下面的短文有5处空白，短文后有6个句子，其中5个取自短文，请根据短文内容将其分别放回原有位置，以恢复文章原貌。 Sleeping Giant Right now, an eruption is brewing (酝酿) in Yellowstone National Park (黄石国家公园). Sometime during the next two hours, the park’s most famous geyser(间歇泉), Old Faithful, will begin gurgling (潺潺地流) boiling water and steam. (46) Old Faithful is not only a spectacular sight; it’s also a constant reminder that Yellowstone sits on one of the largest volcanoes in the world. If you have never heard of Yellowstone’s volcano, you are not alone. (47) Yet it has erupted three times during the last 2 million pears. And one of those eruptions spewed (喷涌) enough volcanic ash and other debris to blanket half the United States. Yellowstone’s volcano is sometimes called a "super volcano", or extremely large and explosive calderas(破火山口)volcano. (48) This super volcano formed over a hot spot, an extremely hot area in Earth’s mantle(地幔). 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(大陆的) crust, which may cause catastrophic (灾难性的) 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 and blanketed most of the western half of the United States. (49) 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(可变性的), so we don’t really know when the next eruption will happen. " (50) It is the volcanic energy that powers the geysers and hot springs, creates the mountains and canyons(峡谷) and generates the unique ecosystems that support Yellowstone’s diverse wildlife. 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 (不显眼的) 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 at trams the interest of geologists the world over.