II.

Physical Geography of Alaska

Alaska occupies the northwestern portion of North America. It includes the Aleutian Islands, a chain of about 150 islands that arcs westward across the Pacific Ocean for 1,800 km (1,100 mi).

Alaska has a total area of 1,717,854 sq km (663,267 sq mi), including 44,659 sq km (17,243 sq mi) of inland water and 70,057 sq km (27,049 sq mi) of coastal water over which the state has jurisdiction. Alaska has a larger area of lakes and rivers than any other state, equaling more than the entire land area of Massachusetts and Vermont combined. The state’s greatest dimensions are about 2,240 km (about 1,390 mi) from north to south and about 3,550 km (about 2,210 mi) from east to west. The mean elevation is about 580 m (1,900 ft). A large area, north of an imaginary line from the Seward Peninsula through Fort Yukon to the Canadian border, lies within the Arctic Circle. Alaska’s Little Diomede Island in the Bering Strait is 4 km (2.5 mi) east of Big Diomede Island, or Ratmanov Island, which belongs to Russia (see Diomede Islands). Fairbanks, in the center of the state, is 5,280 km (3,280 mi) by air from New York City, 5,670 km (3,520 mi) from Tokyo, and 6,810 km (4,230 mi) from London. This key position, at the northern end of the Pacific Ocean and close to Asia, is a major factor in Alaska’s continued economic importance.

A.

Natural Regions

Alaska can be divided into three major natural regions: the Coast Ranges region, the Interior region, and the Arctic region.

The Coast Ranges region is an area of high mountains, great valleys, and many islands. It extends about 1,900 km (about 1,200 mi) along Alaska’s Pacific coast and is generally narrower than about 300 km (about 200 mi). It can be divided, in turn, into the subregions of southeastern Alaska, south central Alaska, and southwestern Alaska.

Southeastern Alaska, often called the Alaska Panhandle, or Panhandle, is a narrow, mountainous strip of the mainland between British Columbia and the Pacific Ocean. It is fringed by the Alexander Archipelago, a group of 1,100 islands. Between the islands and the mainland is part of the Inside Passage, a deep natural waterway used by vessels traveling along the coast. The islands of the archipelago are the tops of submerged mountains, whose peaks rise steeply about 900 to 1,500 m (about 3,000 to 5,000 ft) above the water. On the mainland the Boundary Range rises abruptly from the water’s edge, and varies in elevation from 1,500 to more than 3,000 m (5,000 to more than 10,000 ft).

In the northern section of the Alaska Panhandle and in adjoining areas of Canada are the Saint Elias Mountains, which reach 5,489 m (18,008 ft) above sea level at Mount Saint Elias, one of the highest peaks in North America.

The fjords along the coast are deep, narrow inlets that have been gouged out by glaciers and then partly submerged by the sea. Glaciers in Alaska number more than 100,000. Vast glaciers occur in the mountains northwest of Juneau. At Glacier Bay the huge Muir Glacier towers 60 m (200 ft) above the water. At the foot of Mount Saint Elias is the Malaspina Glacier, which covers an area larger than Rhode Island. The Malaspina Glacier is the largest piedmont glacier in North America. A piedmont glacier occurs at the foot of a mountain range and consists of a large number of valley glaciers that coalesce. Just north of the Saint Elias Mountains are the volcanic Wrangell Mountains, which include Mount Wrangell, Mount Sanford, and Mount Drum.

South central Alaska extends around the Gulf of Alaska from the Malaspina Glacier to the Alaska Peninsula. It is bounded on the north and west by the Alaska Range, a belt of mountains 80 to 100 km (50 to 60 mi) wide that is connected with the Saint Elias Mountains on the east. The Alaska Range includes Mount McKinley, whose south peak is the highest point in North America at 6,194 m (20,320 ft). The coastal section of south central Alaska resembles that of the Panhandle. North of Cook Inlet, broad river flats lead inland to the Susitna and the Matanuska river valleys, which comprise the only extensive lowland area in the Pacific Mountains region.

