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geology fieldnotes title

Wrangell - St. Elias

National Park and Preserve

Alaska

cover of park brochure

park geology subheading
the tops of the mountains at Wrangell-St. Elias
Wrangell - St. Elias National Park and Preserve, Alaska

The Wrangell Mountains, which form much of Wrangell - St. Elias National Park and Preserve (WRST), are made up largely of numerous lava flows that have been erupted mostly from large broad volcanoes during the past 26 million years. This extensive volcanic terrain, which is called the Wrangell volcanic field, covers about 4,000 mile square (10,400 km2) and extends eastward from the Copper River Basin through the Wrangell Mountains, into the St. Elias Mountains of Alaska and the Yukon Territory of Canada.

The principal basement rocks on which the Wrangell volcanoes erupted are much older rocks and have had a complex geologic history. These rocks belong to what is referred to in the geologic literature as the Wrangellia terrane, which is part of an even larger group of exotic terranes - the Wrangellia composite terrane - that has been accreted to Alaska and the North American Continent during the past few hundred million years. On the basis of geophysical and fossil evidence, rocks of the Wrangellia terrane were formed in a tropical environment thousands of miles south of its present position. The Wrangellia terrane began as a volcanic arc about 300 million years ago, probably along the margin of an ancient North American continent. As arc-related volcanic activity waned, a rift developed between the arc and continent, allowing the eruption of thousands of cubic miles of basalt lava flows that flooded and filled the rift-formed basin. Subsequently, shallow warm seas inundated the land, depositing layers of marine limestone and other sediment on the volcanic rocks.

During the next 200 million years, the Wrangellia terrane was gradually transported northward, where it was welded to other terranes and eventually docked against western North America about 100 million years ago. It now forms a belt extending from southern Alaska to southern British Columbia. Subsequently, other terranes, such as those composing the Southern Margin composite terrane, have been carried northward and accreted to continental Alaska. The last terrane to arrive, the Yakutat terrane, docked about 26 million years ago, concurrent with, and partly responsible for the development of the Wrangell volcanic field.The Wrangells include exposed deformational structures that reflect at least three major episodes of mountain building. Over the entire area, rock units are folded, faulted, twisted and stretched, often in a spectacular manner (Shaine et al., 1973). Deformation occurs at all scales, recording the dynamic history of this landscape.

Physiography

The mountains in WRST are part of the Pacific Mountain System, a belt of parallel mountain ranges separated by intervening lowlands bordering the Pacific Ocean. Lowlands are extensive only in the region's center and along its western and northwestern fringes. Elsewhere, the lowlands are sandwiched between mountains and sea, or occur as narrow valleys and plateaus grading into uplands and serrated peaks (U.S. Department of the Interior, 1974). The coast of WRST borders the Chugach and St. Elias mountains. Terrain is varied, with beach and dune ridges running parallel to the coast and glacial moraines and outwash plains widespread. Elevated marine terraces as high as 800 feet above sea level are present inland. A couple of large fjords, Icy Bay and Disenchantment Bay, indent the otherwise straight coastline. The region can be divided into four physiographic provinces, see Table 1 (Warhaftig, 1965).

Snow, Ice and Glaciers

Glaciers are the dominate sculptor that has produced today's landscape in WRST. Today glaciers cover approximately 20 percent of the 13 million acres within the park and preserve (National Park Service, 1998a). The coastal Chugach and St. Elias mountains are virtually inundated by icefields covering about 4 million acres of which the 80-milelong Bagley Icefield is the longest (U.S. Department of the Interior, 1974). Seasonal ice and snow cover affects the characteristics of aquatic ecosystems. They control the amount of light reaching the unfrozen water beneath the ice (Prowse and Stephenson, 1986). Ice can also prevent gas exchange between underlying waters and the atmosphere and may commonly lead to depletion of dissolved oxygen and the build up of reduced gasses such as CO2, CH4 and H2S (Rouse et al., 1997). The processes accompanying ice formation during freeze-up and break-up have a wide range of effects on the bed, banks, and biota of lakes and rivers. These include frazil ice (aggregate of ice crystals formed in supercooled turbulent water) impact on fish and invertebrates, anchor ice growth, elevated water levels, channel blockage and increased scouring (Prowse, 1994).

