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Release : 1989
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We have adapted computer codes that provide such solutions to study explosive volcanic phenomena. These fully nonlinear conservation equations are cast in two-dimensional cylindrical coordinates, which with closure equations comprise 16 equations with 16 unknown variables. Solutions for several hundred seconds of simulated eruption time require two to three hours of a Cray-1 computer time. Over 100 simulations have been run to simulate the physics of highly unsteady blasts, sustained and steady Plinian eruptions, fountaining, column eruptions, and multiphase flow of magma in lithospheric conduits. The unsteady-flow calculations show resemblance to shock-tube physics with propagation of shock waves into the atmosphere and rarefaction waves down the volcanic conduit. Steady-flow eruption simulations demonstrate the importance of supersonic flow and over pressure of erupted jets of tephra and gases in determining whether the jet will buoyantly rise or collapse back to the earth as a fountain. Flow conditions within conduits rising through the lithosphere determine eruptive conditions of overpressure, velocity, bulk density, and vent size. Such conditions within conduit systems are thought to be linked to low-frequency, sustained seismicity known as volcanic tremor. These calculations demonstrate the validity of some analytical eruption calculations under limited conditions. 31 refs., 10 figs., 1 tab.