... the obstacle protruding into the base of the ice mass causes an increase in pressure within the ice on the upstream face of the obstacle. thus increasing the rate of ice deformation around the obstacle, allowing the ice mass to smoothly pass over or around the object. (which can form a roche moutonee) Another process that controls the flow of a glacier is a process called sub glacial bed deformation. This is where lose sediment at the bed of the glacier moves enabling the glacier to move more freely over the bed. In order to do this the subglacial bed has to be a warm based glacier, i.e. the glacier has to have a film of melt water at the base. The deformation occurs when the water pressure in the pores or spaces between the sediment grains increases sufficiently to reduce the resistance between the other grains. This allows the sediment ...

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