From Alaska to New Mexico, the Rockies are one of the great mountain belts of the world--caused by tectonic forces of the Pacific Plate pushing against the North American continent. They have formed as the earth's continental crust has been shortened under pressure--by around 1 inch a year. What's more, they are still rising and they are still young in geologic terms: when the dinosaurs roamed the Earth they had not even started to form.