Volatiles drive volcanic eruptions. The flow of magma and gas through shallow volcanic conduits is thought to produce very long period seismic signals (VLPs). At Stromboli Volcano, Italy (the type volcano for strombolian explosions) and other basaltic volcanoes worldwide, VLPs have been modelled as gas slug flow through the conduit followed by an explosion when the slug bursts at a free surface. However, these interpretations do not account for variable crystal content. Here we show that the standard 'slug' model does not hold during a period of intense study at Stromboli in 2018. We compare the timing and characteristics between two repeating VLP families and explosions at the surface, as indicated by acoustic data. We argue that VLPs are generated when gas bubbles interact with and move into a semipermeable plug in the uppermost portion of the conduit, which acts as a mechanical filter for gas transport.

Event held on Zoom, accessible via this link: https://bristol-ac-uk.zoom.us/j/98668186683

Speaker website: Kathleen F. Mckee