The Physical Environment
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Earth Biomes

 

tilted polesFigure 13.27 Tilted poles on Northway access road, Yukon region Alaska.
(Courtesy: USGS Digital Data Series CD-ROM DDS-21)

Permafrost is a common feature of the arctic tundra climate and biome. Permafrost refers to permanently frozen ground. Actually, the ground has two layers which freeze. A surface layer, called the active layer, thaws during the short "summer" and often subsides. Beneath the active layer is the inactive layer which stays frozen throughout the year. Permafrost creates a barrier to the rootdevelopment. Larger trees can grow along better drained river valleys where the depth to permafrost is greater. The annual freezing and thawing disrupts root systems inhibiting the growth of very tall vegetation.Alaskan pipeline

Figure 13.28 Trans-Alaska pipeline snakes across the Alaskan tundra
Courtesy: United States Bureau of Land Management

Permafrost creates an engineering nightmare for the construction of buildings and other structures. You can see in Figure 13.26 how telephone poles have been tilted from the heaving of the surface during freezing and thawing. Much concern for damage to the environment was raised over the construction of the Trans-Alaska Pipeline. The heated oil running though the pipeline is insulated from the cold permafrost where it runs underground. In places it zigzags over the surface on stilts that allow it to expand and contract.

 

musk oxFigure 13.29 Musk Ox of the Alaskan arctic tundra. (Courtesy:  U.S. Fish and Wildlife Service)

The Musk Oxen is a well-known inhabitant of the arctic tundra. A dense fur coat protects them from the severe climatic conditions in the tundra. Beneath is a dense fine undercoat that is fairly waterproof. Adults gather in a protective wall to keep the calves safe from predator attacks and severe storms. Musk oxen inhabited much of Eurasia and North America during the Ice Ages, but now survive only in parts of Greenland and northern Canada.

 

 

Video: Arctic National Wildlife Refuge
Courtesy USFWS


 

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For Citation: Ritter, Michael E. The Physical Environment: an Introduction to Physical Geography.
2006. Date visited.  ../title_page.html


Michael Ritter (tpeauthor@mac.com)

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