D., The fault formed when the recent push-together activity that made Death Valley also affected Utah. E., The fault formed when a narrow crack in the Earth filled with lava that then froze. The spreading that opened Death Valley affected a lot of the west, all the way over to Bryce Canyon in Utah. The Sevier Fault, just west of Bryce, formed as pull-apart action broke the rocks, allowing younger rocks including the black lava flow to drop down next to older rocks including the red lake sediments. There really are cases where lava hardens in cracks, or where lava flows fill valleys, but a careful examination of the rocks here shows that the lake sediments have not been heated by really nearby lava, so these lake sediments and the lava must have been placed together after the lava cooled. Push-together faulting, and landslides, do occur, but not here. , Points Earned:, 0/1 Your Response:, B 2., Death Valley is getting wider: , A., True B., False Using techniques such as GPS (Global Positioning System), scientists have measured the distance between the two sides of the valley, and across the Great Basin from western Utah to eastern California including Death Valley. They
found that each year the Great Basin, including Death Valley, is widening an inch or so, roughly as fast as your fingernails grow. , Points Earned:, 1/1 Your Response:, A 3., , The picture at left shows river gravels in the bottom of Death Valley. Based on the lesson materials for this unit, a likely explanation for this occurrence of river gravels in the valley bottom is: , A., The valley was dropped relative to the mountains by faulting; these gravels had been deposited on mountain tops by rivers before the faulting started, and then the gravels were dropped down by the faulting. B., The valley was raised by faulting, bringing up gravels from subterranean caves.C., The valley was paved with gravels by a movie company for a really spectacular stunt in the Dukes of Hazzard movie, involving long-distance car chases and Daisy leaping the boys’ car across the entire park.D., The valley is deep because it was carved by a river, which later dried up when the desert formed, leaving the gravels behind.E., The valley was dropped relative to the mountains by faulting, and rivers now are carrying gravels down from the mountains into the valley. Faulting dropped the valley (or raised the mountains, or more likely both), and the melting snows of the mountains feed rivers that carry rocks down into the valley, slowly filling it up while lowering the mountains. There really are deep canyons that were carved by rivers, but as we saw in class and online, Death Valley is not one of them. Rivers don’t run on the tops of mountains to deposit gravels. And Daisy was more into shorts than into long jumps.
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