Subsidence of the lava flows emitted during the 2012–2013 eruption of Tolbachik (Kamchatka, Russia): Satellite data and thermal model

International audienceWe estimated the subsidence rate of the lava flow formed during the 2012–2013 eruption of Tolbachik volcano from satellite radar interferometry with using Sentinel-1 satellite images between 2017 and 2019. The maximum subsidence values were 285 mm/yr in 2017, 249 mm/yr in 2018, and 261 mm/yr in 2019. The subsidence rate increases with the flow thickness. This trend is observed for most of locations except a small area in the vicinity of the active vent where the subsidence is anomalously high. We show that the main observed trend can be well explained by a thermal compaction with a 1D mathematical model that takes into account the latent heat of crystallization, temperature dependences of physical parameters (heat capacity, thermal conductivity, density), temperature dependence of crystal concentration in the melt volume, and the percentage of uncrystallized material (glass or melt), porosity and lava layer formation rate. The much faster subsidence rates observed close to the vent can be explained by contraction of buried lava tubes that is not accounted in the thermal model