Source: United States Geological Survey, University of Utah, The BBC
Super Volcano In Yellowstone National Park
It is little known that lying underneath one of The United States largest and most picturesque National Parks - Yellowstone Park - is one of the largest "super volcanoes" in the world.
The term "super volcano" has no specifically defined scientific meaning. It was used by the producers of The BBC TV show Horizon in 2000 to refer to volcanoes that have generated Earth's largest volcanic eruptions. As such, a super volcano would be one that has produced an exceedingly large, catastrophic explosive eruption and a giant caldera.
Scientists have revealed that Yellowstone Park has been on a regular eruption cycle of 600,000 years. The last eruption was 640,000 years ago…so the next is overdue. The next eruption could be 2,500 times the size of the 1980 Mount St. Helens eruption. Volcanologists have been tracking the movement of magma under the park and have calculated that in parts of Yellowstone the ground has risen over seventy centimeters this century.
Around the world there are several other volcanic areas that can be considered "super volcanoes"- Long Valley in eastern California, Toba in Indonesia, and Taupo in New Zealand. Other "super volcanoes" would likely include the large caldera volcanoes of Japan, Indonesia, Alaska (e.g. Aniakchak, Emmons, Fisher).
Normal volcanoes are formed by a column of magma - molten rock - rising from deep within the Earth, erupting on the surface, and hardening in layers down the sides. This forms the familiar cone shaped mountain we associate with volcanoes.
Super volcanoes, however, begin life when magma rises from the mantle to create a boiling reservoir in the Earth's crust. This chamber increases to an enormous size, building up colossal pressure until it finally erupts. The explosion would send ash, dust, and sulfur dioxide into the atmosphere, reflecting the sun's rays and creating a cold wave lasting several years. Crops in many areas would fail and many species of animals and plants would face extinction.
Volcanic activity began in the Yellowstone National Park region a little before about 2 million years ago. Molten rock (magma) rising from deep within the Earth produced three cataclysmic eruptions more powerful than any in the world's recorded history. The first caldera-forming eruption occurred about 2.1 million years ago. The eruptive blast removed so much magma from its subsurface storage reservoir that the ground above it collapsed into the magma chamber and left a gigantic depression in the ground- a hole larger than the state of Rhode Island. The huge crater, known as a caldera, measured as much as 80 kilometers long, 65 kilometers wide, and hundreds of meters deep, extending from outside of Yellowstone National Park into the central area of the Park.
The most recent caldera-forming eruption about 650,000 years ago produced a caldera 53 x 28 miles (85 x 45 kilometers) across in what is now Yellowstone National Park (Figure 2). During that eruption, ground-hugging flows of hot volcanic ash, pumice, and gases swept across an area of more than 3,000 square miles. When these enormous pyroclastic flows finally stopped, they solidified to form a layer of rock called the Lava Creek Tuff. Its volume was about 240 cubic miles (1,000 cubic kilometers), enough material to cover Wyoming with a layer 13 feet thick or the entire conterminous United States with a layer 5 inches thick. The Lava Creek Tuff has been exposed by erosion at Tuff Cliff, a popular Yellowstone attraction along the lower Gibbon River.
The eruption also shot a column of volcanic ash and gases high into Earth's stratosphere. This volcanic cloud circled the globe many times and affected Earth's climate by reducing the intensity of solar radiation reaching the lower atmosphere and surface. Fine volcanic ash that fell downwind from the eruption site blanketed much of North America. This ash layer is still preserved in deposits as far away as Iowa, where it is a few inches thick, and the Gulf of Mexico, where it is recognizable in drill cores from the sea floor. Lava flows have since buried and obscured most of the caldera, but the underlying processes responsible for Yellowstone's tremendous volcanic eruptions are still at work.
TINY CRYSTALS PREDICT A HUGE VOLCANO IN WESTERN U.S.
MADISON - Reading the geochemical fine print found in tiny crystals of the minerals zircon and quartz, scientists are forming a new picture of the life history - and a geologic timetable - of a type of volcano in the western United States capable of dramatically altering climate sometime within the next 100,000 years.
