earthquakes is that: , A., The rare, deepest ones are caused by “implosion” as minerals in downgoing slabs of subduction zones suddenly switch to a denser arrangement, whereas common shallower ones are caused by elastic rebound of bent rocks when a fault breaks. B., The deepest ones are caused by elastic rebound of bent rocks when a fault breaks, whereas shallower ones are almost all caused by collapse of natural caves such as Mammoth Cave. C., They are caused by Pepsi machines exploding after being kicked by Coke drinkers.
D., Human-made atomic-bomb testing is responsible. E., They are caused by Coke drinkers kicking the Pepsi machines in Penn State buildings. “Implosion” is the currently favored idea. As subduction zones take rocks deeper where pressure is higher, the building blocks tend to reorganize to take up less space, shifting from, say, a one- on-top-of-another pattern to a fit-in-the-space-between-those-below pattern. Sometimes, this seems to be delayed and then to happen all at once (I can’t move until my neighbor does…), giving an implosion. The biggest, deepest earthquakes happen where temperatures and pressures are so high that we don’t think rocks can break. Humans have never made a hole anywhere nearly as deep as the deeper earthquakes. We have mostly quit testing atomic bombs. And, a big earthquake is way bigger than a big atomic bomb. Penn State students, being naturally even- tempered, don’t kick hard enough to actually explode Pepsi machines. And Penn State basements are not deep enough to account for the deeper earthquakes. , Points Earned:, 1/1 Correct Answer:, A Your Response:, A 13. , Volcanic eruptions cause many hazards to humans, and many geologists are employed to study these hazards and warn people. For a single, large, explosive volcanic eruption such as Mt. St. Helens, which of the following is not a worry that these volcanic-hazards geologists would warn people about? , A., Tsunamis, or giant waves, that could drown people, if the volcano is in the ocean or a very large lake and the eruption moves a lot of water out of the way. B., Pyroclastics, including bus-sized pieces that could fall on people’s heads and kill them. C., Poisonous gases, that could kill people who breathe them in. D., Mudflows and landslides that could bury people and buildings. E., Climatic warming, with the volcano causing a sudden heat wave that would harm people living in big cities. This is one of those interesting cases where “slow” and “fast” are different. Volcanoes release carbon dioxide, and carbon dioxide warms. But carbon dioxide stays up a long time, and no single volcanic eruption puts up enough carbon dioxide to make a detectable difference to the concentration in the air and the temperature of the Earth. However, a single big eruption can put enough material into the stratosphere to block enough sunlight to cool the Earth by a degree or two for a year or two. So the climatic hazard from a single big volcanic eruption is cooling, not warming. Explosive volcanoes are often large and steep, and may have huge glaciers. As heat
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- Fall '08
- Earthquakes, Correct Answer, Volcano, St. Helens, Points Earned