Experimental simulations of explosive degassing of magma

Dynamics of explosive degassing of magma Observations of fragmenting twophase flows

Liquid explosions, generated by rapid egassing of strongly supersaturated liquids, have been investigated in the laboratory with a view to understanding the basic physical laX•sses operating during bubble nucleation a d growth and the subsequent behavior fthe expanding two-phase flow. Experimenkq are carried out in a shock tube and ,me monitored by high-speed photography and pressure trm•sducer...

Magma fracturing and degassing associated with obsidian formation: The explosive–effusive transition

Magma degassing during the Plinian eruption of Novarupta, Alaska, 1912

[1] We have modeled the nucleation and isothermal growth of bubbles in dacite from the 1912 Plinian eruption of Novarupta, Alaska. Bubble growth calculations account for the exsolution of H2O and CO2, beginning with bubble nucleation and ending when bubble sizes reproduced the observed size distribution of vesicles in Novarupta pumice clasts. Assuming classical nucleation theory, bubbles nuclea...

Influence of non-Newtonian rheology on magma degassing

Many volcanoes exhibit temporal changes in their degassing process, from rapid gas puffing to lava fountaining and long-lasting quiescent passive degassing periods. This range of behaviors has been explained in terms of changes in gas flux and/or magma input rate. We report here a simple laboratory experiment which shows that the nonNewtonian rheology of magma can be responsible, alone, for suc...

A theoretical model of the explosive fragmentation of vesicular magma

Recent experimental work has shown that, when a vertical column of rock under large pressure is suddenly depressurized, the column can ‘explode’ in a structured and repeatable way. The observations show that a sequence of horizontal fractures forms from the top down, and the resulting blocks are lifted off and ejected. The blocks can suffer secondary internal fractures. This experiment provides...