A Geoscience Digital Image Library

TitleJumble of obsidian and pumice, Obsidian Dome, just north of Mammoth Lakes, California, USA
DescriptionObsidian Dome is a 600 year old (very young!) rhyolite dome near Mammoth Lakes in eastern California. It formed by rapid cooling of a viscous lava. The inner part contains some relatively solid rhyolite, but the outer parts consist of a jumbled mass of boulders and rocks of various sizes. Many are made of pumice and/or volcanic glass. A plaque near the dome says “This mile-wide, 300 foot high rhyolite dome is one of a chain of similar domes extending from Mono Lake to the Inyo Craters. The domes in the northern two-thirds of the chain are known as the Mono Craters.” The overall composition of the material shown in this picture is the same as a rhyolite (fine grained extrusive igneous rock) and a granite (coarser grained intrusive igneous rock) but cooling was so rapid that even small mineral grains did not have time to form in many of the boulders.
Geologic provinceInyo Volcanic Field
LocationUSA ▹ California ▹ Mono. Near Mammoth Lakes. Inyo National Forest.
PhotographerDexter Perkins. 2001-05-22.
Key wordsrhyolite, obsidian, pumice, granite, dome
Tech details413 KB. Vista. Canon Eos Rebel, 55 mm lens, Fuji Sensia 100.
GeoDIL number536