A supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruptions on earth. The actual explosivity of these eruptions varies, but the sheer volume of extruded magma is immense enough to radically alter the landscape and severely impact global climate for years, with a cataclysmic effect on life.
What is a Super Volcano?
A supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruptions on earth. The actual explosivity of these eruptions varies, but the sheer volume of extruded magma is immense enough to radically alter the landscape and severely impact global climate for years, with a cataclysmic effect on life. The term was originally coined by the producers of a BBC Popular Science programme in 2002 to refer to these types of eruptions. Though there is no well-defined minimum size for a "supervolcano", there are at least two types of volcanic eruption that have been identified as supervolcanoes.
Since there is no firm definition of what a super volcano is, it's hard to say how many of them are found on the earth. Usually people list Long Valley in eastern California and Taupo in New Zealand as super volcano sites along with Yellowstone National Park. The last known explosion of what might be considered a super volcano was Toba in Indonesia. Toba erupted with a huge explosion about 74,000 years ago. The force of the explosion was estimated to be 10,000 more powerful than the blast that destroyed Mount St. Helens, in Washington.
Tremendous amounts of rock and ash were ejected into the air, blocking the sun for months. The temperature around the globe was thought to have plummeted as much as 21 degrees. Man was pushed to the edge of extinction, the population forced down to just a couple of thousand. Perhaps as much as 75% of plant life on the North American continent may have died out.
What causes a Super Volcano
A super volcano differs from a regular volcano in that there is often no mountain peak associated with it. In a regular volcano hot magma under pressure flows up from the depths of the earth. A hole forms in the surface and the magma, now lava, pours out. As it cools, it forms a cone that eventually builds up into a mountain. If the passage is blocked off, the pressure can build up in the mountaintop and explode with a monstrous force. That's what happened at Mount St. Helens. The pit formed by the explosion becomes the new caldera.
In a super volcano the magma is blocked from ever reaching the surface. Instead, the pressure just builds and builds until more and more rock in the area melts and becomes magma too. The area under the surface becomes one huge underground sea of semi-molton rock.
Finally, the pressure becomes too much to hold back and the entire surface above the underground chamber, which can be many miles wide, is blown away by a huge explosion that can be thousands of times more powerful than that of a regular volcano.
Super volcanoes are found throughout the world, there is even evidence to prove that there is a super volcano beneath Loch Ness, Scotland. Loch Ness lies on the Great Glen fault-line and its incredible depth (over 2km) has severely hampered researchers progress. Fortunately new developments with satellite laser topography sonar side-scanning techniques have enabled us to penetrate through the thick sludge that lies up to 400m thick at the loch's bottom.
The latest eruption of Mt. Etna in Sicily, which had destroyed a few buildings, shut down the airport and crept into a ski area, produces dramatic nighttime video of hot rolling lava and explosive fireworks. But compared to the known history of volcanoes and even its own past, Etna's 2001 pyrotechnic show is so far geologically pathetic.
Likewise, the eruption of Mt. St. Helens in 1980 was a volcanic sneeze compared to what scientists say America will experience one day. And a mysterious four-inch-high bulge in the ground of central Oregon is, so far, little more than a conversation piece.
Sooner or later, geologists warn, a "super volcano" will strike. Some scientists in this field will even go so far as to say that phenomena like this one pose a greater threat than terrorism.
When will one next erupt?
Scientist have discovered that the ground in Yellowstone is over 70cm higher than in was in 1923 - indicating a massive swelling underneath the park. The reservoir is filling with magma at a staggering rate. The volcano erupts with a calendar-like cycle of every 600,000-650,000 years. The last eruption was more than 640,000 years ago - we could be running late.
What would be the effect of an eruption?
Let's use Yellowstone. Immediately before the eruption, there would be large earthquakes in the region. The ground would swell further with most of the area 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 more than 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 cover places thousands of miles away. One thousand cubic kilometres of lava would pour out of the volcano itself, enough to coat the whole of the USA with a layer a few inches thick. The explosion would have a force 1000-2500 times that of Mount St. Helens. It would be the loudest noise heard by man for more than 75,000 years, the time of the last super volcano eruption. Within minutes of the eruption tens of thousands could 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 fall dramatically. 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 severe drop in temperature. Effects world wide would cause massive food shortages. If the temperatures decline by the 21 degrees they did after the Sumatra eruption the Yellowstone super volcano eruption could truly be an extinction level event.
Humans could be pushed to the edge of extinction. Anthropologists suggest it won't be the first time.
But well before such a calamity, warning flags will likely show up on the computers of geologists around the world who monitor an increasingly useful stream of satellite data. There have also been more pushes by scientists in the field to 'wake up' and devote more attention to this, it's truly startling.
