http://en.wikipedia.org/wiki/Megatsunami
Americas East Coast Megatsunami Canary Islands Geologists S. Day and S. Ward consider that a megatsunami could be generated during a future eruption involving the Cumbre Vieja on the volcanic ocean island of La Palma, in the Canary Islands.[12][13]
In 1949, the Cumbre Vieja volcano erupted at its Duraznero, Hoyo Negro and San Juan vents. During this eruption, an earthquake with an epicentre near the village of Jedy occurred. The following day Rubio Bonelli, a local geologist, visited the summit area and discovered that a fissure about 2.5 km long had opened on the eastern side of the summit. As a result, the western half of the Cumbre Vieja (which is the volcanically active arm of a triple-armed rift) had slipped about 2 m downwards and 1 m westwards towards the Atlantic Ocean[citation needed].
The Cumbre Vieja volcano is currently in a dormant stage, but will almost certainly erupt again in the future. Day and Ward hypothesize[12][13] that if such an eruption causes the western flank to fail, a megatsunami will be generated.
La Palma is currently the most volcanically active island in the Canary Islands Archipelago. It is likely that several eruptions would be required before failure would occur on Cumbre Vieja.[12][13] However, the western half of the volcano has an approximate volume of 500 km3 (5 x 1011 m3) and an estimated mass of 1.5 x 1015 kg. If it were to catastrophically slide into the ocean, it could generate a wave with an initial height of about 1,000 metres (3,281 ft) at the island, and a likely height of around 50 metres (164 ft) at the Caribbean and the Eastern North American seaboard when it runs ashore eight or more hours later. Tens of millions of lives would be lost as New York, Boston, Baltimore, Washington D.C., Miami, Havana, and many other cities near the Atlantic coast are leveled. The likelihood of this happening is a matter of vigorous debate.[14]
The last Cumbre Vieja eruption occurred in 1971 at the southern end of the sub-aerial section without any movement. The section affected by the 1949 eruption is currently stationary and does not appear to have moved since the initial rupture.[15]
Geologists and volcanologists also disagree about whether an eruption on the Cumbre Vieja would cause a single large gravitational landslide or a series of smaller landslides.
