Sleeping Giant
Right now, an eruption is brewing in Yellowstone National Park. Sometime during the next two hours, the park's most famous geyser, Old Faithful, will begin gurgling boiling water and steam. ____1____
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've never heard of Yellowstone's volcano, you’re 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.
Yellowstone's 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 Earth's 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.1 “If nature were truly that regular and reliable, we would be due for another eruption soon,2” said Valley. "However, these processes are subject to variability, so we don't 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 Yellowstone's diverse wildlife3.
詞匯：
brew 醞釀
Yellowstone National Park黃石國家公園
geyser 間歇泉 gurgle 汩汩地流 spew 噴涌
caldera 火山口洼地 crust 地殼
mantle 地幔 continental 大陸的
catastrophic 災難的 variability 可變性 canyon 峽谷