The most striking scenery in Rocky Mountain National Park was created by glaciers. Broad valleys, deep cirques and spectacular cliffs are all evidence of glacial erosion. If the climate cools, the summers will no longer be warm enough to melt winter snows. If this happens, the snow accumulates, compacts under the weight, and forms an icy block called a glacier. Glaciers are commonly 1000ft or more thick in places.
Glaciers like to flow downhill.
As a glacier moves, it picks up loose boulders and carries them. These boulders scour the underlying rock, grinding it away much like sandpaper on wood. After thousands of years, large gorges are carved out as rock is removed by a glacier. The rocks and boulders a glacier carries is called till. Snow blown over the Continental Divide collected in east and north-facing valleys and formed glaciers.