Southwestern Alaska is composed of the narrow Alaska Peninsula, the Aleutian Islands, and Kodiak Island. The backbone of the peninsula is the volcanic, heavily glaciated Aleutian Range, which continues through the Aleutian Islands to the Kamchatka Peninsula. With more than 50 active volcanoes, the Aleutians are the site of frequent eruptions, including in recent years Mount Veniaminov and Mount Augustine in lower Cook Inlet. From time to time major eruptions shake the area. Novarupta Volcano and Katmai Volcano, at the base of the Alaska Peninsula, erupted in 1912 and created the Valley of Ten Thousand Smokes. The Aleutian Islands, or Aleutians, are an extension of the Aleutian Range and divide the Bering Sea from the Pacific Ocean. Cape Wrangell, in the Aleutians, is the westernmost point in the United States. Kodiak Island is the second largest island in the United States. The Pribilof Islands, also part of Alaska, lie in the Bering Sea northeast of the Aleutian Islands.

The Alaskan Interior is bounded by the Alaska Range on the south, the Brooks Range on the north, the border with the Yukon Territory on the east, and the Bering Sea on the west. It contains the Tanana Yukon Upland, with maximum elevations in the east of about 1,200 m (about 4,000 ft) and separating the lowlands or flats of the Yukon and Tanana rivers, and ends at the vast lowland between the lower Yukon and Kuskokwim rivers. The Yukon Flats, northeast of Fairbanks, form a large depression surrounded by highlands and have the coldest winter and hottest summer temperatures in Alaska. Once the Kuskokwim River passes through the Kuskokwim Mountains, it forms the southern edge of a vast lake-studded alluvial plain bounded on the north by the Yukon River. This water-logged lowland is a major summer nesting area for birds. Fairbanks is the major city in this region, while Fort Yukon is the major community in the Yukon Flats and Bethel the largest settlement on the Lower Kuskokwim River.

The glaciated Brooks Range separates Interior from Arctic Alaska. Its highest elevations are in the east near the border with the Yukon Territory, and it extends almost to the Chukchi Sea in the west. The western Brooks Range consist of two ranges, the Baird and DeLong Mountains, and is drained by the Noatak River. The Dalton Highway, connecting Fairbanks with Prudhoe Bay on the Arctic Ocean, crosses the Brooks Range at Atigun Pass.

The Arctic Region is bounded by the Beaufort Sea to the north, the Chukchi Sea to the west, and the crest of the Brooks Range to the south. It is crossed by numerous northward-flowing rivers, the largest of which is the Colville. The region has never been subject to glaciation; contains continuous permafrost; enormous deposits of coal, petroleum, and natural gas; and is the summer calving grounds for hundreds of thousands of caribou and nesting grounds for migratory birds. It consists of the northern slopes and low foothills of the Brooks Range and a large Arctic coastal plain, popularly called the Arctic Slope or simply the Slope (see North Slope). The eastern portion of the plain is narrow, extending only 19 km (12 mi) from the mountains to the sea at Demarcation Point, marking the boundary with the Yukon Territory, but reaches a width nearly ten times as great at Point Barrow, the northernmost point in the United States. The region’s principal settlement, Barrow, is near the point. The region contains at Prudhoe Bay the largest oilfield in the United States. The area east of the Colville River is encompassed by the Arctic National Wildlife Refuge (ANWR), the area to the west by the National Petroleum Reserve-Alaska. Small deposits of petroleum and natural gas, as well as huge deposits of coal, are known to be in the National Petroleum Reserve, but the largest petroleum deposits are believed to exist in the Arctic National Wildlife Refuge.

B.

Rivers and Lakes

The principal river is the Yukon River, which rises in the nearby Yukon Territory. About two-thirds of its 3,190 km (1,980 mi) course lies in Alaska. The Yukon is one of the longest navigable rivers in the world, and it flows westward in a gently curving arc across the Interior region to the Bering Sea just south of Norton Sound. Shallow-draft riverboats and barges can navigate its whole length during the ice-free summer weeks. Its main tributaries include the Porcupine, the Tanana, the Koyukuk, and the Innoko rivers. The silt laden, glacially fed Yukon forms a large delta with numerous shallow channels, or distributaries.

The second great river of Alaska is the Kuskokwim, 1,165 km (724 mi) long. Its four headstreams rise in the Alaska Range. The river winds southwestward to the Bering Sea. Near the end of its course the river approaches the Yukon, and shallow channels link the two river systems.

