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