Technologies track surface changes at Yellowstone.

Summer geology intern Mindy Juergenson climbs over downed lodgepole pine trees killed in the fire of 1988 as she packs a GPS station out of the field (inset). Nine temporary stations are deployed each April/May and retrieved in October/November. The temporary stations supplement a network of permanent stations that record ground deformation data year-round. GPS is used along with InSAR (Interferometric Synthetic-Aperture Radar) to monitor volcanoes in the western US (Aleutians, Cascades, Hawaii, Yellowstone, Long Valley) and around the world. This radar interferogram (larger image) shows the ground deformation pattern at the Yellowstone caldera during 2004-2006. The color bands ("fringes") are akin to contour lines on a conventional topographic map. Here, they represent about 6 inches (15 cm) of ground uplift in the northeast part of the caldera.