Subglacial cavitation
= Subglacial cavitation
A <water>-filled cavity opens where the normal contact <pressure> behind a bed obstacle would otherwise fall below subglacial <fluid pressure>[water pressure]. Reduced <effective pressure in subglacial drainage> enlarges cavities and changes the resisting contact geometry. For a fixed bounded-slope bed, the basal shear stress is bounded by a bed-dependent multiple of effective <pressure>; a sliding curve may saturate or weaken as cavities grow.