抄録
We investigate the influence of terrain on the slow spreading of isothermal lava by numerically solving initialvalue problems for a Bingham fluid. Under the lubrication approximation, systematic computation is carried out for two types of terrains: an inclined channel of finite width and a hill on a sloping base. The transient evolution and the final extent of lava are calculated for a dry bed. In the open channel the effects of bank steepness, Bingham parameter, and the total volume on the final extent of spreading are examined in detail. A simple formula is found by synthesis to relate the final elongation ratio of the deposit to these factors. For a hill on an inclined base, both symmetrical and asymmetrical spreading from a hillside are studied. The transient motion of the lava flow is found to follow essentially the direction of local path of steepest descent.