Glacier ice is a metamorphic rock that consists of interlocking crystals of the mineral ice and owes its characteristics to deformation under the weight of overlying snow and ice. Snow that survives a year or more gradually increases in density until it is no longer permeable to air, at which point it becomes glacier ice. Although now a rock, such ice has a density of about 0.9 g/cm3 and will float in water (Skinner and Porter, 1992). Glaciers generate their own stream systems, either on their surface or within and below the ice, in a similar manner to streams in limestone regions. During the peak period of melting in early summer, the stream that emerges at the terminus of a glacier is often a spectacular torrent, frequently flooding the valley floor below. Yet in winter, discharge is reduced to a mere trickle or locked solid. These extremes between summer and winter provide a fascinating range of meltwater features on and around glaciers (Hambrey and Alean, 1994).

The mass of a glacier is constantly changing as the weather varies from season to season and, on longer time scales, as local and global climate change. These ongoing environmental changes cause fluctuations in the amount of snow added to the glacier surface and in the amount of snow and ice lost by melting (Skinner and Porter, 1992). The development of meltwater channels on the surface of a glacier depends on the rate of melting, the rate of deformation of the ice, the extent of crevasses and the pattern of other structures. Surface channel systems develop best on stagnant and on cold glaciers, but will not appear at all on those with a large number of crevasses. Not a great deal is known about the internal drainage systems of glaciers. Nevertheless, through the use of dye tracers it is possible to monitor how fast water travels through them (Hambrey and Alean, 1994).

Coastal Environments

There have been some comprehensive studies of coastal circulation in the Gulf of Alaska as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) of the Bureau of Land Management and the National Oceanic and Atmospheric Administration (Reed et al., 1981). This work allowed a fairly detailed specification of the coastal flow regime in the northeast Gulf of Alaska near Yakutat. Along the northwest Gulf of Alaska (Prince William Sound -Copper River area through the Shelikof Strait), a well-defined westward coastal current is present known as the Kenai Current. In the northeast Gulf of Alaska, however, the sea-level data indicate little evidence of well-developed baroclinic coastal flow (driven by pressure gradient from freshwater drainage) near Sitka and Yakutat, with maximum net flow in winter during the period of maximum winds (Reed et al., 1981).

Portions of two glacial fjords are within WRST's coastal boundary, Icy Bay and Disenchantment Bay. Within them, water exchange may be partially restricted by sills near their entrances, over which the less dense and less saline surface water flows freely outward, but inward flow of the more dense marine water may be restricted. Upward mixing of salt causes surface salinity to increase with distance from the fjord head. Vertical circulation occurs primarily in winter. Nutrients are increased, both from terrestrial runoff and from upwelling of deeper waters (U.S. Department of the Interior, 1974).

Tidewater glaciers are very active along WRST's coast. Rapid advance of the Hubbard Glacier in 2002 closed off Russell Fjord at the head of Disenchantment Bay, causing waters in the fjord to rise 61 feet behind the ice wall before it broke, releasing peak flows of 1.8 million cfs into the bay.

Volcanic Environments

Volcanic activity occurred in three separate eras - Paleozoic, Mesozoic, and Cenozoic - in the Wrangell and part of the St. Elias mountains. Major eruptions have occurred as recently as 1,500 years ago (Lerbekmo and Campbell, 1969).

Most of volcanoes of the western Wrangell mountains are unlike other volcanoes located around the Pacific rim. Rather than erupting explosive lavas forming steep-sided cones, they have been built by the accumulation of hundreds of relatively fluid lava flows to form broad mountains with gentle slopes, typical of shield volcanoes. Now only youthful Mount Wrangell still displays a shield-like form; the other, generally older volcanoes have had much of their superstructure removed by glacial and other erosional processes. On the western flank of Mt. Drum are three large thermal springs known as mud volcanoes (Figure 4): Shrub, Upper Klawasi, and Lower Klawasi (Nichols and Yehle, 1961). These three mud volcanoes of the Klawasi group are evidence for the existence of a warm and possibly a hot water hydrothermal system in the Copper River Valley. These thermal springs are characterized by carbon dioxide gas and warm sodium bicarbonate and sodium chloride waters (Nichols and Yehle, 1961). A field visit in 1999 found the hot springs discharge to be similar, but somewhat more widespread than in the previous two years, with evidence of animal and vegetation deaths from carbon dioxide exposure in the immediate area (Sorey et al., 2000). Maximum fluid temperatures in each of the three main discharge areas, ranging from 48-54°C, were equal to or higher than those measured in the two previous years (Sorey et al., 2000). The origin of the saline water in the Copper River Basin is not known with certainty (Hawkins and Motyka, 1984). Motyka et al. (1989) believe that an igneous intrusion is releasing carbon dioxide and causing metamorphic decarbonation of limestone beds beneath the Klawasi group of mud volcanoes. The high arsenic concentrations suggest that the basal portion of the Chitiston limestone is the source of the metamorphic carbon dioxide (Motyka et al., 1989). The major growth of the Shrub and Upper Klawasi cones ceased prior to the last major glaciation, but intermittent activity has continued on a minor scale to the present. The Lower Klawasi mud volcano, one of the largest cones in the region, was formed principally in post-glacial time (Nichols and Yehle, 1960).The western Wrangells area captured the interest of the state of Alaska and U.S.Geological Survey due to the potential for geothermal energy development (NationalPark Service, 1986). Extreme climatic conditions in Alaska and the lack of transportation infrastructure and viable markets make geothermal energy unprofitable for extraction. The Bureau of Land Management has never issued a geothermal steam leasein Alaska and no sales are scheduled in the foreseeable future (Barr, 2001).

