In an episode of the
BBC Horizon series broadcast on 12 October 2000, two geologists hypothesised that during a future eruption, the western flank of
Cumbre Vieja, with a mass of approximately 1.5 ×1015 kg, could slide into the ocean. This could then generate a giant wave, known as a "
megatsunami" around high. The wave could radiate out across the Atlantic and inundate much of the eastern seaboard of North America, and many of the islands in the
Caribbean and northern coasts of South America between six and eight hours later. They estimate that such a tsunami could have waves possibly or higher causing massive devastation along the coastlines. Modelling suggests that the tsunami could inundate up to inland. The claim was also explored in a BBC docu-drama called
End Day which went through several hypothetical scenarios of disastrous proportions. However, nowhere in their papers do the authors make any claim about the imminent collapse of the flank. Rather, they state that they have modelled the worst-case scenario. In 2002 the Tsunami Society published a statement stating "... We would like to halt the scaremongering from these unfounded reports..." The major points raised in this report include: • The claim that half of Cumbre Vieja dropped during the 1949 eruption is erroneous, and contradicted by physical evidence. • No evidence was sought or shown that there is a fault line dividing the island of La Palma. • Physical evidence shows a long line in the rock, but the models assumed a line, for which no physical evidence was given. Further, there is no evidence shown that the long line extends to beneath the surface. • There has never been a megatsunami in the Atlantic Ocean in recorded history. A geological survey published in 1999 concluded that the western flank is stable with no evidence of
aseismic creep. Other experts agree that the
fracture resulting from the 1949 eruption is a shallow and inactive surface expression that should be monitored, but consider the possibility that it is unstable as being almost nonexistent. Also, it is likely that the
morphology of the floor of the Atlantic Ocean would hinder the propagation of a transoceanic tsunami. In 2006 Jan Nieuwenhuis of
Delft University of Technology simulated several volcanic eruptions and calculated it would take another 10,000 years for the flanks to become sufficiently high and unstable to cause a massive collapse. A 2008 paper looked into the worst-case scenario of a massive landslide and subsequent megatsunami. The authors concluded that waves could reach heights in the range 10 to 188 meters in the Canary Islands, but that the waves would dissipate as they radiated out into the Atlantic Ocean. They predict 40 meters height for some nearby island systems. For continents, the worst effects would be expected in Northern Brazil (13.6 m), French Guiana (12.7 m), mid-US (9.6 m), Western Sahara (largest prediction at 37 meters) and Mauritania (9.7 m). While still large, this would not qualify as a megatsunami (apart from locally in
Macaronesia), with the highest prediction for Western Sahara comparable to the
2011 Japanese tsunami. ==Climate==