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Threatening the village are sinkholes that have formed beside theriver, sending landslides of silt, rock and gravel tumbling intospawning areas for sheefish -- an animal that plays a key role insubsistence diets in the region. The sinkholes are thermokarsts formed when ice beneath the tundravanishes. They produce scooped-out swaths of earth, making them aparticularly visible effect of climate change. Legions of them haveformed in the last decade, but the biggest one in North Americaemerged eight years ago about 175 miles upstream of the village. Selawik Slump The Selawik Slump, as it's called, is a massive pit in the groundpossibly caused by the melting of "old, buried glacier ice,"according to the Selawik National Wildlife Refuge . Up to 8 stories deep, its already grown to 9 square acres. "It looks like a big asteroid hit the earth and made a crater,"said James Beylund, Selawik's acting city administrator. It's expected to keep growing, for years. The crater's steepheadwall is steadily "marching" away from the river as chunks ofice and rock crash to the ground, said Lee Anne Ayres, manager ofthe Selawik National Wildlife Refuge. "It's dramatic," she said. "There's constant running of water,rocks breaking off that headwall, chunks of ice falling down." The headwall moves away from the river several feet each summer. Itcould expand for years: experts say it may until it reaches a ridgeabout a quarter-mile away. All that sediment ends up in the river or near it, Ayres said. Bymid-2011, the Slump had spilled 500,000 cubic meters of sedimentand ice. That's about 50,000 dump truck loads. Refuge scientists are working with others experts, including withthe Alaska Department of Fish and Game, to learn if all thatsediment has hurt sheefish reproduction. About 50,000 sheefishspawn in the river and winter in Kotzebue Sound, near the hub city.The Selawik River is one of only two spawning rivers for theregion's sheefish, among the largest in the world and reaching up to 60 pounds . "It's a pretty important fishery resource," said Ayres. Researchers expect to see the first glimpse of the Slump'sconsequences this summer, when sheefish return to spawn. "The first cohorts of fish are just starting to come back into thepopulation, so this next year will really be revealing as towhether all the fish survive," she said. The e-commerce company in China offers quality products such as China Roll Forming Equipment , China Cable Tray Roll Forming Machine, and more. For more , please visit Purlin Forming Machine today!
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