Geologic Trip, Mono Lakes Area
The Mono Craters were formed by volcanic activity that started about 40,000 years ago and has continued up to the present time. There are about 30 volcanic centers along the Mono Craters. Most eruptions followed a general sequence of events. The eruption would begin when stiff rhyolite magma forced its way to the surface along a crack in the earth’s crust. Ash and coarse pumice were then thrown from the vent. After this, the vent would clear its throat with a large explosion that created a crater with a rim of pumice, rock debris, and fragments of bedrock. Stiff rhyolite magma would then ooze from the vent like toothpaste, leaving a small rhyolite plug in the center of the crater.