I see the Western Press is already making an issue of why India etc governments do not have tsunami warning networks. I think they are looking in the wrong direction, and should be asking a slightly different question... Why aren't our Western governments planning for tsunamia warning networks?..
libertypost.org
Title: WARNING: US also faces tsunami threat
Source: news24.com
URL Source: news24.com
Published: Dec 27, 2004
Author: news24.com
Post Date: 2004-12-27 09:28:17 by thinking4me
23 Comments
US also faces tsunami threat 27/12/2004 08:16 - (SA)
Paris - Cities on the US East Coast and in the Caribbean could be wrecked by a tsunami unleashed by the collapse of a volcanic island in the eastern Atlantic, British scientists believe.
A massive chunk of La Palma, the most volcanically active island in the Canaries archipelago, is unstable, says Simon Day, of the Benfield Grieg Hazard Research Centre at University College London.
He calculates that its flank could collapse the next time the volcano, Cumbre Vieja, erupts.
If so, that would send a dome-shaped wall of water up to 100 metres high racing across the Atlantic at 800 kilometres per hour, hitting the western coast of Africa and southern coast of England within a few hours.
Some eight hours after the collapse, the US East Coast and Caribbean would bear the brunt.
Cities from Miami to New York would get swamped by waves up to 50 metres high, capable of surging up to 20 kilometres inland, according to Day's research.
Tsunamis are commonly caused by earthquakes that occur under or beneath the sea.
But around three decades ago, the theory was born that these gigantic waves can also be caused by collapsing islands. The evidence for this came from debris in the mid-Pacific believed to have been strewn from a titanic landslide in Hawaii.
'Could blow any time'
Day published his findings on Cumbre Vieja in 1999 after a two-year study into the volcano, which occupies the southern half of La Palma.
He identified dozens of volcanic vents formed by successive eruptions over the past 100 000 years and collected samples of lava to built up a detailed geological picture.
He found that the volcano's vents are laid out in the shape of a three-pointed "Mercedes star", whose western flank - a mass comprising some 500 billion tonnes of rock - is gradually becoming detached as volcanic activity forces magma to the surface.
The flank is very slowly falling into the sea, but a major eruption by Cumbre Vieja could cause it to fall with catastrophic effect.
The big question is when this might occur. Some geologists say the threat cannot be assessed accurately because of the way in which volcanic pressures build up in the volcano's porous rock.
"Eruptions of Cumbre Vieja occur at intervals of decades to a century or so, and there may be a number of eruptions before its collapse," Day said, in a follow-up study in 2001 that estimated the astonishing speed at which the tsunami could travel.
La Palma reaches 6 500 metres from the surrounding ocean floor and to a height of 2 426 metres above sea level.
The island has had seven known eruptions, the last of which was in 1971, at a location on the island's southern tip and well away from an unstable ridge at the summit which is Day's biggest fear.
In August this year, one of Day's colleagues, Bill McGuire, told a conference on global geophysical disasters that Cumbre Vieja could blow "any time" and warned that there was insufficient watch on the volcano.
Edited by Ilse Arendse
news24.com
AND Mega-tsunami: Questions and Answers
1. When will the volcano on La Palma collapse? The collapse of the western flank of the Cumbre Vieja volcano, on the southern half of La Palma, is not going to happen tomorrow or next week. Tourists should not cancel their holidays to the Canary Islands, or to the east coast of the United States or the Caribbean.
What scientists are predicting is that the collapse is likely to happen any time within the next few thousand years. Scientists also know that a collapse will not happen without any warning. They will be able to alert people to possible danger several weeks in advance.
2. How do scientists know? Scientists have discovered that La Palma will collapse at the time of some future volcanic eruption on the summit of the Cumbre Vieja volcano. Eruptions on the summit occur on average every 200 years or so. The last summit eruption was in 1949, so it may be many decades before the next summit eruption takes place.
Furthermore, the collapse will not necessarily happen during the next summit eruption. It may well take five, ten or more summit eruptions before the collapse occurs. But scientists simply do not know how many eruptions it will take.
3. What effects would the collapse have? The western flank of the Cumbre Vieja volcano would slide down westwards into the Atlantic ocean. There would be very strong earthquakes across La Palma while the flank was sliding. As the flank slid into the sea, it would create a very large wave called a mega-tsunami. This wave would move rapidly westwards.
Most of the energy of the wave would head straight out across the Atlantic towards the United States, Bahamas and the Caribbean, but a smaller wave or waves would head in other directions too. All these waves would get smaller as they cross the Atlantic. However scientists believe that they could still be as much as 50 metres high, for example, when they reach the east coast of the United States.
4. Is there anything we can do to stop the collapse from happening? Scientists say that although the risk of a collapse happening in the next few decades is small, when it does happen, it will cause great destruction, both on La Palma itself and wherever the mega-tsunami from La Palma strike land.
Although nothing can be done to stop a collapse, scientists point out there is a lot that can be done to prevent loss of life when a collapse does eventually happen. With suitable monitoring, warning and evacuation, people can be moved out of the areas at risk.
5. Is there a similar danger anywhere else in the world? La Palma is the island where the clearest warning signs of a coming collapse have been found. However there are dozens of large active volcanoes across the world’s oceans. Most of these have collapsed in the past, and most will collapse in the future. On each island, collapses only occur at intervals of 100,000 years or more.
Most of these islands have not been studied in as much detail as La Palma, but one exception is the big island of Hawaii in the Pacific Ocean. Here too there are some signs that it might collapse in the next few thousand years.
6. Should I be worried by mega-tsunami? As an individual, you have much more chance of being killed in a car accident than by a mega-tsunami. Mega-tsunami are very rare. However, it is important for governments to understand the potential risk, so that they can decide what hazard preparations, if any, are required. bbc.co.uk
AND Mega-tsunami: Wave of Destruction BBC Two 9.30pm 12 October 2000 Revisited: BBC Four 7pm 24 May 2003
En español / In Spanish
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.
bbc.co.uk |
