Glass Mountain

Glass Mountain is a volcanic summit in Mono County that rises to about 11,100 feet, forming the northeast boundary of the Long Valley Caldera. Its surface consists mainly of rhyolite, a volcanic rock that gives the mountain its distinctive glassy appearance.

The mountain formed through intense volcanic activity between roughly two and one million years ago, when magma pushed to the surface and cooled rapidly. This geological history created the obsidian and glass deposits that now characterize the landscape.

The mountain holds significance for the region's indigenous peoples, whose ancestors valued its obsidian deposits for practical and trade purposes. Visitors can observe the scattered glass fragments on the slopes, connecting them to this heritage.

The route to the summit involves driving on unpaved forest roads that can become difficult in bad weather. Sturdy footwear is essential since the surface is covered with sharp glass fragments and exposed rock.

The gleaming glass fragments covering the slope are actually obsidian, a naturally occurring volcanic glass formed when lava cooled rapidly. This natural shine makes the mountain recognizable from a distance and transforms it into something resembling a giant piece of volcanic jewelry.

Location: California

Made from material: rhyolite

GPS coordinates: 37.77493,-118.70846

Latest update: December 10, 2025 16:00