What's moving at Yellowstone? The 1987 crustal deformation survey from GPS, leveling, precision gravity, and trilateration



The Yellowstone Plateau of northwestern Wyoming (Figure 1) is the site of one of the world's greatest displays of hydrothermal activity (geysers, hot springs, and fumeroles). In the past 2 million years, three catastrophic volcanic eruptions have expelled more than 3500 km3 of rhyolitic ash flow tuffs forming three gigantic calderas. Intensive earthquake activity, including the Intermountain region's largest historic earthquake, the 1959, ML 7.5, Hebgen Lake, Montana, event and extensive earthquake swarms in and around the Yellowstone caldera characterize the seismicity. Heat flow of ∼1500 mWm−2, in excess of 30 times the continental average, and historical crustal deformation of up to 1 m of uplift reflect the contemporary dynamics of this active volcano-tectonic region.