Super volcanoes how many

A volcano doesn't need to have a super-eruption to be dangerous; if people are nearby as it explodes, even small eruptions pose many hazards. That said, not all volcanic eruptions are dangerous.

If an eruption takes place far from populations and flight paths, no one may even notice that the peak burst its top. Supervolcanoes can occur in many situations. Some, like Yellowstone, can be due to hot spots, rising plumes of magma from deep inside Earth.

Hot spots generate a trail of volcanoes as the ever-moving tectonic plates slowly march across the largely stationary plume, like the lengthy chain of volcanoes of the Hawiian Islands. Others, like Toba in Sumatra, Indonesia , can form along subduction zones where one tectonic plate plunges beneath another.

As the descending landmass sinks deep underground, temperatures and pressures climb, forcing the water from the rocks. That water reduces the melting point of the overlying rocks, forming magma that can fuel future eruptions. Regardless of how the magma forms, however, a volcano needs a lot of it to produce a super-eruption. As the magma builds, pressure in the underground cavity increases. A super-eruption requires tons of pressure to actually jettison the huge pockets of molten rock through the surface.

While a super-eruption would no doubt be devastating, it wouldn't be a world-ending affair. For an idea of the effects of such an eruption, we could look to the explosion of Mount Tambora in Indonesia. At a VEI of 7, this explosion was not quite a super-eruption, but it gives a sense of the many dangers of such mega-blasts. The explosion sent a superheated plume of hot ash and gas 28 miles into the air, upon its collapse producing searing avalanches known as pyroclastic flows.

Such immediate hazards killed around ten thousand people, but that wasn't the only concern. The gasses and ash injected into the atmosphere darkened the skies, blotted out the sun, and altered the climate, resulting in what became known as the year without summer. Extensive crop failures, starvation, and disease followed, which killed around 82, more people.

What's most important to keep in mind about modern eruptions is that agencies around the world are keeping a close watch on supervolcanoes like Yellowstone, monitoring their every tremor and magma-laden belch. Volcanoes provide some notice of pending eruption and modern equipment helps scientists take their pulse with more accuracy than ever before. So while a super-eruption in the near future is exceedingly unlikely, these agencies will be the first to know and alert the public if one ever becomes imminent.

All rights reserved. Supervolcanoes What are supervolcanoes, and how catastrophic can they be? Learn how supervolcanoes form, where supervolcanoes are located, and how their destructive capabilities can make way for new life. Where did the term supervolcano come from? What about Yellowstone? Share Tweet Email. Read This Next Wild parakeets have taken a liking to London. And the fallout would extend for hundreds of kilometers, so any cities nearby a supervolcano are immediately toast.

As are any planes that attempt to fly people away from the danger. And keep in mind that ash travels. When Toba erupted 74, years ago, winds blew ash all the way to India. So if all the supervolcanoes go off at once, volcanic debris would spread across the globe. When the eruption ends, the disaster will have only just started. Because for the next six months, much of that supervolcanic ash would linger in the stratosphere and block sunlight, causing global temperatures to plunge by as much as 15 degrees Celsius.

That's close to the difference between summer in Rio versus Anchorage, Alaska. In fact, just "little" Mount Tambora's eruption alone set off the "Year Without a Summer," where frost and blizzards plagued much of the Northern Hemisphere.

So, multiply that by the 12 or so supervolcanoes all spewing thick black dust, and you've got a worldwide volcanic winter for the next few years. Tropical forests, which can't handle cold weather, would wither and die, bringing down the millions of animal species that live there. And it's about to get even bleaker. You know that saying "out of the frying pan and into the fire"? Well, in addition to ash, those volcanoes also belch toxic gasses, like sulfur dioxide, into the atmosphere.

And after a few years, just after the winter finally ends, those gasses would start to fall from the sky as acid rain. When the Laki volcano erupted in in Iceland, it rained down so much sulfuric acid that it devastated farmland and wiped out half of all livestock.

The next year, a full quarter of Iceland's population died in the resulting famine. Multimedia Gallery. Park Passes. Technical Announcements. Employees in the News. Emergency Management. Survey Manual. The term "supervolcano" implies a volcanic center that has had an eruption of magnitude 8 on the Volcano Explosivity Index VEI , meaning the measured deposits for that eruption is greater than 1, cubic kilometers cubic miles.

Comparison of eruption sizes using the volume of magma erupted from several volcanoes. Public domain. The VEI scale was created as a general measurement of the explosivity of an eruption. There are multiple characteristics used to give an eruption its VEI allowing for the classification of current and historic eruptions. The most common criteria are volume of ejecta ash, pumice, lava and column height. All VEI 8 eruptions occurred tens of thousands to millions of years ago making the volume of ejecta or deposits the best method for classification.

An eruption is classified as a VEI 8 if the measured volume of deposits is greater than 1, cubic kilometers cubic miles. Therefore a supervolcano is a volcano that at one point in time erupted more than 1, cubic kilometers of deposits. Yellowstone, like many other supervolcanoes, has also had much smaller eruptions. The cartoon shows a comparison of eruption sizes, including the three largest from Yellowstone. Click on the image for a more detailed description and larger view.

Volcanoes that produced exceedingly voluminous pyroclastic eruptions and formed large calderas in the past 2 million years would include Yellowstone, Long Valley in eastern California, Toba in Indonesia, and Taupo in New Zealand.

Other "supervolcanoes" would likely include the large caldera volcanoes of Japan, Indonesia, and South America. The most recent supervolcanic eruption on Earth occurred 27, years ago at Taupo located at the center of New Zealand's north island.

Not according to Bob Christiansen.