Geology

Sand and Glaciers

While no glaciers currently exist within the park, at least five major Pleistocene glaciations have been identified in Northwest Alaska. The greatest of these glacial events occurred during Illinoisian time when glaciers extended west to the Baldwin Peninsula. The two earlier glaciations, the Kobuk and Ambler glaciations, covered large areas of the Kobuk and Selawik valleys, as well as the drainages of the Baird Mountains. The three later glaciations were restricted to portions of the Schwatka Mountains, east of the park.

During the interglacial period between the Kobuk and Ambler glaciations, glacio-fluvial deposits on river bars and outwash plains were worked by strong easterly winds. The down-valley movement of large volumes of silt and sand created dune fields (eolian deposits) which cover an area of approximately 200,000 acres. Most of this dune area is currently vegetated by tundra and forest, except for the three active dunes - the Great Kobuk Sand Dunes, the Little Kobuk Sand Dunes and the Hunt River Dunes. These active dunes cover approximately 20,500 acres. The Great Kobuk Sand Dunes lie less than two miles south of the Kobuk River, immediately east of Kavet Creek, and the Little Kobuk Sand Dunes lie about five miles south of the Kobuk River, in the southeastern portion of the park. The hunt River Dunes are located on the south bank of the Kobuk River at the mouth of the Hunt River.

The Great Kobuk Sand Dunes display a complete and readily observable sequence of dune development, from the U-shaped, concave dunes with vegetative cover in the eastern portion of the field, to the crescent-shaped, unvegetated barchan  dunes, which stand over 100 feet in height, in the western portion. It is the largest active dune field in arctic North America.