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GEOPHYSICAL RESEARCH LETTERS, VOL. 29, NO. 7, 1122, doi:10.1029/2001GL014205, 2002

Magmatic activity beneath the quiescent Three Sisters volcanic center, central Oregon Cascade Range, USA

Charles W. Wicks Jr.

U.S. Geological Survey (USGS), Menlo Park, CA, USA


Daniel Dzurisin

USGS, Cascades Volcano Observatory, Vancouver, WA, USA


Steven Ingebritsen

U.S. Geological Survey (USGS), Menlo Park, CA, USA


Wayne Thatcher

U.S. Geological Survey (USGS), Menlo Park, CA, USA


Zhong Lu

USGS, EROS Data Center, Raytheon, Sioux Falls, SD, USA


Justin Iverson

Dept. of Geological Sciences, Oregon State Univ., OR, Corvallis, USA


Abstract

Images from satellite interferometric synthetic aperture radar (InSAR) reveal uplift of a broad ∼10 km by 20 km area in the Three Sisters volcanic center of the central Oregon Cascade Range, ∼130 km south of Mt. St. Helens. The last eruption in the volcanic center occurred ∼1500 years ago. Multiple satellite images from 1992 through 2000 indicate that most if not all of ∼100 mm of observed uplift occurred between September 1998 and October 2000. Geochemical (water chemistry) anomalies, first noted during 1990, coincide with the area of uplift and suggest the existence of a crustal magma reservoir prior to the uplift. We interpret the uplift as inflation caused by an ongoing episode of magma intrusion at a depth of ∼6.5 km.

Published 11 April 2002.

Index Terms: 8434 Volcanology: Magma migration; 1208 Geodesy and Gravity: Crustal movements—intraplate (8110); 0933 Exploration Geophysics: Remote sensing.

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Citation: Wicks, C. W., Jr., D. Dzurisin, S. Ingebritsen, W. Thatcher, Z. Lu, and J. Iverson (2002), Magmatic activity beneath the quiescent Three Sisters volcanic center, central Oregon Cascade Range, USA, Geophys. Res. Lett., 29(7), 1122, doi:10.1029/2001GL014205.