Experimental simulations of explosive degassing of magma

摘要: Explosive flows of strongly gas-supersaturated liquids have been investigated experimentally in two different configurations to simulate conditions in violent volcanic eruptions. i) Decompression water saturated with dissolved C0_2 at pressures up to 0.7 MPa causes explosive bubble growth and foaming. The large volume increase accelerates the two-phase mixture upward velocities as 14 m/s nearly constant accelerations up more than 200 g. Constant acceleration implies that the bubble rate is proportional t^(2/3), measurably larger t^(1/2) law expected for diffusive spherical bubbles. ii) Rapid mixing concentrated K_2CO_3 and HCl solutions generates CO_2 supersaturated a few MPa. In this case, reaction and degassing generate an increasingly accelerating flow until reactants become depleted peak about 100g 45 m/s. both experiments rapid expansion foam fragment into heterogeneous spray. experimental are comparable volcanic terms of decompression ratio, velocities, range scales present. The cause strong extensional strain longitudinal deformation of foam. Tube pumice major component Plinian deposits ignimbrites, and preserves evidence these conditions.