Pacific Northwest Geodetic Array
Central Washington University

Three Sisters Volcano Joint GPS Occupation with USGS

Central Washington University's PANGA Geodesy Field Methods course. Campaign GPS measurements at Three Sisters Volcano in Oregon with USGS Cascades Volcano Observatory.

GPS Occupation Map
Campaign GPS Occupation Locations
KOKO and South Sister
KOKO and South Sister

Three Sisters in the central Oregon Cascade Range is a long-lived center of basaltic to rhyolitic volcanism producing rhyolite tephra, pyorclastic flows, lava flows and domes as recently as a thousand years ago. In September 1997, magamtic intrusion within the crust caused uplift of a broad area centered west of the South Sister summit.*

Mike Wickiup Plain
Mike Lisowski
Cold Fingers
Cold Fingers
South Sister
South Sister

Dzurian, Lisowski and Wicks of the U.S. Geological Survey combined GPS, leveling, and InSAR data to determine the temporal and spatial nature causing this uplift. By simultaneously inverting these datasets, the researchers calculate a decreasing inflation rate with a net increase in source volume of up to 42 million cubic meters at a depth of around 5km.*

Mesa Creek Station
Mesa Creek Station
Approach
Hiking In
Devil's Lake
Devil's Lake

PANGA has contributed to the GPS component of these investigations as part of our ongoing initiative to monitor natural hazards throughout the Pacific Northwest. Along with other geodetic datasets, GPS will refine understanding into to the mechanisms and future expansion of magmatic intrusion within this highly volatile volcanic area.

South Sister
South Sister
Packing Up
Packing Up KOKO
Mt. Hood
Mount Hood

*from: Dzurian, D., M. Lisowski, C. Wicks, Continuing inflation at Three Sisters volcanic center, central Oregon Cascade Range, USA, from GPS, leveling, and InSAR observations, J. Volcanol Geotherm Res, doi:101007/s00445-009-0296-4