Source National Park Service, Water Resources Division

References

Barr, D.L. 2001. (Draft) The Geothermal Steam Act and the National Park Service. Department of Energy, Yucca Mountain Project. Executive Potential Program Developmental Assignment, August 20, 2001 to October 19, 2001 . p. 13.

Hambrey, M. and J. Alean. 1994. Glaciers. Cambridge University Press. New York , NY . 208 pp.

Lerbekmo. J.F. and F.A. Campbell. 1969. Distribution, Composition, and Source of the White River Ash, Yukon Territory . Canadian Journal of Earth Science 109 (6).

Motyka, R.J., R.J. Poreda, and A.W.A. Jeffery. 1989 Geochemistry, isotopic composition, and organ of fluids emanating from mud volcanoes in the Copper River basin , Alaska . In Geoimica et Cosmochimica Acta. vo153. pp. 29-41.

National Park Service. 1986. General Management Plan, Land Management Plan, Wilderness Suitability Review. Wrangell-St. Elias National Park and Preserve, Alaska . 239 pp.

National Park Service. 1998b National Park Service Procedural Manual 77-1: Wetland Protection, Technical Report NPS/NRWRD/NRTR-98/203. National Park Service, Water Resources Division, Ft. Collins, CO. 32 pp.

Nichols, D.R. and L.A. Yehle. 1961. Analyses of Gas and Water from Two Mineral Springs in the Copper River Basin , Alaska . Geological and Hydrological Sciences. Article 353. D191-D194.

Prowse, T.D. and R.L. Stephenson, R.L. 1986. The Relationship Between Winter Lake Cover, Radiation receipts and the Oxygen Deficit in Temperate Lakes . Atmos.­Ocean 24:386-403.

Prowse, T.D. 1994. Environmental Significance of Ice to Streamflow in Cold Regions. Freshwat. Biol. 32:241-259.

Reed R.K., J.D. Schumacher and C Wright. 1981. On Coastal Flow in the Northeast Gulf of Alaska Near Yakutat. Atmosphere-Ocean 19(1). Canadian Meteorological and Oceanographic Society. pp. 47-53.

Rouse, W.R., M.S.V. Douglas, R.E. Hecky, A.E. Hershey, G.W. Kling, L. Lesack, P. Marsh, M. McDonald, B.J. Nicholson, N.T. Roulet, and J.P. Smol. 1997. Effects of Climate Change on the Freshwaters of Arctic and Subarctic North America . [In] M.G. Anderson, N.E. Peters, D. Walling (eds.), Hydrological Processes. 2:873-902.

Shaine, B.A. 1973. The Wrangell Mountains : Toward an Environmental Plan. Environmental Studies Office, University of California . Santa Cruz , CA .

Skinner, B.J and S.C. Porter. 1992. The Dynamic Earth, an introduction to physical geology. John Wiley & Sons, Inc. New York . pp. 297-325.

Sorey, M.L., C. Werner, R.G. McGimsey, and W.C. Evans. 2000. Hydrothermal activity and carbon-dioxide discharge at Shrub and Upper Klawasi mud volcanoes, Wrangell Mountains , Alaska . U.S. Geological Survey. Water Resources Investigations Report 00-4207. Menlo Park , CA 15 pp.

U.S. Department of the Interior. 1974. Final Environmental Statement. Wrangell-St. Elias National Park , Alaska . Alaska Planning Group. Anchorage , AK . 764 pp.

Warhaftig, D. 1965. Inventory and Cataloging of Sport Fish and Sport Fish Waters of the Copper River, Prince William Sound, and Upper Sistna River Drainages. Annual Report. Alaska Department of Fish and Game, Sport Fish Division.

