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U.S. Geological Survey Scientific Investigations Report 2012–5176–A

Volcano Hazards Assessment for the Lassen Region, Northern California

By Michael A. Clynne, Joel E. Robinson, Manuel Nathenson, and L.J. Patrick Muffler

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Eruption column of the May 22, 1915, eruption of Lassen Peak viewed from downtown Red Bluff, California.

Summary

The Lassen region of the southernmost Cascade Range is an active volcanic area. At least 70 eruptions have occurred in the past 100,000 years, including 3 in the past 1,000 years, most recently in 1915. The record of past eruptions and the present state of the underlying magmatic and hydrothermal systems make it clear that future eruptions within the Lassen Volcanic Center are very likely. Although the annual probability of an eruption is small, the consequences of some types of eruptions could be severe. Compared to those of a typical Cascade composite volcano, eruptive vents at Lassen Volcanic Center and the surrounding area are widely dispersed, extending in a zone about 50 km wide from the southern boundary of Lassen Volcanic National Park north to the Pit River. This report presents a discussion of volcanic and other geologic hazards in the Lassen area and delineates hazards zones for different types of volcanic activity.

Owing to its presence in a national park with significant visitorship, its explosive behavior, and its proximity to regional infrastructure, the Lassen Volcanic Center has been designated a “high threat volcano” in the U.S. Geological Survey National Volcano Early Warning System assessment. Volcanic eruptions are typically preceded by seismic activity and ground deformation, and the Lassen area has a network of seismometers and Global Positioning System stations in place to monitor for early warning of volcanic activity.

         See also:
  • SIR 2012–5176–B, Eruption Probabilities for the Lassen Volcanic Center and Regional Volcanism, Northern California, and Probabilities for Large Explosive Eruptions in the Cascade Range
  • SIR 2012–5176–C, Lahar Hazard Zones for Eruption-Generated Lahars in the Lassen Volcanic Center, California
  • This report is also available in print from:

    USGS Information Services, Box 25286,
    Federal Center, Denver, CO 80225
    telephone: 888 ASK-USGS; e-mail: infoservices@usgs.gov

For additional information:
Contact CalVO
Volcano Science Center, California Volcano Observatory
U.S. Geological Survey
345 Middlefield Road, MS 910
Menlo Park, CA 94025
http://volcanoes.usgs.gov/observatories/calvo/

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Suggested citation:

Clynne, M.A., Robinson, J.E., Nathenson, M., and Muffler, L.J.P., 2012, Volcano hazards assessment for the Lassen region, northern California: U.S. Geological Survey Scientific Investigations Report 2012–5176–A, 47 p., 1 plate, Scale 1:200,000. (Available at http://pubs.usgs.gov/sir/2012/5176/a/.)



Contents

Executive Summary

Introduction

Types of Volcano Hazards and Effects of Volcanic Eruptions

Volcanism in the Lassen Region

Magma Beneath the Lassen Volcanic Center

Lassen Hydrothermal System

Seismicity and Ground Deformation

Volcano-Related Hazards in the Lassen Region

Volcanic Event Frequency, Probability and Magnitude

one plate


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