This ridge trends in an approximate north-south direction and covers the southern third of the island. It is lined by several volcanic craters. Location: .
It is considered that this process was driven by the pressure caused by the rising magma super-heating water trapped within the edifice of the volcano. It is unlikely that the trapped waters could vapourise due to being under considerable pressure. What is postulated is that the waters were heated to a point where they could not absorb further thermal energy in the available space. Continuing heating required the water to expand further and the only way it could do so was to move the flank of the volcano. This resulted in the two earthquakes that were reported as occurring during the eruption.
Proof that the water did not vapourise are the absence of phreatomagmatic explosions - steam escaping explosively from the ground is often a precursor of volcanic activity. Further evidence that vapourisation did not occur is that when the rift was visited the following day by Rubio Bonelli, he reported that the newly opened fissure "... Was not issuing fumes, vapour, steam, ashes, lava or other materials ..." In fact at no time during or afterwards was steam or phreatomagmatic activity reported. Thus reinforcing the claim that the waters trapped within the edifice never vapourised which they would do IF the pressure had fallen sufficiently to allow the super-heated water to flash into steam.
Day et al (1999) and Ward and Day (2001) hypothesize that during a future unascertained eruption, the western half of the Cumbre Vieja - approximately 500km3 (5 x 10 11 m3) with an estimated mass 1.5 x 1015 kg, will catastrophically fail in a massive gravitational landslide and enter the Atlantic Ocean generating a so called "mega-tsunami." The debris will continue to travel - as a debris flow, along the ocean floor. Computer modelling indicates that the resulting initial wave may attain a local amplitude (height) in excess of and an initial peak to peak height that approximates to , and travel at about (approximately the speed of a jet aircraft), inundating the African coast in about 1 hour, the southern coast of England in about 3.5 hours, and the eastern seaboard of North America in about 6 hours, by which time the initial wave would have subsided into a succession of smaller ones each about to high. These may surge to several hundred metres in height and several apart but retaining their original speed. The models of Day et al, and Ward and Day, suggest that it could inundate up to inland. This would greatly damage or destroy cities along the entire North American eastern seaboard. The physical damage would take tens if not hundreds years to repair and restore. The economies of the countries affected would likewise take several years to return to the pre-inundation levels.
Detailed geological mapping shows that the distribution and orientation of vents and feeder dykes within the volcano have shifted from a triple rift system (typical of most oceanic island volcanoes) to one consisting of a single north-south rift. It is claimed that this structural reorganization is a response to evolving stress patterns associated with the development of a possible detachment fault under the volcano's west flank. Siebert (1984) showed that such failures are due to the intrusion of parallel and sub-parallel dykes into a rift. Eventually the structure becomes unstable and catastrophic failure occurs. There is no evidence that the 1949 section of the rift extends in a north south direction or that there is a developing detachment plane. Research is ongoing.
There is controversy however, about the threat presented by Cumbre Vieja. Current indications are that recent landslides may have been gradual, and therefore may not generate tsunamis unless they increased in magnitude. Studies of possible local "mega-tsunami" in the Hawaiian Islands, draw distinctions between the tsunami wave periods caused by landslides and subduction-zone earthquakes, arguing that a similar collapse in Hawaii would not endanger Asian or North American coastlines.
Sonar surveys around many volcanic ocean islands including the Canary Islands, Hawaii, Reunion etc., have mapped debris flows on the seafloor. Many of these debris flows are about long and up to thick, contain mega-blocks mixed up with finer detritus.
Moore (1964) was the first geologist to interpret such features depicted on a United States Navy bathymetric chart. The chart showed two features that seemed to originate from the Hawaiian islands of Oahu and Molokai.
In recorded history, the Krakatau eruption generated devastating tsunami, yet the damage was local and did not propagate across long distances. This may have been due to the confining geography of the areas.
Approximately 3615 years ago, the volcano on Santorini exploded in a VEI estimated at 6. Research suggests that the eruption generated a tsunami which inundated Crete, possibly triggering the downfall of the Minoan civilization.
An earthquake and landslide in Crillon Inlet at the head of Lituya Bay, Alaska, on 9 July, 1958 generated a so called "mega-tsunami," with an initial amplitude (height) of ~, which stripped trees and soil from the opposite headland and inundated the entire bay, destroying three fishing boats anchored there and killing two people. Once the wave reached the open sea however, it rapidly dissipated.
Erupting Cumbre Vieja Volcano in W. Africa could set off mega-tsunami; submerge entire eastern seaboard of US
Sep 01, 2005; The first signs of trouble began around 8 a.m. the morning of Dec. 26, 2004 with the rumbling sound of a moderate earthquake off...