This is a close up picture of the Alaska Pipeline. It's 4 ft in diameter. Note the "slide" its setting on so it can move between the two verticle pilings as the ground shifts. The pilings set in the perma frost (that is ground that is always frozen). When the heat of the day transfers to the permafrost via the pilings, it realeases gasses in the pilings that come out through the "vents" you see on top of the pilings. This cools the pipe and thus keeps the perma frost frozen. This pipeline is 800 miles long..amazing.