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24 September 2014
Science & Nature: TV & Radio Follow-upScience & Nature
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Mega-tsunami: Questions and Answers

Mega-tsunami1. 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.

Mega-tsunami: Wave of Destruction programme page

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