Transition From Open to Closed System Volcanism Through Sealing of the Conduit at Telica Volcano, Nicaragua

Telica volcano's recent eruptions are hypothesized to have been driven by a sealing system. The partial to complete sealing of the top of the volcanic conduit is thought to occur through the deposition of salts and silicate minerals from hydrothermal fluids, essentially moving the volcano from an open to a closed system within an inter-eruptive period (~4 years). To study this transition, we use a wide range of data sets including gas flux monitoring, broadband seismometer, deformation from cGPS, crater incandescence, and camera monitoring of the volcano's activity. The formation of the seal is observed indirectly by a decrease of the measured gas flux in the volcanic plume, a decrease in LF seismicity that indicates a shallow accumulation of gas in the conduit, as well as the deformation of the volcanic edifice due to the increase in pressure from gas accumulation. This sealing process would then explain the geodetic, seismic, and degassing signals observed at Telica from cGPS, broadband seismometer and SO2 gas flux respectively. Additionally, there is evidence of injection of a small volume of viscous magma in the conduit from observations of the crater floor and ash analysis. This input of magma then contributes to the sealing of the conduit, and the deformation observed at the Telica. The increase of pressure due to sealing of the system and rising magma eventually leads to a phreatic eruption. Understanding this transition between an open to closed system over time is important in terms of understanding Telica's eruptive processes, as well as gaining a better understanding of how this transition could manifest at other volcanoes, albeit on a different time scale.