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Sleeping Calderas

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The Super Volcanos Under Our Feet

By James Donahue

Among the popular tourist spots in North America is Yellowstone National Park, where people come to camp, fish, and see the wonders of geysers, hot bubbling mud, and walk among hot steamy pools where gasses that smell of sulfur spew from below their feet.

The park has remained this strange hot bubbling place for as long as humans have been around to record its history, so nobody considers it dangerous. Yet geologists who study such places say Yellowstone is a super volcano that has the potential of blowing its top and consuming much of the United States with it when it happens.

Some believe that Yellowstone is a volcano so powerful, with a dome covering acres of mountain territory, that is it ever wakes up and blows, the explosion of molten lava, rock and gas could be so massive that it will have the capacity to destroy most of all life on Earth.

So how dangerous is such a super volcano? It is said that they only blow up every few hundred thousand years so the odds against it happening in our time are very low. Yellowstone last blasted off about 640,000 years ago. But there are six other known super volcanos in existence. And if one of them does blow an eruption of that size can spew enough ash into the atmosphere to cool the world’s climate by several degrees Celsius.

So what could we expect if such a volcano exploded? One report said there would be massive earthquakes, the ground would swell, and once the magma, rock and ash is unleashed, it would be flung 50 kilometers into the atmosphere. It would be the loudest noise ever heard by man.

All life would be immediately killed within a thousand kilometers by falling ash, lava flows and the explosive force of the eruption. Volcanic ash would fall for thousands of miles. There would be enough from Yellowstone to coat the entire United States with five inches of ash.

The long-term effects would be even worse. Thousands of cubic kilometers of ash would remain in the stratosphere for months if not years, blocking out the light of the sun and cooling the planet. We would experience a so-called nuclear winter. A large portion of the plant life all over the world would die from the ash and the cold. There would be such massive food shortages that people who survived the blast would starve. The destruction could, indeed, threaten world extinction.

Where are the other super volcanos? Believe it or not, two others exist in the United States.

A 200-square-mile caldera, said to be almost as huge as Yellowstone, is the Long Valley caldera just south of Mono Lake in east-central California, near the Nevada state line. Geologists speculate that this one erupted last about 760,000 years ago. When that happened, the caldera floor dropped about a mile. Like Yellowstone, this super volcano has been showing signs of waking up since the early 1900s. There have been strings of minor earthquakes, the caldera floor has been rising and carbon dioxide gas from the magma below has been seeping up and killing trees. Trouble here may be close….but that may still mean years away.

In northern New Mexico the third super volcano, the Valles caldera which spans 175-square miles just west of Santa Fe, also offers active hot springs, a clear sign of heat below. It was said to have exploded for the last time about 1.2 million years ago.

In the Greek/Italian area, a caldera of boiling mud and sulphurous steam holes known as the Campi Flegrei, west of Naples, has been a major tourist attraction, much like Yellowstone. But Geologists agree this is also a super volcano with enough potential magma and explosive gas trapped below to plunge the Earth into darkness if it ever blows. This is especially troublesome because, unlike the super volcanos in the Western United States, an estimated 3 million people live under its shadow.

Another huge super volcano is the Toba caldera in North Sumatra, Indonesia, which boasts a 1,080-square-mile caldera. It last erupted about 74,000 years ago with a blast so powerful its effect appears to be seen in the human genome, researchers say. Our genes suggest that we all are descendants of a few thousand people who lived about tens of thousands of years ago. Were they the sole survivors of an eruption by the Toba super volcano?

In New Zealand lies another massive caldera known as Taupo. The last time it blew, an estimated 1980 years ago, it left a lake where the mountain used to be. Yet they say Taupo is still active. The caldera is 485 square miles wide and there are hot springs and steam vents in the area.

Last but not the least of the super volcanos is Aira, a 150-square-mile caldera near the City of Kagoshima, Japan. The last time this volcano roared, about 22,000 years ago, it formed Kagoshima Bay. A volcano, Sakura-jima, which is part of the caldera, has been active during the last 100 years and earthquakes frequently occur there. Thus this caldera is believed to still be active.