A Preeminent Mountain Wilderness
Incredible!
You have to see Wrangell-St. Elias National Park and Preserve to believe it-and even then you are not too sure. The number and scale of everything is so enormous.

  • Peaks upon peaks.

  • Glaciers after glaciers.

  • If you follow any of the many braided rivers and streams to their source, you will find either
    • a receding glacier,
    • an advancing glacier, or
    • a tidewater glacier
    .
  • Several mountain ranges converge here, and the park includes 9 of the 16 highest peaks in the United States.

  • The total acreage makes this the largest U.S. national park, the size of six Yellowstones.

  • And beyond all that, it contains a representative sampling of Alaska's wildlife and old mining sites indicative of man's early explorations here.
Hike into these mountains, boat the rivers, ski across the glaciers, fly over the area, and see geology in the making. Amid the splendid isolation comes a feeling of discovery, a feeling that you might be the first person to see such sights. There are so many peaks that you quickly abandon the urge to learn their names and just settle back and appreciate their beauty, their size, their ruggedness. Few roads mean that many travelers will not enter the park itself, but even then some of its major peaks, including Blackburn, Sanford, Drum, and Wrangell, can be seen from nearby highways. Position yourself in one spot and watch the sun, clouds, and storms play "hide and seek" with a single peak or ridge. The mood changes by the minute.

Four major mountain ranges meet here:

  1. The Wrangells huddle in the northern interior;

  2. the Chugach guard the southern coast;

  3. the Saint Elias Mountains rise abruptly from the Gulf of Alaska thrusting northward past the Chugach and on toward the Wrangells;

  4. and the eastern end of the Alaskan Range, mapped as the Nutzatin and Mentasta Mountains, form part of the preserve's northern boundary.
The Wrangells are volcanic in origin, but only Mount Wrangell remains active with vents of steam near its summit. It last erupted in 1930. With adjoining Kluane National Park in Canada, all these ranges form the premier mountain wilderness in North America. The high country is covered with snow the year round, resulting in extensive icefields and glaciers.
  • The Bagley Icefield near the coast is the largest subsolar icefield in North America and spawns such giant glaciers as the Tans, Miles, Hubbard, and Guyot.

  • The Malaspina Glacier flows out of the St. Elias Range between Icy Bay and Yakutat Bay in a mass larger than the State of Rhode Island. It carries so much glacial silt that plants and trees take hold on its extremities, grow to maturity, and topple over the edge as the glacier retreats.

  • Flowing from the glaciers are a multitude of meandering rivers and braided streams. The Copper River, the largest, forms the western boundary of the park starting in the Wrangells and emptying into the Gulf of Alaska in Chugach National Forest.
In the early 1900s the Kennecott Mining Co. transported copper from its mines near McCarthy by railroad along the Chitina and Copper rivers to ships at Cordova. Ore was extracted from these highly productive mines between 1911 and 1938 and lured many people to the area, if only temporarily.

Similarly gold was transported from the Nabesna area. Today mining still occurs on private lands within the park, and you can see evidence of earlier mining, including the ruins of the Kennecott mines, which have been placed on the National Register of Historic Places.

Indian villages expanded and a number of new towns sprang up in mining's heyday. Copper Center, Chitina, Gulkana, and Chistochina are among the old Athapascan settlements. Yakutat, on the coast, is a traditional Tlingit fishing village.

Though the vegetation may seem sparse, especially in the interior, the park contains a variety of wildlife.

  • Dall sheep and mountain goats patrol the craggy peaks.

  • Herds of caribou feed on the lichen and low woody plants around the Wrangells.

  • Moose browse in sloughs and bogs in the coastal lowlands and in brushy areas, which also attract brown/grizzly bears.

  • Black bears roam throughout the park.

  • Bison were released in the Copper and Chitina River valleys in 1950 and 1962 respectively and remain as separate herds today.

  • Many rivers, streams, and lakes provide spawning grounds for salmon and other fish.
    • The Copper River drainage and the Malaspina forelands are major flyways for migratory birds and include prime nesting sites for trumpeter swans.

    • The coastal areas are habitat for marine mammals, including sea lions and harbor seals.

Enough superlatives; explore the park and discover it for yourself!



park maps subheading

The General park map handed out at the visitor center 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.

photo album subheading

A photo album for this park can be found here.

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

Information about the park's research program is available on the park's research webpage.

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.



selected links subheading

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

teacher feature subheading

Currently, we do not have a listing for any park-specific geology education programs or activities.

General information about the park's education and intrepretive programs is available on the park's education webpage.

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/wrst/index.cfm   I  Email: Webmaster
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