Dynamics and destruction of volcanic bombs at underwater volcanic eruption

In this paper, the motion and destruction of volcanic bombs in a liquid medium at underwater volcanic eruption are studied. The equations determining the time of their motion until full braking is achieved in a water column and the corresponding depths are obtained. Two possible mechanisms of volcanic bomb destruction are examined. The first is based on the influence of the non-homogeneous temperature field on the bomb stress-strain behavior. A test problem of the stress-strain state of heated ball with lower temperature specified on its surface is considered as a model. The problem is solved in an elastic quasi-static formulation. The equations for main characteristics of the strain-stress state are obtained. Using the statistical theory of strength, which determines the dependence of the ultimate stress on the body size, the time to peak stresses at which the bombs are destroyed due to the temperature gradient is determined. The second mechanism is based on the effect of the drag force of the medium. A test problem of the cylinder motion in the direction perpendicular to its axe is considered as a model. The problem is solved within the framework of the classical theory of elasticity on the assumption of plane strain state. Using the quasistatic formulation, the problem for determining stress state of the volcanic bomb resulting from the medium drag force is solved. The most probable areas for fracture initiation are detected. The contribution of possible quasistatic rotation of the bomb to its destruction is studied qualitatively.