Rapid lake drainage: elastic blister dynamics with topography*

Geological processes such as subglacial flooding and magmatic intrusions are often modelled as blisters of fluid spreading beneath an elastic sheet. The behaviour of these blisters is determined almost entirely by contact line dynamics, with the interior of the blister remaining approximately hydrostatic. Previous work has described how curvature at the contact line causes the elastic sheet to peel upwards and hence leads to spreading. Here we show that the introduction of along-slope gravity can fundamentally change the dynamics by removing the jump in curvature at the upslope edge. This allows for a receding contact line and a new "translating" regime in which the main body of the blister moves downslope at approximately constant speed, leaving behind a thin trail of fluid. This allows the blister to move much further and faster than in the case where the evolution is determined entirely by spreading, and raises questions about the impact of basal topography and existing drainage networks on subglacial flooding beneath ice sheets.