Cape Krusenstern

National Monument

Alaska

Cape Krusenstern National Monument, Alaska

Cape Krusenstern National Monument is a coastal plain dotted with sizable lagoons and backed by gently rolling limestone hills. Treeless, the cape gives you the feeling of being able to see forever. Cape Krusenstern's bluffs and its series of 114 beach ridges record changing shorelines of the Chukchi Sea. They also record in time sequence an estimated 6,000 years of prehistoric human use of this coastline. In summer a tremendous show of wildflowers colors the beach ridges and nearby hills. Huge numbers of birds come to the coastal area for nesting. Some archeological resources here are older than well-known remains of ancient Greek civilizations on the Mediterranean Sea. Shifting sea ice, ocean currents, and waves have formed-and continue to form- spits and lagoons possessing important scientific, cultural, and scenic values. In fall, migrating waterfowl use the lagoons as feeding and staging areas. The broad plain between the hills of the cape and those in the northern section of the monument is the tundra-covered bed of a huge glacier formed 250,000 years ago-and the former course of the Noatak River.

Geology

The geological framework of the northwest Alaska region was set by the late Paleozoic era, 600 million years ago. During the Triassic period, 225 million years ago, the site of the present Brooks Range was stabilized, and limestone and chert were formed. The process of mountain building began during the mid Jurassic period. 135 million years ago the land was intensely folded and faulted, and the existing east west fault trends within the area were established. In late Miocene time, 25 million years ago, seas flooded much of the formerly dry area of the Chukchi zone but retreated somewhat to form a land bridge between Siberia and Alaska. This land area was again overlain by seas about 4 million years ago and remained so until approximately one million years ago. The ice advances that occurred during Pleistocene time, one million years ago, caused a substantial drop in sea level and a consequent exposure of the land mass known as Beringia. The last retreat of the glaciers established the present sea level approximately 4,500 years ago.

Bedrock geology of the inland area north and east of the Krusenstern Lagoon includes rocks from Precambrian to Devonian times. Limestone, dolomite, chert, and phyllite are greatest in abundance. The southern extension of the Mulgrave Hills within the monument, known as the Tahinichok Mountains, contains dolomite, sandstone, shale, and limestone from the Devonian to Mississippian periods. Glaciofluvial deposits are found over an area between the Noatak River to Kotlik Lagoon and between the Kilikmak and Jade Creek drainages. Within the monument this area was twice affected by glacial advances during the Pleistocene epoch. The first glacial advance occurred during the middle Pleistocene time (Hopkins, 1977). This event occurred between 250,000 and 1,250,000 years ago. The second, and more recent, glaciation correlates with the Illinoisan glaciation of the central United States and occurred between 125,000 and 250,000 years ago. During both periods of glaciation large glaciers extended down the Noatak River drainage, across the lowland area east of the Kotlik Lagoon, and left the present glaciofluvial deposits. The monument has not been glaciated for approximately 125,000 years. A unique feature within the monument is a recognizable Illinoisan glacial esker or gravel ridge marking the bed of a subglacial stream (Hopkins 1977). An esker of this age (over 100,000 years old) is considered rare.

The coastal area of the monument north of Kotzebue Sound is a beach ridge plain, which has received sediments deposited by longshore currents over the last several thousand years. The primary purpose of the Cape Krusenstern National Monument is to protect and interpret this beach ridge complex, which contains archeological sites depicting every known cultural period in arctic Alaska over a 6,000 year period.

Soils

The major soil types associated with the monument include the upland or mountain slope soils and those associated with the lowland areas nearer the coast. The lower slopes of the western Igichuk Hills and the Mulgrave Hills are covered with poorly drained, gravelly or loamy soils with a surface layer of peat. Depth to permafrost is variable. The upper slopes of these hilly areas have well drained gravelly or loamy soils with a deep permafrost table.

Along the coastline of the monument and flanking Krusenstern, Kotlik, and other major lagoons are marine and alluvial deposits that form beaches, spits, and deltas. Soils of lowland areas along the coast are poorly drained, with a surface layer of fibrous peat and a shallow permafrost table. The peat layer ranges from 20 to 61 cm in depth.

Soil temperatures at nearby Kotzebue at a depth of 30 range from a high of 4°C during July and August to less than -9°C during most of February and March (Selkregg 1975). Because of the lag time between summer temperature highs near the surface and those at greater depths, the maximum depth of soils at more than -1.1°C is reached in Kotzebue in December.

Permafrost plays an important role in the topographic development and appearance of lands within the monument. The lowland areas of the monument are underlain by thick continuous permafrost. Permafrost can reach depths of 610 m, but generally reaches a maximum depth of 427 m within the inland portions of the monument. At nearby Kotzebue permafrost depths are generally less than 73 m because of saltwater intrusion at that depth (City of Kotzebue 1971).

A variety of permafrost features are evident within the monument, particularly in the lowland areas. These include thaw lakes, ice wedge polygons, pingos, frost mounds, and solifluction lobes. Many of these features are caused by localized melting of ground ice, resulting in thermokarst formation.

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A general park map is available on the park's map webpage.

For information about topographic maps, geologic maps, and geologic data sets, please see the geologic maps page.

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A geology photo album has not been prepared for this park.

For information on other photo collections featuring National Park geology, please see the Image Sources page.

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Currently, we do not have a listing for a park-specific geoscience book. The park's geology may be described in regional or state geology texts.

Please visit the Geology Books and Media webpage for additional sources such as text books, theme books, CD ROMs, and technical reports.

Parks and Plates: The Geology of Our National Parks, Monuments & Seashores.
Lillie, Robert J., 2005.
W.W. Norton and Company.
ISBN 0-393-92407-6
9" x 10.75", paperback, 550 pages, full color throughout

The spectacular geology in our national parks provides the answers to many questions about the Earth. The answers can be appreciated through plate tectonics, an exciting way to understand the ongoing natural processes that sculpt our landscape. Parks and Plates is a visual and scientific voyage of discovery!

Ordering from your National Park Cooperative Associations' bookstores helps to support programs in the parks. Please visit the bookstore locator for park books and much more.

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For information about permits that are required for conducting geologic research activities in National Parks, see the Permits Information page.

The NPS maintains a searchable data base of research needs that have been identified by parks.

A bibliography of geologic references is being prepared for each park through the Geologic Resources Evaluation Program (GRE). Please see the GRE website for more information and contacts.

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