这是学校的地质学作业 有四题实在不知道该怎麽回答 所以请各位大大帮个忙 谢谢!! ꌊ1.According to plate tectonic theory where are crustal rocks created ? Why doesn`t earth keep getting larger if rock is continually created? 2.In part of major mountain belts there are sequences of rocks that geologists interpret as slices of ancient lithosphere. Assuming that such a sequence formed at a divergent boundary and was moved toward a convergent boundary by plate motion,what rock types would you expect to make up this sequence , going from the top downward? 3.What might explain the remarkable alignment of Cascade volcanoes? 4.A cross-bedded quartz sandstone may have been deposited as a beach sand or as a dune sand. What features could you look for within the rock to tell if it had been deposited on a beach? On a dune? --

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