-When base of ice reaches pressure melting point, ice melts. Leaving a thin layer of water beyween ice and bedrock, allowing ice to slide down the hill as frictional drag is reduced.
-On 'upglacier' side of obstacle, pressure in ice build up sufficiently to cuase pressure-melting locally. The water formed trickles around and over obstacle, where it refreezes in normal pressure conditions on 'downglacier' side of obstacle. If ice temperature is below melting point, the process…