there is snow and ice all the year. the snow and ice starts to move down a valley that has been made by a fast-flowing stream. as the ice starts to slide down the mountainside, it does not flow around the rocks; it pushes the rocks out of the way. as a glacier moves, it picks up more ice and gets bigger and bigger. a big glacier cuts through the soil and softer rock of the valley and piles up the rocks on either side, or pushes them in front of it. when a big glacier melts, it leaves a valley of a deep u-shape. many valleys like this were 