So how these thaw lakes are formed has to do with...OK, it starts with ice wedges.The top part of the ice
wedge melts. Should I back up?
Ice wedges form when water runs into cracks in the ground, the permafrost, then freezes.You ever see mud
after it dries? Dried mud has cracks because when it dries it contracts, it shrinks.
Well, in winter permafrost behaves similarly.It shrinks in winter because it freezes even more thoroughly then.
And as it shrinks, it forms deep, deep cracks.Then in the summer, when the active layer, the top layer of the
permafrost, melts, the melt water runs into those cracks in the permafrost, then freezes again, because that
ground, the ground beneath the active layer is still below freezing. So you have wedges of ice in the
permafrost.
Now, the ice wedges widen the original cracks in the permafrost because water expands when it freezes. All
right, OK.Then in the autumn, the active layer on top freezes again.Then in winter the permafrost starts
contracting again and the cracks open up even wider.So the next summer when the active layer melts again
and flows into the widened cracks and freezes, it makes the cracks even wider. So it's sort of a cycle through
which the cracks and the wedges grow wider and wider. So when the ice wedge reaches a certain size, its top part in the active layer turns into a little pond when it melts in the summer. And that's the beginning of your
thaw lake.
이게 듣기 지문이고요... Alaska에 Thaw lake라는 것이 어떻게 형성되는지에 대한 설명이에요.
이 문제 TPO에 나오는 문젠데 정답률이 20%라네요. 제가 이 문제를 거의 6번을 도전했는데 한 번도
맞힌 적이 없네요ㅠ 진짜 역대급으로 어려운 것 같은.. 이제껏 푼 토플 문제 중에서 가장 어려운 것 같네요ㅠ
문제의 문제는 이거에요ㅠ
2. The professor explains thaw lake formation as a cycle of events that occur repeatedly.
Summarize this cycle.
A. Melt water flows into cracks in permafrost
B. Ice wedges inside permafrost completely melt
C. Freezing water expands cracks in permafrost
D. Ice in the active layer melts as temperatures rise
E. Permafrost shrinks and cracks as temperatures drop.
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답은 EDACB 라는데 아예 감이 안 오네요ㅠ
그리고 이 문제 특히나 더 헷갈리는 포인트는 이게 기본적으로 싸이클에 대해 언급하는 건데
어디를 첫머리로 잡아야 할지 모르겠다는 점이에요. 왜 꼭 반드시 E가 맨 앞에 와야 하는지
납득이 안 가고요. 듣기 지문에서는 water가 crack으로 run into 한다는 얘기가 맨 먼저 설명되는
것 같아서 저는 A를 맨 앞에 두었거든요...