Cape Krusenstern's Geology: 114 Beach Ridges and 5,000 Years of Arctic History

At Cape Krusenstern, the coast itself is an archive. Beside Krusenstern Lagoon runs a succession of 114 lateral beach ridges, and the archeological sites along them record the history of communities going back 5,000 years. Sites on the bluff behind the ridges may be as much as 9,000 years old.

A rock outcrop in Cape Krusenstern National Monument. From the National Park Service Geodiversity Atlas.

The monument

Barrier islands, lagoons, wetlands, coastal plain and beaches make up the landscape, and provide habitat for fish, marine mammals and migratory birds.

The rocks beneath

The bedrock is mostly sedimentary, in three groups:

The youngest bedrock, in the east-central part of the monument, is the Cretaceous Okpikruak and Fortress Mountain Formations. On top of it all lie younger Cenozoic deposits: Pleistocene terrace deposits, Pleistocene to Holocene river sediments (alluvium), and Holocene beach deposits.

Tundra and rolling hills in Cape Krusenstern National Monument. From the National Park Service Geodiversity Atlas.

Where the detail lives

Geodiversity is the full variety of a park's geologic and soil resources and processes: rocks, minerals, sediments, fossils, landforms and the physical processes that shape them. The NPS Geodiversity Atlas, a product of the Geologic Resources Inventory, supports education, geoconservation and management that treats the living and non-living parts of an ecosystem together. The inventory produces digital geologic maps and reports for more than 270 natural resource parks, and a Soil Resources Inventory has been completed for Cape Krusenstern. Both are in the NPS DataStore.

Sources

Based on "NPS Geodiversity Atlas—Cape Krusenstern National Monument, Alaska," National Park Service, a work of the United States government in the public domain. It cites Giddings and Anderson (1986) and the National Park Service (2016).