After 400 years of dormancy, Indonesia’s Mount Sinabung has woken up from its slumber with an eruption that has already displaced 30,000 people. A volcano is an opening, or rupture, in a planet’s surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface. Volcanoes are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth’s crust in the interiors of plates, e.g., in the East African Rift, the Wells Gray-Clearwater volcanic field and the Rio Grande Rift in North America. This type of volcanism falls under the umbrella of “Plate hypothesis” volcanism. Intraplate volcanism has also been postulated to be caused by mantle plumes. These so-called “hotspots”, for example Hawaii, are postulated to arise from upwelling diapirs from the core-mantle boundary, 3,000 km deep in the Earth
A supervolcano is a large volcano that usually has a large caldera and can potentially produce devastation on an enormous, sometimes continental, scale. Such eruptions would be able to cause severe cooling of global temperatures for many years afterwards because of the huge volumes of sulfur and ash erupted. They are the most dangerous type of volcano. Examples include Yellowstone Caldera in Yellowstone National Park and Valles Caldera in New Mexico (both western United States), Lake Taupo in New Zealand, Lake Toba in Sumatra, Indonesia and Ngorogoro Crater in Tanzania, Krakatoa near Java and Sumatra, Indonesia. Supervolcanoes are hard to identify centuries later, given the enormous areas they cover. Large igneous provinces are also considered supervolcanoes because of the vast amount of basalt lava erupted, but are non-explosive.
The Top 10 Volcanoes in The World
- Mount Vesuvius Mt. Vesuvius, the active volcano that looms over the Bay of Naples in southern Italy, has erupted well over 30 times that we know of. And yet its most famous eruption took place all the way back in A.D. 79, when a multiday eruption of lava and ash covered the cities of Pompeii and Stabiae in ash. Pliny the Younger, author of the only surviving eyewitness account, described a sudden explosion followed by blankets of ash that fell on people as they tried to escape. The total number of Vesuvius’ victims will most likely never be known, but archeologists are aware of at least 1,000.
- Krakatoa. In 1883, the volcano on the Indonesian island of Krakatoa erupted with 13,000 times the power of an atomic bomb. The sound of the spewing smoke and rock was reportedly heard thousands of miles away, as far as islands off the eastern coast of Africa. Hundreds in a nearby Sumatran town died almost instantly when flaming ash incinerated their homes, and many more were washed away by subsequent megatsunamis. An estimated 36,000 or so perished in total. Krakatoa itself then slumped into the boiling depths of the ocean, but a new island at the site was spotted in 1927, and it still occasionally spits lava into the sky. It’s been dubbed Anak Krakatoa, or Child of Krakatoa
- Mount St. Helens.Mount St. Helens was getting ready to burst for nearly two months before it exploded, not to mention the more than 120 years it lay dormant. While the eruption was anticipated, the manner in which it occurred was completely unprecedented. At 8:32 a.m. on May 18, 1980, a 5.1-magnitude earthquake triggered a sideways blast that swept the mountain’s north face away into a cascading landslide that shot hot ash and stone out some 15 miles at speeds of at least 300 m.p.h. At the same time, a mushroom-shaped plume of ash shot 16 miles into the air, eventually covering three states. Complete darkness blanketed Spokane, Wash., a city about 250 miles northeast of the volcano. When the ash came down it fell in the form of black rain that literally coated the residents of Washington, Idaho and parts of Montana with a fine gray powder. Fifty-seven people and thousands of animals were killed, and some 200 square miles of trees were obliterated. In 1982, Congress and President Ronald Reagan designated the surrounding land as the Mount St. Helens National Volcanic Monument
- Mount Tambora. The Volcanic Explosivity Index goes up to 8. On that scale, the 1815 eruption of Mount Tambora rates a very destructive 7. The explosion took place on the island of Sumbawa (then in the Dutch East Indies, now in Indonesia) and plunged the region into darkness, but its effects were anything but isolated. Tens of thousands of people were killed by the apocalyptic eruption, subsequent tsunamis and ensuing starvation and disease. The largest volcanic eruption in recorded history changed the world’s climate so much (even crops in Europe and North America failed) that 1816 became known as “the year without a summer.” Tambora itself shrank several thousand feet and traded its peak for a massive crater at its summit.
