Obsidian Dome

Obsidian Dome is the result of a volcanic eruption in the year 1350 CE (“Current Era”)

Obsidian Dome is the result of a volcanic eruption in the year 1350 CE (“Current Era”)

Obsidian Dome is a geology nerd’s dream. Nerd fact number one: The eruption date for the area around Obsidian Dome is one of the best estimated eruption dates in the prehistoric period on the planet. 

By using tree ring dating, scientists found that the eruptions that created Obsidian Dome, as well as Glass Creek and Deadman Creek, occurred in late summer, 1350 CE (“Current Era”). 

Obsidian Dome is about a three mile drive from Highway 395 (turn onto Obsidian Dome Road between the southern exit of the June Lake junction and Crestview) on a dirt road. Meandering paths lead up to various vista points where visitors can view the domes (you can climb to a height of almost 400 feet on obsidian alone). 

“To understand how obsidian is extruded from the earth, imagine holding a tube of toothpaste upright and slowly squeezing the tube,” reads a U.S. Forest Service brochure on the Dome. “The thick viscous material forms a column which will fall quickly for lack of solid support. Now go a step further and imagine that instead of toothpaste, your tube is full of melted glass (like obsidian). When the column of glass comes in contact with air, the outside cools and stops moving. The inside of the column continues to move because it’s under pressure. The outside skin becomes brittle and falls away.” 

The resulting rock is so hard, and so easily chipped into a razor-sharp edge, that the Mono Lake Paiute of the Eastern Sierra prized it above all other stone for arrowheads (nerd fact number two). In fact, the Native Americans of the Long Valley Caldera were able to trade this naturally-occurring stone far and wide—an archeological recovery at coastal Chumash sites in California indicate trade with the residents of the Eastern Sierra, according to a 2008 paper by C. Michael Hogan. 

In the winter, groomed trails lead out to the dome, and the black obsidian beneath a fresh snowfall is truly a sight to see. Cross-country skiing to Obsidian Dome is very enjoyable, with the trail a relatively mellow meander up to some incredible vistas. 

If you have the opportunity, pick up a copy of “Roadside Geology of the Owens Valley” in order to get a better understanding of what makes this place so special. 

Sarah Rea is a freelance dirtbag-turned-journalist who has been living in the Sierra on and off for twenty years, with eight spent in Yosemite National Park and five in Mammoth Lakes. She likes dogs, rocks, good food and jumping into cold water.