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2014年职称英语考试补全短文练习题 Sleeping Giant Right now, an eruption is brewing in Yellowstone National Park. Sometime during the next two hours, the most famous geyser. Old Faithful, will begin gurgling boiling water and steam._____1_____ Old Faithful is not only a spectacular sight; its also a constant remainder 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 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 professors, 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_____ | 