- Mauna Loa, It’s fitting that the state created out of a chain of volcanic islands would be home to the world’s largest volcano. Mauna Loa is located on the Big Island of Hawaii and in addition to being the largest, with a summit nearly 13,700 feet high, it is also one of the world’s most active. Since 1843, Mauna Loa has erupted 33 times, most recently in 1984. At 60 miles long and 30 miles wide, Mauna Loa, the name of which fittingly means “Long Mountain” in Hawaiian, takes up about half of the Big Island. Its mass also amounts to 85% of all the other Hawaiian Islands combined.
- Eyjafjallajokull.It was like an overly contrived disaster flick: A mammoth cloud of ash from an Icelandic volcano creeps across the European continent, shutting down airports and stranding hundreds of thousands for days. Across the globe, people curse the volcano — or attempt to, since few can actually pronounce the name Eyjafjallajokull. And despite all our technological prowess, human ingenuity is shown to be futile in the face of an ash plume.
Eyjafjallajokull, whose name means “Island Mountain Glacier” in Icelandic, first erupted this year on March 20. But it was the eruption that began April 14 that wrought all the havoc, ultimately costing the airline industry more than $1 billion
- Mount Pelée.
Mount Pelée, standing more than 4,500 feet high on the French Caribbean island of Martinique, erupted violently in May 1902, killing nearly 30,000 people — effectively the entire port city of St. Pierre. The catastrophe was so devastating that the term pelean — to describe that particular kind of ash, gas and fiery cloud eruption — became part of volcanic vernacular. There had been warnings of steam, light earth shocks and raining ash, but they were ignored. After the town was wiped out, Pelée went dormant for some months, until geologists discovered a lava dome, dubbed the tower of Pelée, that rose to more than 1,000 feet above the crater floor before eventually crumbling in March 1903
- Thera.Some 3,500 years ago, an event of cataclysmic proportions rocked the Mediterranean. The volcano at Thera (later known as the Greek island of Santorini) exploded with what is estimated at four to five times the eruptive force of Krakatoa in 1883, blowing a hole into the Aegean isle and sending out shock waves that, according to historians, would reverberate for centuries to come. The great seafaring Minoan civilization, the dominant Greek culture of the time, potentially withered away after clouds of ash enveloped its cities and great tsunami waves smashed its fleets. Stories of a world-shaking eruption linger in legends across the Mediterranean. For years, adventure-seeking archaeologists have even pored through Thera’s geological record in search of the fabled lost city of Atlantis. Ancient Egyptian stela from roughly the same era chronicle a volcanic storm that “caused darkness in the Western region” and “annihilated” towns and temples alike. And some biblical scholars have even suggested Thera’s destructive effects underlie the Old Testament’s tales of God-sent plagues and devastation.
- Nevado del Ruiz. The eruption was small — in volcanic terms, that is — producing only about 3% of the ash ejected by Mount St. Helens in 1980. Instead, it was the mudflows that made Colombia’s 1985 Nevado del Ruiz explosion the second deadliest in the 20th century and the fourth deadliest in recorded history. The volcano has been blowing its top since the Pleistocene era and has erupted three times in modern history, including in 1595 and 1845. But on Nov. 13, 1985, a relatively small explosion unleashed floods that swept away 1,500 people on one side of the mountain. On the other side was the town of Armero, the site of the worst destruction. 25-m.p.h. lahars (volcanic mudflows) obliterated the town and blanketed it in gray muck. When the landslides subsided, 23,000 people had died and damage was estimated at $1 billion — one-fifth of Colombia’s GNP at the time.
- Mount Pinatubo. When Mount Pinatubo erupted in 1991, the amount of sulfuric ash it sent into the stratosphere cooled global ground temperatures by 1°F for the next two years. To be fair, it hadn’t erupted for six centuries, so there was some catching up to do. A year before the eruption, a 7.8-magnitude earthquake struck about 60 miles northeast of Pinatubo, causing landslides and an increase in steam emissions from one of the volcano’s geothermal areas, ultimately setting the stage for the 1991 explosion. While the eruption resulted in more than 700 deaths, many scientists predicted the explosion, thus saving the lives of an estimated 5,000. Still, the eruption produced one of the most dramatic environmental scenes ever witnessed. With ash that rose 22 miles into the sky, it is considered the second largest volcanic eruption of the 20th century.
source : BBC
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