Meltwater on glacier. View of meltwater nearly filling a large crevasse on top of the Columbia glacier, Alaska, USA. Crevasses are formed by parts of the ice of the glacier moving at different rates, cracking the surface. This typically happens as the ice on the sides of a glacier moves more slowly than the ice at the centre. When the glacier moves into a wider area, the sides flow outwards, which also causes crevasses to form. Meltwater is the water formed by the melting of ice on top of the glacier. There is usually a large amount of sediment in suspension in the water as well.