> Come to find out it could be the remnant of the Long Valley Caldera blast or the numerous blasts that have occured near and around Mammoth. I am fascinated with fault lines, plate tectonics, scarps, earthquakes, and volcanos and how they sculpted the Sierra Nevada.
Well... not exactly. That obsidian was put there by humans. ...Native Americans.
Tioga Pass or Mono pass just to the south was a main trading trail for the American Indians. They carried obsidian across the Sierra to trade with others. It was the primary source of arrowheads. It can be found down around Mammoth, Glass Mountain, I believe.
Hiking over Donohue Pass out of Yosemite, as you climb out of the Lyell Canyon there is a place along the trail where there is obsidian lying all over the place ...on top of granite. It must have been an Indian camp where they made arrowheads.
The big effect of the Long Valley Caldera is the expansive volcanic tuff deposit north of Bishop. Every time you drive north on 395, you can see the pinkish-tan cliffs along the Owens River before you climb to the Sherwin summit. That entire smooth but rocky slope up that grade is made of cubic miles of volcanic tuff that exploded out of the caldera in one cataclysmic eruption. (former geology major here).
