Volcano Watch: How to interpret an interferogram

COSMO-SkyMed (CSK) Interferogram for the period from April 6 to June 2, 2019, covering Kilauea Volcano’s summit region. (Courtesy graphic/USGS)

HAWAII VOLCANOES NATIONAL PARK — Since the early 1990s, scientists have used radar satellites to map movement, or deformation, of Earth’s surface. Interferometric Synthetic Aperture Radar calculates the difference between two radar images acquired by an orbiting satellite taken at different times but looking at the same place on Earth. This difference is called an interferogram, and is essentially a map of surface deformation.