California Volcano Observatory

The two-color EDM network located near Mammoth Lakes, California is within the Long Valley caldera and has had recent, volcanic unrest. The Long Valley Caldera is located east of the Sierra Nevada mountains.

Map of Long Valley Net

This map shows the locations of baselines that are measured in the Long Valley Caldera, near Mammoth Lakes, California, using a two-color laser distance measuring instrument (geodimeter). The two-color geodimeter measures distances to a precision of 0.5 to 1.0 mm for ranges between 3 and 8 km. The locations of these baselines are shown in relation to sources of inflation that have been modeled using both these data and leveling data.

Plots of the changes in length of 8 frequently measured baselines are available through the links listed below. These baselines, which use the central station at CASA as a common end point, have been measured approximately 3 times each week since early 1984. The general trend of the data is: 1) a general decrease in the rate of extension from 1983 through most of 1989; 2) an abrupt increase in the rate of extension on several baselines to 5 cm/yr from late 1989 through early 1990; and 3) a decrease to 2 to 3 cm/yr extension rate that has persisted since mid-1990.

The Data

Download raw data.

NEW! Combination EDM and GPS line-length changes from 1984

The twocolor EDM has been replaced by continuous GPS. Many of the GPS sites are co-located with the EDM sites. Consequently, the length changes that had been monitored with the EDM are now being monitored with GPS. Below are plots of the continuation of the EDM time series using both the older EDM data and the newer GPS data.

For more details contact: John Langbein