Plate Tectonics and Volcanism in Western California

Fact Sheet 2025-3013
By:

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Introduction 

Western California is home to a variety of volcanic rocks. The locations, ages, and chemical compositions of these volcanic rocks help tell part of the fascinating story of California’s plate tectonic evolution over the past 40 million years. These volcanic rocks are a product of multiple tectonic processes, including subduction of divergent and transform plate boundaries beneath continental North America, opening of a slab window, creation and migration of a tectonic triple junction, and the birth and growth of the San Andreas Fault. This fact sheet explains these tectonic processes and discusses their role in shaping the volcanic history of western California over the past 40 million years. By studying the volcanic rock record in western California, geologists are able to piece together how regional volcanism and plate tectonics are linked in space and time. Recognizing this linkage helps scientists to understand possible future volcanism in the region, potential hazards associated with this volcanism, and the impacts these hazards may have on population and infrastructure. The U.S. Geological Survey California Volcano Observatory (CalVO) closely monitors the parts of western California with the greatest potential for volcanism.

Suggested Citation

Burgess, S., 2025, Plate tectonics and volcanism in western California: U.S. Geological Survey Fact Sheet 2025–3013, 4 p., https://doi.org/10.3133/fs20253013.

ISSN: 2327-6932 (online)

ISSN: 2327-6916 (print)

Study Area

Publication type Report
Publication Subtype USGS Numbered Series
Title Plate tectonics and volcanism in western California
Series title Fact Sheet
Series number 2025-3013
DOI 10.3133/fs20253013
Publication Date November 18, 2025
Year Published 2025
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Volcano Science Center
Description 4 p.
Country United States
State California
Other Geospatial western California
Online Only (Y/N) N
Additional publication details