The Colville River flows into the Beaufort Sea; the Noatak, Kobuk, and Selawik rivers reach the sea near Kotzebue. The main route connecting Anchorage to Fairbanks, over Broad Pass, follows the Susitna and Chulitna rivers. The Copper River forms a huge delta, and provides access to the Interior from Glenallen. Cordova was at one time the port for the Copper and Chitina rivers. Wrangell remains the port for the Stikine River. The Alsek River is unusual in that it does not form an easily visible mouth or delta.

Alaska’s largest lake is Iliamna Lake at the foot of the Alaska Peninsula, covering 2,647 sq km (1,022 sq mi).

C.

Coastline

Measured roughly along its perimeter, Alaska’s coastline is 10,690 km (6,640 mi) long. However, if all the inlets and islands are taken into account, the total length is 54,563 km (33,904 mi). Along the Pacific coast, the shoreline is deeply indented. The Inside Passage, sheltered from the open ocean, is a calm body of water, but it is difficult to navigate in foggy weather. The coast of the Gulf of Alaska has tides that reach as high as 6 m (20 ft). It is buffeted by major storms, and occasionally by tsunamis caused by earthquakes under the ocean. At Cook Inlet high tide and low tide sometimes differ as much as 9 m (30 ft).

The current through the Gulf of Alaska is known as the Alaska Current. It flows westward and then, in the eastern Aleutians, turns northward to bring warm water along the western coast of Alaska all the way to Point Barrow. The coastline of the Bering Sea, except for part of the southern Seward Peninsula, is mostly shallow, with offshore bars and lagoons. Most of the coast of the Chukchi and Beaufort seas is similar. The Bering Sea contains ice during the winter, and the marginal region of the ice is one of the world’s major fisheries. In summer the ice slowly retreats northward into the Arctic Ocean, allowing navigation along the Arctic Coast by late summer.

D.

Climate

Alaska has four different climatic zones: maritime, continental, transitional, and Arctic. Kodiak, the Aleutians, and southeastern and south central Alaska have a climate primarily influenced by the sea, so that temperatures do not vary greatly throughout the year, but rainfall is quite heavy and frequent. Western Alaska, a transitional climate, has much lower temperatures and less rainfall, but, like the Aleutians, frequent periods of extremely high winds and blowing snow. Arctic Alaska has very little snowfall, cool summer temperatures, and frequent high winds, particularly from the east. The interior has a continental climate characterized by extremely great temperature variations, but only moderate rain and snow.

The average January temperatures in southeastern Alaska are close to freezing, but snowfall in many areas can be high. Rainfall, particularly along the coasts, can exceed 2,500 mm (100 in) a year. South central Alaska has a maritime climate, ranging northward into a transitional climate. The climates of Homer and Kodiak are more similar to southeastern Alaska’s climate than to that of Anchorage. Because of the oceans and the mountains, and the storms coming from the Gulf of Alaska, this region shows considerable variation from place to place in rainfall and snowfall. For example, Thompson Pass, north of Valdez, has recorded more than 6 m (20 ft) of snowfall in one winter, whereas Anchorage often has little snow all winter long. Under proper conditions, however, cold air from the interior can cross the mountains and bring temperatures in the upper -20°s C (lower -20°s F) to this region.

The Aleutians, dominated by perpetual low pressure systems and contrasting ocean currents, have frequent fogs, high winds or “williwaws,” and rainstorms, making the region extremely difficult for both vessel and aircraft transportation. The interior has a continental (also called sub-Arctic or taiga) climate caused by being in the rain shadow of the coast ranges and inland. Winter cold spells can last several weeks, with temperatures recorded in the -50°s C (-60°s F), while summer temperatures, particularly in the Yukon Flats, can reach into the upper 30°s C (upper 90°s F). Summers are characterized by frequent thunderstorms, which often cause forest fires. Mean annual precipitation is about 380 to 510 mm (about 15 to 20 in), with winter snowfalls varying significantly from year to year but averaging in lowland areas at about 1,300 mm (about 50 in).

