Volcano Watch: Inflating volcanoes or cloudy data? Discerning deformation from noise with InSAR

  • USGS images by Megan McLay “Noisy” InSAR interferogram examples covering the Island of Hawaiʻi. (A) shows data that spans 12 days. This InSAR image show similar concentric ring patterns over both Mauna Loa and Mauna Kea. At first glance this might indicate deformation at both volcanos to the untrained eye, but the most likely reason for these colorful concentric ring patterns is atmospheric noise. (B) is another example of an InSAR interferogram with heavy atmospheric noise; this one has a 30-day difference from each SAR image. Some slight (less than a fraction of an inch/mm range) deformation on Mauna Loa and the Southeast Rift Zone of Kīlauea is visible in these images, yet still hard to discern from the atmospheric noise. Notice that the lower forested slopes of the island are blank. This is because heavy tree cover also causes errors in the interferograms.

Satellites have become one of the fundamental tools used to monitor active volcanoes. They allow us to monitor volcanoes that are otherwise hard to access and provide perspectives that are not possible to get from the ground. Satellites orbiting the Earth can provide normal “pictures” of a place, but can also provide thermal images, measure amounts and types of gases, changes in gravity, and topography.