ИСТИНА

Several types of lava dome morphology can be distinguished depending on the flow rate and the rheology of magma. At an endogenous regime, magma is embedded inside the dome and fresh magma is not extruded on the surface; vice versa, at an exogenous regime, a fresh lava is extruded, and a lava obelisk is of particular interest. Sometimes obelisks reach hundreds of meters in height before they collapse. We present models of magma extrusion on the surface and lava dome evolution to analyze morphology of the domes. For this aim, we consider a flow of a Newtonian and non-Newtonian viscous inhomogeneous incompressible fluid in the field of gravity. The flow is described by the Navier-Stokes equations, the continuity equation, the transport equation of a two-component incompressible fluid, the heat conduction equation, and the rheological law. The lava viscosity in our models depends on the crystals concentration, temperature, and the rate of shear deformation. We show that the morphology of the domes depends on the characteristic time of crystal growths in the magma and on the rate of magma extrusion. In this case, obelisks are formed at a small value of the characteristic time of growth of crystals and/or low extrusion rates. At high values of the characteristic time and high extrusion rates, magma spreads over the surface after an eruption.