Western Alaska, from the Alaska Peninsula northward to the southern Seward Peninsula, has a transitional climate, one influenced by frequent low pressure systems from the Bering Sea, but also by cold air from the interior and winter sea ice conditions. The result is summer temperatures that seldom rise much above 10°C (50°F), and winter conditions characterized by high winds and snow storms. Arctic Alaska, stretching from the northern Seward Peninsula (Kotzebue Sound) northward to Barrow and eastward to Demarcation Point, has an Arctic climate characterized by low winter and summer temperatures and frequent high winds. While snowfall is low, generally less than 300 mm (12 in), blowing snow frequently creates a condition known as whiteout, in which people cannot differentiate between land and sky, making it extremely easy to become disoriented and lost. Summers are cool, with temperatures generally less than 10°C (50°F) and rainfall tends to concentrate in late summer. The high winds along the coast of the Beaufort Sea blow away insects and make the area favorable to caribou in the summer months.

Because of Alaska’s high northern latitude, the length of day varies much more between summer and winter than it does in other parts of the United States. At Fort Yukon, on the Arctic Circle, the sun barely rises above the southern horizon on the shortest day of the year, December 21. At Barrow, on the Arctic Coast, the sun is not seen from late November until late January. In summer the days are much longer and Alaska is as much “the land of the midnight sun” as are Norway and Sweden. At Barrow there is continuous daylight from early May to early August.

E.

Soils

Most Alaska soils are immature, cold, and acidic. Except for the lowlands of southeastern and south central Alaska, and portions of the lowlands in the Interior, most Alaska soils are permanently frozen, a condition called permafrost. At a certain depth in the ground, the soil remains perpetually frozen. This level is known as the permafrost table and the ground beneath is known as the inactive layer because it never thaws. The soil above, however, freezes and thaws every year, and in the process the soil is constantly churned. The permafrost table is impervious to water. Therefore the surface in much of the Interior, western, and Arctic Alaska is waterlogged and contains numerous but usually shallow lakes often called thaw lakes, in spite of the region’s low precipitation. Thaw lakes form when large blocks of ground ice contained in the inactive layer thaw and leave a hole in the surface, which fills with water. On the Arctic coastal plain these lakes are generally rectangular in shape, whereas in the Interior and western Alaska they are usually oval in form. Such lakes fill in with vegetation over time, and in the Interior eventually with trees. Thus the lakes are not permanent, but are constantly changing, with new lakes forming and others being filled in with vegetation. About 80 percent of Alaska contains permanently frozen ground. Of this, over half is called continuous permafrost, that is, has an active layer of only a few inches to a foot or so in depth. The remainder is called discontinuous permafrost, where the active layer may be many feet in depth.

F.

Plant Life

Forests cover about a third of Alaska’s land area. The most important commercial species of trees are birch, Sitka spruce (the state tree), western hemlock, black spruce, and white spruce.

The Alaska Panhandle is a land of forests. The mild climate and heavy rainfall promote dense tree growth. The huge Tongass National Forest is an area where young saplings compete for space with trees that are centuries old. Trees found there include the western hemlock, Sitka spruce, canoe cedar, and yellow cedar (also called Alaska cedar), which are all conifers. The forest floor is carpeted with berry-producing plants and moss.

South central Alaska south of the Alaska Range is also heavily forested, but the trees are usually smaller and there is a transition from Sitka spruce to white and black spruce. The largest stand of timber is in the Chugach National Forest.

Southwestern Alaska is almost entirely treeless, except for Sitka spruce and some cottonwood on Kodiak Island and a few stunted birches and willows found in the Aleutian Islands. However, grasses grow luxuriantly in the cool wet climate. Flowers bloom in great variety and include the forget-me-not (the state flower), anemone, lupine, paintbrush, and marsh marigold in boggy areas, and the dwarf rhododendron on the hillsides.

In the Interior region, vegetation must adapt itself to short, warm summers and long, cold winters. Trees grow slowly, and their root systems must be shallow because they cannot penetrate the permafrost. Toward the west the trees become sparse and are replaced by wet tundra. Similarly, the mountain slopes contain tundra in the Interior. Cleared areas are often brilliant with fireweed in the summer months. Principal trees found in this region are black and white spruce, paper birch, tamarack, aspen, Alaskan larch, and balsam poplar. There are expanses of bogs called muskeg, and grasslands, where many species of wild flowers, berries, and shrubs occur.

