Rocky Mountain National Park can be viewed as a marvelous outdoor geology text with special emphasis on glacial geology. Ice is a powerful sculptor of the natural environment, and glaciers- large masses of moving ice- are among the most powerful tools. While there are several small glaciers in the park, the time of massive glaciation in the park is past. We can still see the telltale marks of giant glaciers all over the park though.
As glaciers move, they pick up rocks, gravel, and sand. These rock fragments freeze into the glacial ice and serve as very effective "teeth" to help carve the landscape which they cross. Imagine chunks of granite being pressed down into the underlying material by tons of glacial ice. This mechanism can carve rock easily, and glacial grooves are the evidence.
As glaciers ebb and flow, they sometimes leave lateral moraines along their sides or terminal moraines at their ends. These moraines are like the beach lines you can sometimes see along lakes and indicate the highest level to which the glacier extended. They can be identified because they are poorly sorted (of a variety of different sizes) rocks. After some time they are covered with vegetation and are much less recognizable to the casual observer.
When the glacier finally melts, the rocks and debris it carried are released. They often form a thick layer called a valley bottom moraine, which can weather into deep, rich soil. The rock fragments are left in places far from where they originated, and are referred to by geologists as eratics (i.e. rocks out of place).
Rocky Mountain National Park has examples of many types of glacial features. You may want to try to find some on your next visit.