An analytical model for gas overpressure in slug-driven explosions:insights into Strombolian volcanic eruptions

摘要: Strombolian eruptions, common at basaltic volcanoes, are mildly explosive events that driven by a large bubble of magmatic gas (a slug) rising up the conduit and bursting surface. Gas overpressure within slug governs explosion dynamics vigor is main factor controlling associated acoustic seismic signals. We present theoretical investigation based on magma-static geometric considerations develop set equations can be used to calculate in when it bursts, length burst, depth which burst process begins. find controlled two dimensionless parameters: V', represents amount slug, A', thickness film magma falls around slug. Burst increases nonlinearly as V' A' increase. consider eruptive scenarios: (1) "standard model," remains confined vent during expansion, (2) " overflow expansion with lava effusion, occasionally observed field. higher for model 1.2-2.4. Applying our typical eruptions Stromboli, we transition from passive degassing occurs slugs volume >24-230 m(3), depending viscosity diameter, (with 100-1000 m(3)) has an internal pressure 1-5 bars 13-120 m. compare predictions field data Stromboli low-energy puffers," violently 5 April 2003 paroxysm. consistent observations across this broad spectrum styles, suggesting slug-driven mechanism; propose paroxysms unusually (large V').