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. "USA" © Emmanuel BUCHOT, Encarta, Wikipedia
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