This magnificent range was created several hundred million years ago when two tectonic plates collided. Mountains have two separate precipitation patterns. The side toward the ocean is called the leeward side and this area gets most of the precipitation. The continental side is in what is called the rainshadow. This area receives much less rain.
Mountains also have different vegetation types depending on the slope of the mountain.
North-facing slopes receive the least direct sunshine and have shallow active layers. The trees here are primarily mixed black spruce and paper birch. The south-facing slope gets more direct sunlght and experiences better drainage due to the thicker active layer. There is less permafrost, which better suits aspen and white spruce. This is because of its massive size and its ability to create its own weather system, which sometimes enshrouds Denali in a blanket of clouds.