Beginning in 2004, the Yellowstone caldera, extending 40 kilometers by 60 km (25 miles by 37 miles) in Yellowstone National Park, northwestern Wyoming, began a period of accelerated uplift, with rates of uplift as high as 7 centimeters per year, or 2.8 inches per year. From 2006 to 2009 the uplift rate slowed.
Global Positioning System (GPS) and interferometric synthetic aperture radar (InSAR) ground deformation measurements described by Chang et al. show that in the northern caldera uplift decreased from 7 cm/yr in 2006 to 5 cm/yr in 2008 and 2 cm/yr in 2009. In the southwestern portion of the caldera, uplift decreased from 4 cm/yr in 2006 to 2 cm/yr in 2008 and 0.5 cm/yr in 2009, demonstrating a spatial pattern of ground motion decrease from southwest to northeast along the caldera.
What caused this extraordinary uplift, and why has the uplift slowed? On the basis of models the authors suggest that the uplift since mid-2004 was caused primarily by a growing magma reservoir 7 to 10 km (4 to 6 mi) below the caldera. The magma reservoir has been expanding, but the expansion rate decreased 60 percent between 2006 and 2009.
The slowing expansion of the magma reservoir, along with release of stress by extensive earthquakes that occurred in clusters, called swarms, in 2008 and 2010, can account for the slowing uplift, the researchers suggest. Continued monitoring of ground deformation in the Yellowstone caldera could be useful for understanding volcanic physics and the related volcano and earthquake hazard in the region.
Source: Geophysical Research Letters, doi:10.1029/2010GL045451, 2010
Title: An extraordinary episode of Yellowstone caldera uplift, 2004 to 2010, from GPS and InSAR observations
Authors: Wu-Lung Chang: Department of Earth Sciences, National Central University, Jhongli, Taiwan;
Robert B. Smith, Jamie Farrell, and Christine M. Puskas: Department of Geology and Geophysics, University of Utah,Salt Lake City, Utah, USA