The rate at which a volcano extrudes lava is a key variable for tracking changes in volcano behavior, magma supply, and potential hazards to people and property. Locally, lava extrusion can have variable effects, from small-scale doming to large-scale changes in a landscape due to lava flows. Accurately measuring these changes, however, is often difficult because of infrequent satellite observations and sparse ground-based measurements.
To overcome this challenge, Arnold et al. used high-resolution radar satellite imagery to investigate both ground deformation and constructional topographic changes at El Reventador, one of Ecuador’s most active volcanoes. Using data collected from two missions, the German Aerospace Center’s TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X) and the Canadian Space Agency’s RADARSAT-2, the team analyzed differences in surface roughness during the volcano’s most recent eruptive phase, which began in 2012. They then used these results to map the extent and thickness of 39 new lava flows, whose bulk volume (through 24 August 2016) they estimate to be 56 million cubic meters.
The results show that this method is sensitive enough to document differences in the rate of lava extrusion, which is slowly decreasing at El Reventador. The method was also capable of detecting low-magnitude deformation of the volcanic edifice, including the intrusion of a small, vertical dike near the summit associated with the start of the eruptive phase.
The study demonstrates the tangible benefits of using radar imagery to supplement other measurements of changing topography in active volcanic settings. It also represents an important step forward in our understanding of the evolution of the ongoing El Reventador eruption and long-lived volcanic activity in general. (Journal Geophysical Research: Solid Earth, https://doi.org/10.1002/2017JB014580, 2017)
—Terri Cook, Freelance Writer