Shallow magma accumulation in the crust often results in slight movements of the ground surface that can be measured using standard land-surveying techniques or satellite geodesy. Volcano geodesy uses measurements of crustal deformation to investigate volcano unrest and to search for magma reservoirs beneath active volcanic areas.
Relative gravity measurements were made at 12 sites on Mount St. Helens and 4 sites far afield during the summers of 2010, 2012, 2014, and 2016. Positive residual gravity changes of 0.05–0.06 ± 0.01 mGal from 2010 to 2016—a sign of mass addition—remain at proximal sites after accounting for the effects of changes in Crater Glacier shape and mass. Modeling of the 2010–2016 monitoring data indicates mass addition in the volcano magma reservoir, the volcano conduit, and/or the shallow hydrothermal aquifer.
Sabancaya is the most active volcano of the Ampato-Sabancaya Volcanic Complex (ASVC) in southern Perú and has been erupting since 2016. The analysis of ascending and descending Sentinel-1 orbits (DInSAR) and Global Navigation Satellite System (GNSS) datasets from 2014 to 2019 imaged a radially symmetric inflating area, uplifting at a rate of 35 to 50 mm/yr and centered 5 km north of Sabancaya. The DInSAR and GNSS data were modeled independently. We inverted the DInSAR data to infer the location, depth, and volume change of the deformation source.
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