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stranger
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stranger
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I don't understand the difference between "drumlin" and "moraine".
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Joined: Jun 2008
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Carpal Tunnel
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Carpal Tunnel
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Hold tight: you'll get an answer.
WELCOME
----please, draw me a sheep----
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addict
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addict
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A drumlin is a teardrop-shaped hill that resulted from a glacier moving over loose ("unconsolidated") soil. It forms from soil under the glacier. The point of the teardrop indicates the direction in which the glacier was moving. You can see a similar thing happen when water moves over uneven sand at the beach (Not ripples in the sand, which are formed at right angles to the water's movement.)
A moraine is rubble that is pushed ahead of the glacier (technically, a terminal moraine) and left there marking the forward edge of the glacier when the glacier retreats. Other, non-terminal moraines are also seen, particlarly when the rubble scoured by the glacier from mountain walls as the glacier moves through a valley is concentrated at or near the longitudinal midline of the glacier and left behind like a track of the glacier as the glacier melts.
"I don't know which is worse: ignorance or apathy. And, frankly, I don't care." - Anonymous
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Joined: Mar 2000
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Carpal Tunnel
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Carpal Tunnel
Joined: Mar 2000
Posts: 11,613 |
Moraine:  Drumlin: 
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Sooo... I could have used 2,000 words?
"I don't know which is worse: ignorance or apathy. And, frankly, I don't care." - Anonymous
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Joined: Mar 2000
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Carpal Tunnel
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Carpal Tunnel
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I just thought alely might be a visual learner like I am.
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Joined: Dec 2000
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Carpal Tunnel
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Carpal Tunnel
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I suspect that the main difference is that a moraine is laid down by the glacier from things that it brought along with it, whereas a drumlin is carved out of stuff that's already there.
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Correct. Moraines are transported debris, whereas drumlins are deformed substrate. There is a third term for material that becomes incorporated in the glacier itself as the glacier forms and is left behind in a random pattern as the glacier melts. I don't recall the term. These are typically isolated boulders, but may include animal bones, etc.
@Jackie: I was being self deprecating. I tend to blab.
"I don't know which is worse: ignorance or apathy. And, frankly, I don't care." - Anonymous
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Joined: Mar 2000
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Carpal Tunnel
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Carpal Tunnel
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I tend to blab. Au contraire, Pierre -- that your explanations were so good is why I posted none with the pics. Kind of complementary. 
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Joined: Sep 2010
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stranger
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stranger
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Material incorporated into the glacier is entrained debris. When it is left behind, the general term is "till" (which also applies to moraines). Material that is transported by glacial meltwater is "outwash." Geology has a poetic and interesting terminology. One of my favorite reads is John McPhee's book series "Annals of the Former World," which celebrates the language of geology, as well as the science.
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