Arctic Alaska contains primarily tundra vegetation with tall brush and some forests in stream valleys. Tundra consists of mosses, lichens, and grasses 3 to 5 cm (1 to 2 in) high, sedges and heather up to 20 cm (8 in) high, and willows taller than an average adult person. Tundra is characteristic of the northlands around the Arctic Ocean and of other areas in Alaska above the timberline. Colorful flowers carpet the tundra during the brief summer weeks when the sun never sets, and plants grow well although the soil thaws less than 30 cm (1 ft) before the long winter returns. Here and there, dwarf willows are found.

G.

Animal Life

In southeastern Alaska are found the black bear, grizzly bear, black-tailed deer, moose, mountain goat, marten, red fox, mink, wolf, coyote, otter, and beaver. The sea lion, harbor seal, sea otter, porpoise, and several species of whale are common along the coast. Halibut, herring, cod, crab, and shrimp are also found in abundance in coastal waters. Several species of anadromous (living in both salt and freshwater) fish occur in Alaska, including chinook, coho, sockeye, chum, and pink salmon, Dolly Varden, sheefish, and rainbow and cutthroat trout. Brook and lake trout, Arctic grayling, northern pike, whitefish, and burbot occur in the state’s lakes and streams. Wildlife in south-central Alaska is similar to that of the Panhandle, with the addition of Dall sheep and caribou. In southwestern Alaska is rugged Kodiak Island, the home of the Kodiak brown bear, which is believed to be the largest omnivorous land animal in the world.

The Dall sheep, grizzly bear, moose, wolf, and caribou are found in Denali National Park and Preserve. Gulls, kittiwakes, cormorants, murres, puffins, and other seabirds are found throughout the Aleutian Islands. On the Pribilof Islands are extensive fur seal rookeries and also small colonies of sea otter.

The Interior region is the home of caribou, moose, Dall sheep, mountain goat, bison, wolf, black bear, grizzly bear, and many fur-bearing animals. Thousands of migratory waterfowl arrive at the end of April at their nesting grounds along the lower Yukon and Kuskokwim river valleys and leave in August and September for warmer lands farther south. The Bristol Bay area of the Bering Sea coast is noted for its salmon.

In the Arctic region the sea ice is the habitat of the polar bear, hair seal, and walrus. Marine life is abundant and ranges from tiny crustaceans to giant whales. Caribou graze on the tundra, migrating in herds and returning for the winter to range south of the Brook Range. The Arctic is a major nesting area for waterfowl, shorebirds, and many raptors, including peregrine falcons.

H.

Conservation

Alaska is experiencing environmental changes that scientists attribute to global warming. These changes include rising average temperatures, retreating glaciers, melting sea ice, coastal erosion, thawing permafrost, and alterations in wildlife migration patterns. Although the state has taken an inventory of its greenhouse gas production, it has yet to take steps to limit production of these gases, which are believed to play a major role in global warming.

Alaska’s Department of Environmental Conservation is responsible for the conservation, protection, and improvement of the state’s natural resources and environment and for the control of water, land, and air pollution.

H.1.

Air Quality

While air quality in Alaska is generally good, the state has a few air pollution problems. A leading problem is high levels of carbon monoxide in urban areas during winter. During temperature inversions in winter, which trap pollutants near the ground, air quality in Fairbanks and Anchorage occasionally fails to meet federal standards. Automobiles, and in Fairbanks coal-fired power plants and home heating, contribute to air pollution. Toxic air emissions, especially ammonia and benzene, are largely confined to areas near oil refineries.

H.2.

Waste Management

Landfills designed with modern environmental safeguards have been opened in Alaska, although much of the state’s solid waste is disposed of in older facilities. Open dumps are the primary disposal facilities in rural Alaska. The state made progress in reducing the amount of toxic chemicals discharged into the environment during the late 1990s and the 2000s.

H.3.

Water Quality

Virtually all of the state’s waters are unpolluted. Nevertheless, many in Alaska drink water from systems that violate federal safe drinking water standards. Most of the drinking water problems stem from inadequate public sewerage, especially in rural areas. Water quality has also suffered because of oil spills and poor petroleum waste disposal practices. In March 1989 the supertanker Exxon Valdez ran aground in Prince William Sound and discharged about 260,000 barrels, one of the worst oil spills in U.S. history. Experts estimated that the environmental and ecological damage caused by the spill could take decades to undo.