One of the geological features of the Mono-Inyo volcanic crater chain near Mammoth Lakes, CA, Obsidian Dome is a lava dome composed of rhyolite, obsidian, and pumice.
The dome formed from volcanic eruptions, which occurred about 600 years ago, that oozed sticky substance to the surface. The volcanic crater chain runs north and south and is dotted by volcanic vents along the Long Valley Caldera Field.
Obsidian Dome is located near Dead Man Summit, south of June Lake Loop, which is along Highway 395. It is a mile-long mound of glass that extends about 300 feet high. Visitors can climb the mound to see the different rock compositions. Materials found here were used to make arrowheads, spearheads, and knives, which were the main trade of the Paiute Indians in the area. There is parking available at the dome. To find the dome, from Mammoth Lakes take Highway 395 to Obsidian Dome Road. The last 2.7 miles is a dirt road that ends at the parking lot.
Obsidian Dome is located 175 miles east of San Francisco and southeast of Yosemite National Park. While visiting this site, tourists might also enjoy other nearby sights: Scenic Summer Gondola, the Hayden Cabin, McGee Creek Lodge, and Consolidated Gold Mine.