Although most of the range is non-volcanic, portions at the western end near the Wrangell Mountains are volcanic. This region includes two major stratovolcanoes, Mount Churchill and Mount Bona, the latter being the highest volcano in the United States. West of the Saint Elias Mountains is the still-active Fairweather Fault, which is the northward extension of the Queen Charlotte Fault. The St. Elias range is a result of 10 million years of the North American tectonic plate pushing material up as it overrides the Pacific plate, then the material being worn down by glaciers.
The mountains are divided by the Duke Depression, with the shorter, more rounded Kluane Ranges to the east, and the higher Icefield Ranges to the west. Sub-ranges of the Saint Elias include the Alsek Ranges, the Fairweather Range, and the Centennial Range.