Is The Forecasting Of The Eruption Of The Yellowstone Supervolcano Possible?
Plus: Mega-tsunami: Wave of Destruction Threatens The Whole East Coast
Robert B. Trombley, Ph.D.
Southwest Volcano Research Centre
Supervolcanoes are eruptions and explosions of catastrophic proportions. These types of eruptions are absolutely apocalyptic in scale. It is difficult to imagine an eruption this tremendous. The main factor governing the size of this type of eruption is the amount of magma available. If an enormous amount of magma has accumulated in the crust, then you have the potential for a very , very large eruption.
The exact geological conditions needed to create a vast magma chamber exist in only a very few places on earth, so there are only a few known supervolcanoes in the world. The last one to erupt was Toba 74,000 years ago [Rampino, Self, 2000). No modern human has ever witnessed a supervolcano eruption. Volcanologists are not even sure where all the supervolcanoes are but one that is known is Yellowstone National Park.
Yellowstone is America's first and most famous National Park. Every year over 3 million tourists visit this stunning wilderness, but beneath its hot springs and lush forests lies a monster of which most of the public is completely unaware [Smith, 1980].
Most people's idea of a volcano is a symmetrical cone and this involves magma coming up, reaching the surface, being extruded either as lava or as explosive eruptions with ash, and these layers of ash and lava gradually accumulate until you're left with a classic cone shape. We volcanologists know this smooth flowing magma contains huge quantities of volcanic gases, like carbon dioxide and sulfur dioxide. Because this magma is so liquid these gases bubble to the surface, easily escaping. There are thousands of these normal volcanoes throughout the world. Around 50 erupt every year, but supervolcanoes are very different in almost every way.
First, they look different. Rather than being volcanic mountains, supervolcanoes form depressions in the ground. Despite never having seen a supervolcano erupt, by studying the surrounding rock scientists have been able to piece together how supervolcanoes are formed. Like normal volcanoes they begin when a column of magma rises from deep within the Earth. Under certain conditions, rather than breaking through the surface, the magma pools and melts the Earth's crust turning the rock itself into more thick magma.
Although it is not clearly understood why, but in the case of supervolcanoes a vast reservoir of molten rock eventually forms. The magma here is so thick and viscous that it traps the volcanic gases, building up colossal pressures over thousands of years. When the magma chamber eventually does erupt its blast is hundreds of times more powerful than the normal draining of the underground reservoir. This causes the roof of this chamber to collapse forming an enormous crater. All supervolcano eruptions form these subsided craters. They are called calderas.
Such is the case with Yellowstone - it is the largest single active system yet discovered.
When Yellowstone goes off again, and it will, it will be a disaster for the United States and eventually, for the whole world. We volcanologists believe it would all begin with the magma chamber becoming unstable. Observations would begin by seeing bigger earthquakes, greater uplifting as magma intrudes and gets nearer and nearer the surface. An earthquake may send a rupture through a brittle layer similar to breaking the lid off a pressure cooker. This would generate sheets of magma, which will perhaps rise up to 30, 40 or 50 kilometers sending gigantic amounts of debris into the atmosphere. Pyroclastic flows would cover the whole region, killing tens of thousands of people in the surrounding area.
The ash carried in the atmosphere and deposited over vast areas of the United States would have devastating effects. A plume of material that goes up into the atmosphere, globally, from the eruption would produce the climatic effects. This would spread worldwide and have a cooling effect that would most likely destroy the growing season on a global scale.
As Dr. Ted Nield, of the Geological Society of London, stated once, "When a supervolcano goes off, it is an order of magnitude greater than a normal eruption. It produces energy equivalent to an impact with a comet or an asteroid." "You can try diverting an asteroid, but there is nothing at all you can do about a supervolcano."
The eruption will throw out cubic kilometers of rock, ash, dust, sulfur dioxide and so on into the upper atmosphere, where it will reflect incoming solar radiation, forcing down temperatures on the earth's surface. It would be the equivalent of a nuclear winter. The effects would last for four or five years with crops failing and the whole ecosystem breaking down.
Mega-tsunami: Wave of Destruction Threatens The Whole East Coast
BBC Two 9.30pm 12 October 2000
Revisited: BBC Four 10pm 25 October 2002
Scattered across the world's oceans are
a handful of rare geological time-bombs. Once unleashed they create an extraordinary
phenomenon, a gigantic tidal wave, far bigger than any normal tsunami, able to
cross oceans and ravage countries on the other side of the world. Only recently
have scientists realised the next episode is likely to begin at the Canary Islands,
off North Africa, where a wall of water will one day be created which will race
across the entire Atlantic ocean at the speed of a jet airliner to devastate the
east coast of the United States. America will have been struck by a mega-tsunami.
Back in 1953 two geologists travelled to a remote bay in Alaska looking for oil. They gradually realised that in the past the bay had been struck by huge waves, and wondered what could have possibly caused them. Five years later, they got their answer. In 1958 there was a landslide, in which a towering cliff collapsed into the bay, creating a wave half a kilometre high, higher than any skyscraper on Earth. The true destructive potential of landslide-generated tsunami, which scientists named "Mega-tsunami", suddenly began to be appreciated. If a modest-sized landslide in Alaska could create a wave of this size, what havoc could a really huge landslide cause?
Scientists now realise that the greatest danger
comes from large volcanic islands, which are particularly prone to these massive
landslides. Geologists began to look for evidence of past landslides on the sea
bed, and what they saw astonished them. The sea floor around Hawaii, for instance,
was covered with the remains of millions of years' worth of ancient landslides,
colossal in size.
But huge landslides and the mega-tsunami that they
cause are extremely rare - the last one happened 4,000 years ago on the island
of Réunion. The growing concern is that the ideal conditions for just such
a landslide - and consequent mega-tsunami - now exist on the island of La Palma
in the Canaries. In 1949 the southern volcano on the island erupted. During the
eruption an enormous crack appeared across one side of the volcano, as the western
half slipped a few metres towards the Atlantic before stopping in its tracks.
Although the volcano presents no danger while it is quiescent, scientists believe
the western flank will give way completely during some future eruption on the
summit of the volcano. In other words, any time in the next few thousand years
a huge section of southern La Palma, weighing 500 thousand million tonnes, will
fall into the Atlantic ocean.
What will happen when the volcano on La
Palma collapses? Scientists predict that it will generate a wave that will be
almost inconceivably destructive, far bigger than anything ever witnessed in modern
times. It will surge across the entire Atlantic in a matter of hours, engulfing
the whole US east coast, sweeping away everything in its path up to 20km inland.
Boston would be hit first, followed by New York, then all the way down the coast
to Miami and the Caribbean.