Supervolcanoes of our Earth
Supervolcanoes are invisible
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The supervolcanoes have a flat structure and it is difficult to detect. Only after ordnance, when the underground magma chamber collapses, which can be seen, the famous caldera in the soil. These calderas of several tens of km, are so great that it can not detect that from an aerial view. The supervolcanoes as volcanoes are located in areas of intense geologic activity, earthquakes, eruptions of volcanoes and mountain building. These zones define the boundaries between lithospheric plates (7 large and 20 small plates). Volcanoes and supervolcanoes, located along the tectonic zones. The main tectonic plates earthquakes delineate lines. Among these plates, we find the plate of North America, South America, Eurasia, Africa, Pacific, Australia and Antarctica. The supervolcanoes cause for great eruptions that have nothing to do with the classic rash that is usually observed on Earth. Humanity has not yet attended a super eruption. These super eruptions can create considerable damage to the scale of a continent and have cataclysmic effects for life on Earth. The most recent explosion of a supervolcano listed, dated around 26 500 years is that of Lake Taupo in New Zealand.
The eruption of the Indonesian supervolcano, Toba on the island, there are about 73 000 years, spewed massive amounts of ash, estimated at nearly 2800 cubic km. By comparison, the eruption of Mount Pinatubo in the early 1990s, has issued only 10 cubic kilometers of ash. The ashes of Pinatubo have changed the albedo of the Earth and brought down its mean temperature 0.6 ° C for two years.
In 1998, a professor of anthropology at the University of Illinois, Stanley Ambrose, said the eruption of Toba caused a global cooling of the planet for 1800 years. The supervolcanoes are mostly extinct.
NB: VEI: enables a relative measure of explosive volcanic eruptions.
This index volcanic explosion, or VEI, English Volcanic Explosivity Index, was invented by Chris Newhall of the U.S. Geological Survey, and Steve Self at the University of Hawaii in 1982.
Image: Classification des éruptions volcaniques (VEI, Volcanic Explosivity Index).
||< 100 m
||100 m - 1 km
||> 30 km
||> 40 km
||> 50 km
|nota : VEI 8 = Lac Taupo 26,500 years ; Toba 74,000 years ; Yellowstone 600,000 years.
Toba - Indonesia
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Toba is located on the island of Sumatra, on the subduction zone between the Indo-Australian Plate and Eurasian.
The supervolcano the island of Toba in Indonesia is the subject of a catastrophic theory on human evolution by Stanley Ambrose, a professor at the University of Illinois at Urbana-Champaign.
Volcanoes can cause massive climate disasters, causing a sudden cooling of the Earth's mean temperature. The eruption of the Indonesian supervolcano, Toba on the island, there are about 73 000 years, spewed massive amounts of ash, estimated at about 2,800 cubic km, falling to 3,100 km from the volcano.
In 1998, Stanley Ambrose, said the eruption of Toba caused a global cooling of the planet for 1800 years. This eruption would have plunged the Earth into a volcanic winter.
A recent theory of American anthropologists, including Dr. Stanley H. Ambrose of the University of Illinois, believes that this disaster is causing a drastic decrease (genetic bottleneck), the population of hominids on Earth, then a revival from a small group of survivors. This would explain the unique genetic heritage of humanity. This theory is known as the theory of Toba catastrophe.
Image: Nestled in the heart of the rainforest of Sumatra, the caldera of the island of Toba has impressive dimensions. With its 30 km wide and 100 km long, the caldera is one of the largest in the world. The ancient caldera is filled by a lake in the middle of which the island of Samosir, embodying the old dome of the volcano.
Index VEI = 8, there 73 000 years
The caldera of Santorini in Greece
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The volcanic island of Santorini (the Venetian name Santa Irina - St. Irene), located in the Aegean, is composed of five apparently separate islands.
The site has a circular shape, which corresponds to the central portion (caldera) of a collapsed volcano, which exploded in Minoan times.
The ancient island Kallista was partially destroyed around 1628 BC. AD The remains of this eruption, causing the disappearance of the Minoan civilization, are now islands of Santorini, and Thirasia Aspronissi.
This cataclysm is the ancient origin of the Myth of Atlantis.
The perimeter of the ancient volcano gave the main island Thera (Fira delivered) to the west you can see and the island of Therasia Aspronisi.
Recent volcanic eruptions (16th and 17th century) created in the middle of the caldera, Palea Kameni and Nea Kameni (dark center of the image).
The beautiful scenery of the white villages perched on cliffs overlooking the caldera red SANTORINI, home despite the danger, a few thousand people.
Recently, in 1956, the island of Santorini was shaken by an earthquake which caused a further collapse of the crater of the hat.
This catastrophe made a fifty people and destroyed over 2,000 homes. The largest volcanic cone of Nea Kameni in the center of the archipelago is made entirely of black slag.
The volcanic explosion that took place there nearly 3,500 years, has carved the caldera, now considered a natural wonder known for its beautiful scenery, for its amazing sunsets from the town of Oia.
Image: Satellite image of the archipelago of Santorini, the island of Santorini with the right. This incomplete ring of 8 km in diameter and 85 km2, circumscribed islands of Thera and Therasia, which are remnants of ancient island before the collapse Kallista created this volcanic caldera.
Index VEI = 6, in 1600 BC
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Yellowstone - United States
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Yellowstone National Park is located in the Northwest United States. It is located near the Rocky Mountains. The Yellowstone area is the result of a massive eruption, which dates back to 642 OOO years.
It has been lively earthquake phenomena more discreet. The super-eruption of Yellowstone, has projected 1000 cubic kilometers of rock, the roof of the magma chamber was then collapsed, forming a box collapse called "caldera" which now comprises the central part of the park.
Since then, numerous minor eruptions filled the caldera, but we can still see the steep banks. Remains very active volcanism in Yellowstone, there are about 300 active geysers. The lava continues to accumulate, making new swell and shake the earth's crust. At the bottom of the current housing collapse, the altitude rose 70 cm during the past 50 years.
Since 2004, parts of the caldera rose up to 7 cm per year, the average elevation is 1 cm/yr.
"This is an extraordinary rise, because it covers a large area and the rates are very high, " said Bob Smith, a longtime expert in volcanism of Yellowstone from the University of Utah. The Yellowstone caldera is a crater formed after the last great explosion, there are 640 000 years. It extends from 40 to 60 km in a relatively flat landscape. The underground magma chamber is over 70 km wide and over 10 km high. Inside bubbling magma at a temperature of 1500 ° C. At Yellowstone the Earth's crust is only 7 to 10 kilometers thick, which explains the surface deformation.
Image: The Yellowstone supervolcano.
Index VEI = 8, there was 642 000 years