La Palma volcano: Rumours of feared mega-tsunami debunked by experts

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Watch: Cumbre Veja volcano erupts in Spain

The Canary Islands have seen their first volcanic eruption in 50 years – causing old fears about a possible "mega-tsunami" that could lash America to resurface.

Various misleading articles suggested the eruption in the Cumbre Vieja mountain range on La Palma island, which began on Sunday, could trigger a rockfall that would cause America to be hit with a huge tsunami.

Experts have stepped in to quash the fears, which are based on a 20-year-old scientific paper and documentary that have repeatedly been debunked. 

America’s National Tsunami Warning Center said: “There is NO tsunami danger for the U.S. East Coast at this time, following the eruption of Cumbre Vieja volcano, La Palma, Canary Islands.

"The National Tsunami Warning Center is monitoring this situation and based on all available data, including nearby water level observations, there is no tsunami hazard for the US East Coast."

Read more: Volcano erupts on Canary Island

The eruption has forced the evacuation of about 5,000 people and destroyed about 100 houses.

It began on Sunday, shooting lava hundreds of metres into the air, engulfing houses and forests, and sending molten rock towards the Atlantic Ocean.

Fears of a "mega-tsunami" were initially sparked in 2001 by Dr Simon Day and colleagues at University College London.

Dr Day suggested an eruption of Cumbre Vieja could dislodge a huge section of the island of La Palma. 

The paper suggested this could lead to a vast tsunami that would be 2,000 feet high at the point the rock entered the water, and still up to 150ft high when it reached America. 

EL PASO, SPAIN - SEPTEMBER 19: Mount Cumbre Vieja erupts in El Paso, spewing out columns of smoke, ash and lava as seen from Los Llanos de Aridane on the Canary island of La Palma on September 19, 2021. - The Cumbre Vieja volcano erupted on Spain's Canary Islands today spewing out lava, ash and a huge column of smoke after days of increased seismic activity, sparking evacuations of people living nearby, authorities said. Cumbre Vieja straddles a ridge in the south of La Palma island and has erupted twice in the 20th century, first in 1949 then again in 1971. (Photo by Andres Gutierrez/Anadolu Agency via Getty Images)
Columns of smoke, ash and lava, as seen from Los Llanos de Aridane on La Palma, Canary Islands. (Andres Gutierrez/Anadolu Agency via Getty Images)

When such fears reappeared in the wake of Sunday's eruption, experts stepped in to damp them down.

Writing on Facebook, Luis González de Vallejo, director of the Geological Risks Area of Instituto Volcanológico de Canarias (Involcan), wrote: ‘The recent volcanic reactivation in La Palma has once again sparked the debate on the stability of the west flank of the island and, in particular, the Volcanic Building of the Old Summit, a recurring issue for decades, raising concern in society."

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He continued: ‘For 20 years now, when some researchers will affirm the possibility that there could be a major collapse of the west side of the Old Summit and as a result of this the generation of a megatsunami, fear has been transmitted over such a catastrophic event.’

De Vallejo said the hypothesis of a massive collapse leading to a mega-tsunami has been "rebutted and discarded". 

He points out that the collapse of the "Old Summit" would require a vast and extremely unlikely combination of eruption and earthquake – or for the volcano to grow bigger. 

Mount Cumbre Vieja erupts in El Paso, spewing out columns of smoke, ash and lava as seen from Los Llanos de Aridane on the Canary island of La Palma on September 19, 2021. - The Cumbre Vieja volcano erupted on Spain's Canary Islands today spewing out lava, ash and a huge column of smoke after days of increased seismic activity, sparking evacuations of people living nearby, authorities said. Cumbre Vieja straddles a ridge in the south of La Palma island and has erupted twice in the 20th century, first in 1949 then again in 1971. (Photo by DESIREE MARTIN / AFP) (Photo by DESIREE MARTIN/AFP via Getty Images)
Columns of smoke, ash and lava as seen from Los Llanos de Aridane on La Palma, Canary Islands. (Desiree Martin/AFP via Getty Images)

De Vallejo said: ‘For the Old Summit's flank to meet conditions close to instability would have to occur simultaneously an exceptionally high-magnitude earthquake and a large-magnitude volcanic eruption, or for the current volcanic building to reach its natural growth at least a thousand meters more above the current maximum elevation. 

"To reach this height, more than 40.000 years would have to go by, referring to the average growth rate of the island over the last million years. 

"On the other hand, the probability of an eruption with a high explosive rate at the same time as a large earthquake is extremely remote, according to the geological record of such events on the island. 

"Therefore, Old Summit is stable, even under the effects of eruptions similar to those that occurred in the last tens of thousands of years."

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Even if a collapse did occur, scientists using different models predicted that any waves created would be much smaller. 

Undersea topography would reduce the size of the waves – although the Canary Islands could still see significant damage. 

In an article written in 2013, earth scientist Professor Dave Pettley pointed out that the supposed mega-tsunami would only be created if all the rock fell into the sea at once – which never happens. 

Pettley wrote: "Previous flank collapses have occurred as a series of distinct events rather than as a single coherent block. Each of these could have been able to generate a very large wave, and even a local tsunami.  

‘However, they would not have generated a mega-tsunami. There is no reason to believe that a future event will behave differently, so this scare should be consigned to the garbage can once and for all."

Smoke rises from cooling lava in the residential area of Los Campitos at Los Llanos de Aridane, on the Canary Island of La Palma on September 20, 2021. - A surge of  lava destroyed around 100 homes on Spain's Canary Islands a day after a volcano erupted, forcing 5,000 people to leave the area. The Cumbre Vieja erupted on Sunday, sending vast plumes of thick black smoke into the sky and belching molten lava that oozed down the mountainside on the island of La Palma. (Photo by DESIREE MARTIN / AFP) (Photo by DESIREE MARTIN/AFP via Getty Images)
Smoke rises from cooling lava in the residential area of Los Campitos, La Palma, Canary Islands. (Desiree Martin/AFP via Getty Images)
Smoke rises from cooling lava in the residential area of Los Campitos at Los Llanos de Aridane, on the Canary Island of La Palma on September 20, 2021. - A surge of  lava destroyed around 100 homes on Spain's Canary Islands a day after a volcano erupted, forcing 5,000 people to leave the area. The Cumbre Vieja erupted on Sunday, sending vast plumes of thick black smoke into the sky and belching molten lava that oozed down the mountainside on the island of La Palma. (Photo by DESIREE MARTIN / AFP) (Photo by DESIREE MARTIN/AFP via Getty Images)
A surge of lava destroyed around 100 homes a day after a volcano erupted on on La Palma, Canary Islands, forcing 5,000 people to leave the area. (Desiree Martin/AFP via Getty Images)

This week, volcanologist Nemesio Perez said there were unlikely to be fatalities as long as no one behaved recklessly.

La Palma had been on high alert after thousands of tremors were reported over a week in Cumbre Vieja, which belongs to a chain of volcanoes that last had a major eruption in 1971 and is one of the Canaries' most active volcanic regions.

One man was killed in 1971 as he took photographs near the lava flows. 

A submarine eruption occurred about 10 years ago close to the islands but caused little damage.

Watch: Lava destroys 100 homes after eruption in Canary Islands

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