Gravity currents and solitary waves

Island volcanoes can initiate large tsunamis when pyroclastic flows hit the surrounding sea. The detailed dynamics and thermodynamics are complicated but the crucial feature is that of a descending dense current passing through one fluid (the atmosphere) and meeting another fluid (the sea). In this paper, laboratory and numerical experiments will be described which elucidate the principal dynamical phenomena and show that, if the density of the descending current is greater than that of the lower layer, large waves are very efficiently initiated. These waves approximate solitary waves closely.