Cumbre Vieja (Spanish: "Old Summit") is a volcanic ridge on the island of La Palma in Spain's Canary Islands.
Volcanic history
La Palma is not only the steepest island in the world but has also been the most volcanically active of the Canary Isles in the past 500 years. The last three eruptions in the ridge were in 1470, 1585, 1646, 1677, 1712, 1949, and 1971.
1949 eruption
During the 1949 eruption the western half of the Cumbre Vieja ridge slipped several metres downwards into the Atlantic Ocean. This also opened a two-kilometre-long fracture which can quite easily be seen to this day. It is believed that this process was driven by the pressure caused by the rising magma heating and vaporising water trapped within the structure of the island.
Future threat
Scientists warn that in some future eruption within the next few thousand years the western half of the island, approximately 500km3 of land weighing an estimated 500 billion tonnes, will slide into the ocean -- a so called "lateral collapse". Should that happen, the resulting megatsunami would reach heights of 100 metres and the speed of a jetliner, reaching the African coast in three hours, the coast of England in five, and the eastern seaboard of North America in twelve. This could destroy cities along the United States' east coast, such as New York, Boston, Washington, DC, Norfolk, Virginia, and Miami, and penetrate as far as 25 km inland, devastating whole regions. It is observed that, over the last several thousand years, the distribution and orientation of vents and feeder dykes within the mountain have shifted from a triple rift system (typical of most oceanic island volcanoes) to one consisting of a single N-S rift with westward extending vent arrays. Some argue that these structural re-organizations are in response to evolving stress patterns associated with the growth of a detachment fault under the volcano's west flank.[1]
There is controversy about the seriousness of the threat, with indications that usually the landslides there are gradual, thus not likely to generate tsunamis. There is no record of a megatsunami ever being caused by a massive landslide, but scientists have now identified the island of La Palma as a potential hazard. Although, history has documented large and damaging tsunamis from far smaller lateral collapses of stratovolcanoes and residual debris found on the seafloor does provide evidence of their abundance in recent geological time (see Storegga Slide).
As of 2004, very little seismological monitoring of Cumbre Vieja is being carried out.
External links
Information and sources
- Benfield Hazard Research Center: Why the only certainly about the La Palma tsunami is that it will happen
- Benfield HRC Q&A
- Pdf giving details