# rockon7 - 1 Early scientists studying a glacier put stones...

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1. Early scientists studying a glacier put stones on the ice surface in a straight line across the valley, and came back later to find that the line was bent and moved downhill. The scientists determined that the stones did not slide off the glacier, but were carried by the flow of the glacier. What did the scientists mean by “flow of the glacier”? A) The weight of the stones had broken the ice into chunks that rolled downhill, like dry sand falling off an anthill. B) The sun’s energy had heated the rocks and caused the whole glacier to melt and flow downhill, and then the water refroze at night with the rocks still on top. C) Because the ice was almost warm enough to melt, the ice deformed slowly something like hot iron in a blacksmith shop or a chocolate bar in your pocket. D) The pressure of the stones had converted the ice to a denser, high-pressure phase, and the resulting implosion earthquake had moved the stones. E) The ice had relaxed, taken the day off, and gone out for pizza with its friends, dropping the stones on the way. Feedback: Materials warmed almost but not quite to their melting point can deform without breaking or melting. We saw this with the great convection cells in the mantle, back in unit 2, and we meet it again with ice. If you list the temperature of the ice in degrees F, it is a lot colder than the mantle, or iron heated by a blacksmith, or a chocolate bar in your pocket. But, the ice has been warmed from absolute zero almost to the melting temperature, just like the mantle and the iron and the chocolate, so the stress from gravity can cause the ice to deform or flow. Table for Individual Question Feedback Points Earned: 1.0/1.0 Correct Answer(s): C 2. A glacier almost always flows: A) From south to north. B) From where bedrock is high to where bedrock is low. C) From north to south. D) From where the glacier’s upper surface is high to where the glacier’s upper surface is low. E) Up a mountain. Feedback: The great ice sheet of Greenland spreads from its central dome, so the ice on the

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south side is moving south, the ice on the north side is moving north, the east-side ice moves east and the west-side ice moves west. Ice flows down many mountains, such as Mount Rainier, but ice came across the Great Lakes and up into the US. Thus, ice flows from where its upper surface is high to where its upper surface is low. Table for Individual Question Feedback Points Earned: 1.0/1.0 Correct Answer(s): D 3. In affecting the landscape: A) Glaciers that are frozen to their beds don’t do much, but glaciers that are thawed at their beds and have a lot of meltwater change things rapidly. B) Glaciers that are frozen to their beds change things rapidly, but glaciers that are thawed at their beds and have a lot of meltwater don’t do much.
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• Spring '99
• Furman
• GEOSC010, RockOn7, Correct Answer, Great Lakes, Individual Question, Glaciology, Greenland, moraines

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