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. "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 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 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 geological 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.