Glaciers are enormous sheets of ice that move slowly over the land. They form when more snow falls in the winter than melts in the summer. Glaciers can form in high mountain valleys because it is cold due to the elevation. Continental glaciers form near the poles because it is cold due to the latitude. As the snow becomes deeper, the weight squeezes the snow below into ice. Once the ice becomes 100 meters thick, it can move. These huge sheets of ice acts as giant bulldozers. They move rocks and sediments. Once a glacier reaches the edges of a continent, it breaks off into icebergs.