2022年职称英语卫生类A级补全短文练习题14Old Faithful is not only a spectacular sight;its also.a constant reminder that Yellowstone sits on one of the largest volcanoes in the world.If youve never heard of Yellowstones volcano，youre not alone. 2 Yet it has erupted three times during the last 2 million years.And one of those eruptions spewed enough volcanic ash and other debris to blanket half the United States. Yellowstones volcano is sometimes called a “supervolcano，” or extremely large and explosive caldera volcano. 3 .This supervolcano formed over a hot spot.an extremely hot area in Earths mantle.John Valley，a volcano professor，said that as the crust moves across a hot spot，the hot spot melts a section of the plate moving over it.Forming “one volcano after another.” The Yellowstone hot spot melts thick continental crust，which may cause catastrophic eruptions.According to experts the eruptions that created each of the three calderas in and around Yellowstone National Park were larger than any other volcanic eruption in recorded history.The most recent eruption，which happened 640，000 years ago，produced at least 1.000 cubic kilometers of ash and debris，which blanketed most of the western half of the United States. 4 Geological evidence shows Yellowstone has blown its stack every 700，000 years or so.“If nature were truly that regular and reliable，we would be due for another eruption soon,” said Valley “However，these processes are subject to variability, so we dont really know when the next eruption will happen.” 5 It is the volcanic energy that powers the geysers and hot springs.creates the mountains and canyons.and generates the unique ecosystems that support Yellowstones diverse wildlife. 练习： A. Three calderas make up more than a third Of Yellowstone National Park. B. The first Yellowstone eruption，2 million years ago，released more than double that amount of ash and debris. C.The volcano is so inconspicuous(不惹眼的)that few people know it exists. D.Then, an enormous fountain will shoot high into the air. E.While the active geologist processes at Yellowstone do pose some risk to the public，they also make it a unique treasure. F.Yellowstone National Park attracts the interest of geologists the world over 答案： D,C,A,B,E