.
When I lived in southern Oregon and hiked in tangled, bushy manzanita and madrone on unsteady volcanic plateaus, I missed the Sierra. I missed granite. As it’s said, “You don’t know what you’ve got till it’s gone.” Without granite under my feet and vistas of layered silver rock and car-sized boulders, the mountains just didn’t feel right. Ever since I lived in that thick, brushy country, I have never taken granite for granted. Ever.
~ Do you have a question about our region’s natural world? Email mountainlife@moonshineink.com. Comment on this column below.
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