With insight gained from new analytical techniques to study crystals of zircon and quartz, minerals that serve as veritable time capsules of geologic events, a group of scientists from the University of Wisconsin-Madison has proposed a new model for the origin of volcanism in young calderas.
These are volcanoes that occur over "hot spots" in the Earth and they erupt every few hundred thousand years in catastrophic explosions, sending hundreds to thousands of cubic kilometers of ash into the atmosphere and wreaking climatic havoc on a global scale.
In a series of papers, UW-Madison geologists Ilya N. Bindeman and John W. Valley present a life history of the hot spot volcanism that has occurred in the Yellowstone basin of the western United States over the past 2 million years.
Today's Yellowstone landscape represents the last in a sequence of calderas - the broad crater-like basins created when volcanoes explode and their characteristic cones collapse - that formed in regular progression over the past 2 million years. The near-clockwork timing of eruptions there - 2 million years ago, 1.3 million years ago and 600,000 years ago - suggests a pattern that may foreshadow an eruption of catastrophic proportions, said Bindeman and Valley.
Beneath Yellowstone and its spectacular landscape of hot springs and geysers is a hot spot, an upwelling plume of melted rock from the Earth's mantle. As the plume of hot, liquid rock rises in the Earth, it melts the Earth's crust and creates large magma chambers.
"These magmas usually erupt in a very catastrophic way," said Bindeman. "By comparison, the eruption of Mount St. Helens sent about two cubic kilometers of ash into the atmosphere. These catastrophic types of eruptions send thousands of cubic kilometers of ash skyward."
The hot spot deep beneath Yellowstone acts like a burner, said Bindeman. "It's a constant source of heat that acts on the upper crust and forms magma chambers that contain tens of thousands of cubic kilometers" of molten rock.
One of the massive plates that helps make up the crust of the Earth, the North American plate, is slowly moving over the hot spot, said Bindeman. "The plate has been moving across the heat source which makes it seem like the volcanoes are moving across the continent. Moreover, we have a progression of explosive eruptions which seem to have some periodicity."
Bindeman and Valley studied rocks that span the entire 2-million-year long eruptive sequence at Yellowstone with a special emphasis on lavas that erupted the last time one of the massive volcanoes popped off creating what geologists call the Yellowstone Caldera. Their conclusion is that the volcanic cycle is waning, but that there is still a very real potential of an eruption of massive proportions sometime in the near geologic future.
A cross section of a quartz crystal obtained from rocks near Yellowstone. Crystals of quartz and zircon harbor geochemical clues to past -- and future -- volcanic eruptions in the Yellowstone caldera. In the past, eruptions over this "hot spot" in the Earth have been of a magnitude that would have severely altered Earth's climate.
The most recent caldera is 600,000 years old and encompasses an area of more than 2,000 square kilometers. When it erupted, it blasted 1,000 cubic kilometers of volcanic rock into the atmosphere and it settled as ash over more than half of the United States.
After that last major eruption, volcanism in Yellowstone continued in a quieter fashion with another, much smaller eruption occurring 70,000 years ago.
Old Faithful Geyser Yellowstone National Park
Today's spectacular geysers and hot springs at Yellowstone are the most visible part of the volcanic system there. They contain heated snow and rainwater which leave a geochemical record that provides insight into the region's geologic activity. Prior to the last catastrophic eruption at Yellowstone 600,000 years ago, an even more spectacular geothermal landscape existed there, said Bindeman.
"The unique thing about Yellowstone is that the volcanic rocks that erupted following the collapse of the big calderas contain up to 50 percent oxygen which was ultimately derived from rain waters," Bindeman said. "The zircon and quartz tell us that rocks near the surface were altered by heated snow and rainwater. These rocks were then remelted to become magmas."
This scenario changes the view of magmatism at Yellowstone and other calderas as representing new magma coming from deep in the Earth. On the contrary, Bindeman and Valley make a case for the total remelting and recycling of previously erupted surface rocks.
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