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Kobuk Valley

National Park

Alaska

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sand dunes at kobuk valley
Kobuk Valley National Park, Alaska

Kobuk Valley
Kobuk Valley National Park is also mountain enclosed-by the Baird and Waring mountains. Major natural features that the park protects include

  • the central section of the Kobuk River,
  • the 25-square-mile Great Kobuk Sand Dunes, and
  • the Little Kobuk and Hunt River dunes.
Additional dunes that have been stabilized by vegetation now cover much of the southern portion of the Kobuk Valley. Sand created by the grinding action of ancient glaciers has been carried to the Kobuk Valley by winds-westerly in summer and easterly the rest of the year-and by water. River bluffs composed of sand and standing as much as 150 feet high, hold permafrost ice wedges and the fossils of Ice Age mammals. Up to 1,500 feet wide, the placid Kobuk River falls a mere two to three inches per mile. Its valley provides important fall and winter range for the western arctic caribou herd. Bands of bulls and cows may be seen here from late August through October as they migrate across the Kobuk River on their extensive annual migrations. Native people have lived along the Kobuk for at least 12,000 years. Their history is best recorded at the Onion Portage archeological site. The Salmon River, within Kobuk Valley National Park, is classified as a national wild and scenic river.

Geology

Three general landscape types exist within Kobuk Valley National Park: the Baird Mountains, the Waring Mountains, and the Kobuk Valley lowlands (floodplain and terraces). The Baird Mountains are a western extension of the Brooks Range. The Baird Mountains separate the Noatak and Kobuk river drainages. They rise abruptly from the lowland on the south to heights of 2,500 to 4,757 feet (762 to 1,450 m). The Baird Mountains consist primarily of Paleozoic sedimentary and older metamorphosed rocks that have been thrust faulted and folded. Rock types are shale, conglomerate, sandstone, and metamorphosed limestone. On the southern flanks of the Baird Mountains, within the park, sediments metamorphosed into phyllite and schist are found. Jurassic to Permian volcanic and intrusive rocks are also present. The Waring Mountains, to the south of the Kobuk River, are broadly folded, northeast trending mountains primarily of Cretaceous sedimentary rock. Rock types include graywacke, sandstone, siltstone, shale, and conglomerate. The peaks of this range are generally less than 1,998 feet (609 m) high.

The Kobuk River runs through the lowland between the Baird Mountains and Waring Mountains. This area is largely covered by glacial drift and alluvial deposits, including clayey till , outwash gravel, sand, and silt. The underlying bedrock of the lowlands is composed of Cretaceous sedimentary rocks such as shale, sandstone, siltstone, conglomerate, and graywacke.

Although there are currently no glaciers 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 and 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, which cover an area of approximately 348 square miles (90,000 ha). 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 32 square feet (8,300 ha). The Great Kobuk Sand Dunes lie less than 1.9 miles (3 km) south of the Kobuk River, immediately east of Kavet Creek. The Little Kobuk Sand Dunes lie about 5 miles (8km) 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 across from 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 brachan dunes, which stand over 98 feet (30 m) high, in the western portion. It is the largest active dune field in arctic North America.

Lowland areas in the Kobuk River drainage are underlain by discontinuous permafrost with a maximum depth to its base of 387 feet (118 m). The Baird Mountains to the north are underlain by continuous permafrost, while the Waring Mountains to the south have thin to moderately thick permafrost. A variety of permafrost features are evident within the park. These features can be collectively referred to as "thermokarst topography," and include thaw lakes, ice wedges, polygons, pingos, frost mounds, and solifluction lobes. Ice wedges form when freeze/thaw cycles leave cracks for water to seep into. The water then freezes and forms an ice wedge. Polygons and pingos are formed from intersecting ice wedges.

Numerous large mineral deposits occur about 30 miles (48 km) to the east of the park in the vicinity of Cosmos Mountain and the Schwatka Mountains. Mineral terranes occur in the park through most of the Baird Mountains. The Salmon and Tutuksuk River watersheds are reported to have unusual (anomalous) concentrations of copper, lead, and zinc. A mineral terrane thought to be favorable for the occurrence of nickel, platinum and chromium deposits, runs along the base of the Baird Mountains, from about the center of the park, east along the base of the Schwatka Mountains. Despite the known or suspected mineral terranes that occur within the park, no significant mineral deposits have been identified in the park (AEIDC 1979 and 1982).

Jade is mined on the southern slopes of the Jade Mountains to the east of the park. Jade boulders are removed from the surface of talus slopes and are transported during the winter to the Kobuk River, where they are stockpiled to be taken by barge to Kotzebue after breakup. The boulders are cut and the jade is fashioned into jewelry and other items in Kotzebue.

Thin seams of subbituminous and bituminous coal (generally less than 2 feet thick) occur along the Kobuk River, between the village of Kiana and the Pah River, 60 miles (96 km) east of the park. Small outcrops of coal can be seen along the Kobuk River between Trinity Creek (about 4 miles downstream from the park's western boundary) and the Kallarichuk River within the park. Coal deposits have also been reported along a tributary at the Kallarichuk River.

Soils

Soils on the higher slopes of the Baird Mountains consist of thin layers of highly gravelly and stony loam. Where soils accumulate in protected pockets on steeper mountain slopes, they support mosses, lichens, and some dwarf shrubs. Soils on the broad lowlands within the park are generally poorly drained, with a peaty surface layer of variable depth and a shallow depth to permafrost. Texture within these soils varies from very gravelly to sandy or clayey loam.

An area of approximately 348 square miles (90,000 ha) south of the Kobuk River is composed of well drained, thin, strongly acidic soils. These are vegetated and unvegetated sand dune fields. The unvegetated Great Kobuk and Little Kobuk sand dune fields are comparable in soil type and texture to the vegetated portions of the dune fields, but they are rated as having high erosion potential due to scarcity of vegetation. The floodplains of the Kobuk River and its tributaries, including the Hunt, Akillik, and Salmon rivers, are characterized by silty and sandy sediments and gravel. Soil erosion along the banks of the Kobuk River can be significant. Most bank erosion occurs during spring breakup when high volumes of water and ice scour the riverbanks and carry sediment downstream. In places where river water comes into contact with permafrost in river banks, thermal erosion can occur. Additional erosion can occur during high precipitation in the summer months. Along the Kobuk River evidence of the erosion and slumping of sandy riverbanks is readily observable at numerous locations.



park maps subheading

A park map is not available.

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

photo album subheading

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.

books, videos, cds subheading

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.



geologic research subheading

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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NPS Geology and Soils Partners

NRCS logoAssociation of American State Geologists
NRCS logoGeological Society of America
NRCS logoNatural Resource Conservation Service - Soils
USGS logo U.S. Geological Survey

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For resources and information on teaching geology using National Park examples, see the Students & Teachers pages.
updated on 01/04/2005  I   http://nature.nps.gov/geology/parks/kova/index.cfm   I  Email: Webmaster
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