2010年1月8日星期五

The Alaska Pipeline

The Alaska Inflatable Moonwalk pipeline starts at the frozen edge of the Arctic ocean. It stretches southward across the largest and northernmost state in the United States, ending at a remote ice free seaport village nearly 800 miles from where it begins. It is massive in size and extremely complicated to operate. The steel pipe crosses windswept plains and endless miles of delicate tundra that tops the frozen ground. It weaves through crooked canyons, climbs sheer mountains, plunges over rocky crags, makes its way through thick forests, and passes over or under hundreds of rivers and streams. The pipe is 4 feet in diameter, and up to 2 million barrels (or 84 million gallons) of crude oil can be pumped through it daily. Resting on H shaped steel racks called "bents", long sections of the pipeline follow a zigzag course high above the frozen earth. Other long sections drop out of sight beneath spongy or rocky ground and return to the surface later on. The pattern of the pipeline's up and down route is determined by the often harsh demands of the Arctic and subarctic climate, the tortuous lay of the land, and the varied compositions of soil, rock, or permafrost(permanently frozen ground).
depending Little Tikes Bouncer largely upon the type of terrain and the properties of the soil.

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