The Canary Islands Seismic Network registered at 10:48 pm local time / 5:48 pm ET an earthquake having a magnitude of 4.9 located 17 miles deep in La Palma where the La Cumbre Vieja Volcano continues to have a significant, ongoing eruption which continues to send a river of lava into the Atlantic Ocean. This earthquake is one of dozens that have struck the erupting island, suggesting more explosive volcanic activity is likely to rock the Canary Island hotspot. While lava is pouring into the ocean, covering communities and banana plantations as it travels from the erupting fissures to the coast, and earthquakes of varying magnitudes continue to hit the area, there is no threat of a local tsunami nor is there any threat of a tsunami along the East Coast of the United States and Canada at this time.
The La Cumbre Vieja Volcano sprung to life on September 19, erupting lava for the first time since 1971. The eruption has been the largest in modern times there ; more than 10,000 residents have been evacuated while lava has consumed thousands of buildings.
— the Weatherboy (@theWeatherboy) October 16, 2021
A study published in 1999 suggested that La Cumbre Vieja could be in the initial stages of failure, in which the volcano could collapse in on itself. A 2000 BBC television program, “Mega-tsunami: Wave of Destruction” expanded on the theory, suggesting that the failure and collapse of the western flank of the volcanic island is possible which in turn would send a destructive mega-tsunami to the U.S. East Coast. A follow-up program in 2013 on BBC, called “Could We Survive the Mega-Tsunami?” continued to paint the possibility of a volcano collapse and massive tsunami as a result of that collapse throughout the Atlantic Ocean.
— the Weatherboy (@theWeatherboy) October 20, 2021
A “mega tsunami” is an extremely large wave created by a large, sudden displacement of material into a body of water. While typical tsunamis are created by underwater earthquake activity in which a sea floor rise or fall occurs and displaces that water, a mega tsunami is caused when a massive amount of material suddenly falls into the water; this could be created by large meteor impact or by a major landslide, especially of volcanic islands. While a regular tsunami could be as high as 100 feet tall from a powerful earthquake, a mega tsunami could rise hundreds to even thousands of feet high. Because a mega tsunami is so huge, it would be able to travel dozens of miles inland or more very quickly.
In 2001, Steven N. Ward and Simon Day proposed in a research article that a change in the eruptive activity of the volcano erupting today and a fracture on the volcano that formed during an eruption in 1949 may be the prelude to a giant collapse. They estimated that such a collapse could cause tsunamis across the entire North Atlantic Ocean and severely impact the United States and Canada. However, subsequent research has debated whether the tsunami would still have a significant size far away from La Palma, as the tsunami wave may quickly decay in height away from the source and interactions with the continental shelves could further reduce its size. Some evidence indicates that most collapses in the Canary Islands took place as multistage events that are not as effective at creating tsunamis, and a multi-stage collapse at La Palma likewise would result in smaller tsunamis.
In the United States, USGS has been adamant in getting the word out that a mega-tsunami is unlikely. After the volcano started to erupt at La Palma, USGS Tweeted, “Collapses have happened in the Canary Islands, but they are very very rare, and the tsunami threat is local. The ‘mega tsunami’ story for the whole Atlantic has been thoroughly debunked.” USGS continues to assert that position, pointing to an article on the American Geophysical Union website that debunks the idea that volcanic activity on the Canary Islands would trigger a tsunami. That article calls the tsunami theory “an absolutely extreme scenario based on a very highly unlikely combination of events that is without precedent.”
While the collapse of La Palma seems unlikely, earthquake and volcano hazards are very real and continue. The island, home to 85,000, continues to be at risk for more and potentially stronger earthquakes and even more active fissures and lava flows.
— the Weatherboy (@theWeatherboy) September 19, 2021