Geologic formations of Cretaceous and Upper Jurassic sediments occur extensively throughout the Chugach Mountains. The Chugach Mountains are underlain by isolated masses of permafrost. The mountains of the southern half of the region are generally free of permafrost. The ecoregion was extensively glaciated during the Pleistocene epoch, and many glaciers remain. Features typical of glaciated terrain, such as artes, horns, cirques, U-shaped valleys, and morainal deposits in valleys and on lower hillslopes, are abundant.
Streams are short and swift, and headwatered in glaciers.
Lakes lie in ice-carved basins. Soils Most areas are covered by glaciers, ice fields, or rock outcrops. Where soil development has occurred, soils have formed in gravelly till and colluvium. Soils on steep ridges are shallow over bedrock. Dominant soils are Lithic Cryorthents, Andic Cryumbrepts, Pergelic Cryumbrepts, Typic Cryumbrepts, Typic Haplocryods, Andic Humicryods, Lithic Humicryods, and Typic Humicryods.