5. Heat is moved around by convection, conduction and radiation (and by lemmings carrying space heaters, if lemmings ever carry space heaters). Which statement is more nearly correct? A) No matter where you are, lemmings carrying space heaters are always moving more heat than convection is moving. B) Convection moves heat efficiently through the soft, hot rocks of the Earth’s mantle, but is not efficient at moving heat through the space between the Sun and the Earth. C) No matter where you are, convection always moves heat more efficiently than does radiation. D) Convection moves heat efficiently through the space between the Sun and the Earth, but not through the soft, hot rocks of the mantle. E) No matter where you are, convection always moves heat more efficiently than does conduction. Points Earned: 1.0/1.0 Correct Answer(s): C Points Earned: 1.0/1.0 Correct Answer(s): E Points Earned: 1.0/1.0 Correct Answer(s): E
Feedback: Heat from deep in the Earth is moved up through the soft bulk of the planet primarily by convection, but convection of rocks certainly does not continue beyond the planet, where radiation becomes dominant. In the shallowest, uppermost layers of the Earth, most of the heat transfer is by conduction. And the poor lemmings deserve a rest and a snack. 6. Volcanoes in Death Valley: valley. Feedback: Death Valley, and many of the surrounding parts of Nevada and California, have experienced geologically recent volcanic activity. This is one of the problems facing the plan to put nuclear waste in an underground repository in Nevada and leave that waste—are we sure that a volcano won’t erupt through the repository? There has not been enough lava erupted to fill the valley, however, nor do volcanoes erupt Diet Pepsi (although you can make a nice volcano model by quickly popping the top of a hot, shaken can of pop). 7. Dust and shells and fish poop and all sorts of things fall to the sea bed to make sediment. Across broad central regions of the ocean, the sediment accumulates at a uniform rate—piling up about as rapidly here as it does over there. And, in most places, the currents don’t move the sediment around much, so that it stays where it falls. Thus, the thickness of the sediment is related to the age of the rocks beneath the sediment. If you go around an ocean and measure the thickness of the sediment in lots of places, you are likely to find:
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- Fall '08
- Correct Answer, Volcano, Death Valley