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.
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