Seeing the Earth Again for the First Time from Space: Zombie Volcanoes, Simultaneously Subsiding Volcanoes, and the Eruption that Canceled my Plane Flight
Matthew Pritchard, Cornell University
For centuries, measurement of the shape of the Earth (called the science of geodesy) was always time-consuming and frequently perilous because it required the observer to physically touch a point on the Earth's surface with a surveying instrument. Even with new technologies like the Global Positioning System (GPS), vast portions of the Earth remain infrequently monitored for movement. Recently, a new form of geodesy whereby image pairs can be compared to infer movements of the Earth's surface has rapidly developed. Called geodetic imaging, the synoptic aircraft or satellite images allow large regions to be surveyed without any human in the area. Imaging geodesy encompasses several methods including Interferometric Synthetic Aperture Radar (InSAR) that can image sub-centimeter deformation of the Earth's surface every 1-20 meters over areas spanning hundreds to thousands of kilometers. InSAR has allowed areas of the Earth's surface to be monitored for the first time. This presentation will highlight some of the discoveries, like the number of deforming volcanoes is 226 (from 44 in 1997). The number will continue to grow as data access increases -- there will be 12 SAR satellites by 2017, including the first satellites devoted to the technique with an open data policy. But our understanding is still catching up, and I highlight the challenges -- including understanding unusual features like “zombie volcanoes” and volcanoes that subside together when large earthquakes occur nearby.