A super volcano is the most destructive force on this planet. Only a few exist in the world and when they erupt they do so with a force tens of thousands of times greater than other eruptions. They lie dormant for hundreds of thousands of years as a vast reservoir of magma builds up inside them before finally they unleash their apocalyptic force, capable of obliterating continents. They threaten the survival of mankind.
What happened during the last eruption of a super volcano?
The last eruption of a super volcano was in Toba, Sumatra, 75,000 years ago. It had 10,000 times the explosive force of Mount St. Helens and changed life on Earth forever. Thousands of cubic kilometres of ash was thrown into the atmosphere - so much that it blocked out light from the sun all over the world. 2,500 miles away 35 centimetres of ash coated the ground. Global temperatures plummeted by 21 degrees. The rain would have been so poisoned by the gasses that it would have turned black and strongly acidic. Man was pushed to the edge of extinction, the population forced down to just a couple of thousand. Three quarters of all plants in the northern hemisphere were killed.
What causes super volcanoes?
Super volcanoes differ from normal volcanoes in many ways. The stereotypical volcano is a towering cone, but super volcanoes form in depressions in the ground called calderas. When a normal volcano erupts lava gradually builds up in the mountain before releasing it. In super volcanoes when magma nears the surface it does not reach it, instead it begins to fill massive underground reservoirs. The magma melts the nearby rock to form more extremely thick magma. The magma is so viscous that volcanic gasses that normally trigger an eruption cannot pass, so a massive amount of pressure begins to build up. This continues for hundreds of thousands of years until an eruption occurs, which blasts away a huge amount of ground, forming a new caldera.
Where are there other super volcanoes?
Not all super volcanoes have been found, but one of the largest is in Yellowstone Park, USA. Scientists searching for the caldera in the park could not see it because it was so huge - only when satellite images were taken did the scale of the caldera become apparent - the whole park, 85km by 45km, is one massive reservoir of magma. The idyll landscape of Yellowstone (below) could soon explode with devastating consequences.
When will it next erupt?
Scientist have discovered that the ground in Yellowstone if 74cm higher than in was in 1923 - indicating a massive swelling underneath the park. The reservoir is filling with magma at an alarming rate. The volcano erupts with a near-clockwork cycle of every 600,000 years. The last eruption was more than 640,000 years ago - we are overdue for annihilation.
What would be the effect of an eruption?
Immediately before the eruption, there would be large earthquakes in the Yellowstone region. The ground would swell further with most of Yellowstone being uplifted. One earthquake would finally break the layer of rock that holds the magma in - and all the pressure the Earth can build up in 640,000 years would be unleashed in a cataclysmic event.
Magma would be flung 50 kilometres into the atmosphere. Within a thousand kilometres virtually all life would be killed by falling ash, lava flows and the sheer explosive force of the eruption. Volcanic ash would coat places as far away as Iowa and the Gulf of Mexico. One thousand cubic kilometres of lava would pour out of the volcano, enough to coat the whole of the USA with a layer 5 inches thick. The explosion would have a force 2,500 times that of Mount St. Helens. It would be the loudest noise heard by man for 75,000 years, the time of the last super volcano eruption. Within minutes of the eruption tens of thousands would be dead.
The long-term effects would be even more devastating. The thousands of cubic kilometres of ash that would shoot into the atmosphere could block out light from the sun, making global temperatures plummet. This is called a nuclear winter. As during the Sumatra eruption a large percentage of the world's plant life would be killed by the ash and drop in temperature. Also, virtually the entire of the grain harvest of the Great Plains would disappear in hours, as it would be coated in ash. Similar effects around the world would cause massive food shortages. If the temperatures plummet by the 21 degrees they did after the Sumatra eruption the Yellowstone super volcano eruption could truly be an extinction level event.