Harnessing the Full Potential of Gravity: Magma Loss and Recharge at Sierra Negra Volcano From Joint Modeling of Gravity and Deformation Data

Dataset A major challenge in volcano geodesy lies in constraining how much magma is storedbeneath a volcano during episodes of unrest. Sierra Negra, a large shield volcano in the Gal´apagos Islands, has a history of frequent activity. To understand the processes leadingto and controlling its 2018 eruption, volcanologists measured changes in surface deformationand in gravity between 2018 and 2019. By combining the two types of data,it was possible to estimate how much magma had moved from the volcano’s chamber andhow much has since been replenished. About 880 billion kilograms of magma were lostby the magma reservoir in 2018, matching the erupted volume. From late 2018 to 2019,around 180 billion kilograms were added back, and a similar amount was recharged be-tween2019 and 2022. This slow, tapering refill points to a roughly ten-year time scalefor a complete refill of the magma chamber, setting a lower bound for the timing of futureeruptions.