Sonoma Volcanic Area

(San Francisco Bay Region 3D image tour)

Click on a small image to open a larger 3D image.

A typical lively discussion amongst USGS scientists takes place on outcrops of volcanic tuff associated with the Sonoma Volcanic Field. This exposure is along Frans Valley School Road (near Callistoga). Geochronologic dating of samples from this outcrop area provided an age estimate of 2.78 million years.

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Last modified 11/24/2003