The need for a simplified geological guide to Mount Diablo to accompany Memoir 217 was recognized by the Northern California Geological Society, Mount Diablo Interpretive Association, and California State Parks. A folded two-sided guide, edited by Greg Bartow, is now available, that consists of an updated geologic map with roads and trails on one side, and a description of the geology on the other side. The updated geologic map, by Russell Graymer and Victoria Langenheim of the U.S. Geological Survey, also appears in Chapter 1 of GSA Memoir 217. The guide includes a map showing the epicenters of 7,200 earthquakes that have occurred in the vicinity of Mount Diablo over the last 36 years. These earthquakes illustrate the active nature of the fault systems that continue to form Mount Diablo. Stephen Smith, President of Mount Diablo Interpretive Association, said, “This geologic guide will provide a new resource for visitors to appreciate the unique nature of the park.”

Mount Diablo State Park draws more than 600,000 visitors each year to explore the park and take in the spectacular view. Mount Diablo Interpretive Association (MDIA) is a non-profit, all-volunteer organization that assists the California Department of Parks and Recreation in maintaining and interpreting Mount Diablo State Park. Through education, sponsored activities, and publications, MDIA fosters appreciation and the enlightened use of Mount Diablo State Park. Save Mount Diablo is a non-profit organization dedicated to the preservation of Mount Diablo peaks, surrounding foothills and watersheds through land acquisitions.

Copies of the geologic map can be purchased online at the MDIA Store for $7.00 (shipping included), or for $6.00 at the Visitor Centers at Mount Diablo State Park Summit and Mitchell Canyon.