During fall break, October 14 through October 22 the Geology Department will sponsor a field trip to the Mammoth Lakes region of California. This trip is open to all interested students, although priority will be given to students taking a course in the Geology Department. What is involved?

The town of Mammoth Lakes, California. is at an elevation of 8000' at the west end of the Long Valley caldera, an elliptical valley which has been active volcanically for over 3 million years. Immediately to the west and south of the town is the eastern scarp of the Sierra Nevada mountains, which have been experiencing rapid uplift for the past ~5 million years. The town is also known for its ski slopes, located on Mammoth Mountain a volcano (looks like one, too) situated just SW of the town, and rising to over 11,000'.

Among other geological features of this area, about 760,000 years ago a cataclysmic volcanic eruption in the area blew out 150 cubic miles of magma (molten rock) from a depth of about 4 miles beneath the Earth's surface. This region continues to experience minor, but conclusive, signs of magma (molten rock) beneath the surface. A chain of young volcanic structures, the Mono-Inyo chain of craters, extends northward from the town and crosses the north rim of the caldera. The youngest of these, are steam-driven explosion craters just 600 years old. The south flank of Mammoth Mountain has been the site of well- publicized emissions of subsurface carbon dioxide.

This geologically active area is closely monitored for earthquakes (see a daily record of quakes starting on Oct 10) and other signs of impending igneous and tectonic activity. At depths of 2-10 km, swarms of small earthquakes occur in patterns characteristic of active calderas around the world. The region just to the east of town is a "resurgent dome" and has experienced over 1 meter of uplift since monitoring began in the 1980's. It continues to show additional uplift each year on US Geological Survey instruments.

Earthquakes from 1978 to 1994.

Check out the USGS Information from the Long Valley Observatory as well as the fact sheet from the US Geological Survey: Living With a Restless Caldera—Long Valley, California. Also you can learn about the volcanic features of the area. These include, among other things, Devil's Postpile National Monument.

Mono Lake is an oasis in the dry Great Basin just north of Mammoth. One of its interesting features is the deposition of calcium carbonate forming fantastic tufa towers.

If you would like to see more of this area access the virtual guidebook of Mono Lake.

We will also get a chance to drive over to Yosemite and see masses of granite sculpted by glaciers. There is also a virtual guidebook of this area.

 Questions?