Imagine hundreds of miles per hour as a wall of water, up to a third of a mile high, roars across the ocean. It is nearly impossible to comprehend the magnitude of a mega-tsunami’s destructive power.

Mega-tsunamis, as opposed to ordinary tsunamis brought on by earthquakes, are frequently brought on by massive landslides or erupting volcanoes.

Because of their closeness to landslide-prone areas, earthquake zones, and unstable volcanoes, three US regions—Alaska, Hawaii, and the West Coast—are at risk of mega-tsunamis.

Scientists continue to analyse the traces left by a mile-high mega-tsunami that was caused by an asteroid strike millions of years ago during the dinosaur era.

The Cumbre Vieja volcano on the Canary Island of La Palma is one terrifying possibility that might collapse into the Atlantic today and unleash a mega-tsunami towards the US East Coast.

The Netflix series ‘La Palma’ vividly depicts this situation, with a family on vacation while scientists find evidence of a volcanic explosion that can cause a devastating tsunami.

This concept originates from a 2001 study by Dr. Simon Day and Steven Ward, who cautioned that a collapse of the west flank of Cumbre Vieja may cause a huge wave to form by dropping up to 120 cubic miles of rock into the sea.

According to their analysis, this wave might harm coastal communities by starting at 2,000 feet high close to the volcano and reaching up to 150 feet when it strikes the Americas.

The US has much greater imminent mega-tsunami dangers in three areas: Alaska, Hawaii, and along the West Coast. However, other experts say that this Cumbre Vieja scenario is implausible because the volcano has erupted without producing such a tsunami.

These regions have already seen destructive waves brought on by earthquakes, landslides, or volcanic collapses—processes that are comparable to those examined in the Canary Islands.

Millions of people and coastal communities are at risk from future mega-tsunamis due to ongoing geological activity and environmental changes.

Alaska

Millions of tonnes of rock crashed into Gilbert Inlet in 1958 as a result of a catastrophic landslip caused by an earthquake near Alaska’s Lituya Bay.

It is estimated that the massive granite mass, which measured roughly 2,400 feet by 3,000 feet, weighed up to 90 million tonnes. According to NASA, that was the same as dumping eight million dump truck loads into the ocean.

The outcome was a 1,719-foot mega-tsunami that swept across the bay, the biggest wave ever recorded.

A ‘razor-cut’ line was observed by explorers as early as 1786, and witnesses described a loud ‘boom’ as ice-filled waves washed away lighthouses and stripped forests bare.

Another pair was never seen again, and one fisherman’s boat was raised so high he could see treetops below.

Similar to the Cumbre Vieja situation, a landslip caused the mega-tsunami at Lituya Bay. Massive volumes of rock can be shaken loose from sheer cliffs by earthquakes in this area, which can also displace water and produce huge waves.

The wave was particularly devastating because of the bay’s limited waters, which increased its height.

Alaska is still a landslip hotspot due to its untamed landscape and regular earthquakes.

Because melting glaciers destabilise slopes and loosen bedrock, climate change is making the problem worse.

Fourteen experts issued a warning in 2020 that a rockslide into Harriman Fiord could result from Barry Glacier’s retreat, which could cause a huge wave the size of Lituya Bay.

The director of Alaska’s Division of Geological Surveys, Steve Masterman, stressed that as temperatures rise, the likelihood of these occurrences increases. In order to forecast and get ready for future calamities, scientists are currently keeping an eye on slopes and glaciers.

Hawaii

Mega-tsunamis caused by collapsed volcanoes have a history of occurring on Hawaii’s volcanic islands. Marine fossils were left high on the slopes of the island of Lanai after a 1,000-foot tsunami crashed onto it some 105,000 years ago.

Similar to the Cumbre Vieja scenario, researchers think this was created by a major volcanic landslip.

The coasts of the islands were changed by the massive amounts of rock that were hurled into the sea by other historic slides, including as the 20-mile-long Nu’uanu slide, which created waves as high as 300 feet.

Layers of lava are piled up by Hawaii’s volcanoes to build, but these slopes can become unstable and fall, particularly during earthquakes or eruptions.

Millions of tonnes of rock may tumble into the ocean as a result, causing mega-tsunamis that destroy neighbouring islands. These incidents are especially deadly because of the steep terrain of the islands.

Volcanoes in Hawaii are still active, and the biggest hazard is found on the southeast part of the Big Island, which is home to “younger” volcanoes like Kilauea and Mauna Loa.

Kilauea has actually been erupting lava for months. On May 6, the most recent eruption in its current cycle came to a close.

Researchers from Penn State caution that these precarious slopes might collapse once more, causing enormous waves.

The islands remain vulnerable to tsunamis because to the continuous volcanic activity and regular earthquakes.

Residents and tourists must be prepared for unexpected tsunami alerts and evacuation orders, even as scientists keep an eye on landslide-prone areas and volcanic activity.

The West Coast

The West Coast settlement of Pachena Bay was destroyed on January 26, 1700, when a magnitude 9 earthquake along the Cascadia Subduction Zone triggered a mega-tsunami.

Only 30 minutes after the earthquake, waves as high as 100 feet hit, leaving no survivors.

Huu-ay-aht Speaking in 1964, Chief Louis Clamhouse related the oral narrative, saying, “The land shook at night.” There was no time for them to flee. Everyone drowned.

Additionally, coastal woods were dropped into the tidal zone by the earthquake, resulting in “ghost forests” of dead tree stumps that are still evident today. Japan recorded an enigmatic tsunami across the Pacific that was subsequently connected to this incident.

A large seismic event, in which one tectonic plate moves beneath another, was the cause of the Cascadia mega-tsunami, as opposed to landslide-driven tsunamis.

Massive volumes of ocean water are displaced by this movement, causing tsunamis to travel great distances. The 1700 incident demonstrated the potential reach of these waves.

One of North America’s most active seismic zones, the Cascadia Subduction Zone is likely to see another significant earthquake in the ensuing decades.

A tsunami like the Tohoku-oki tragedy in Japan in 2011, which claimed around 16,000 lives, might be triggered by a similar incident.

According to estimates from the US Geological Survey and FEMA, the likelihood of an earthquake in Cascadia with a magnitude of 8 to 9 occurring over the next 50 years is 37 percent.

Parts of the shoreline may permanently sink, submerging coastal cities like Tillamook, Astoria, and Newport.

Although early warning systems and evacuation plans are being improved by researchers, the tsunami hazard persists due to the region’s earthquake susceptibility.

Because of their dynamic geology and shifting surroundings, Alaska, Hawaii, and the West Coast are constantly at risk of mega-tsunamis.

As in the past, landslides driven by melting glaciers in Alaska, shaky volcanoes in Hawaii, and strong earthquakes around the West Coast could cause devastating waves.

The hazard persists even as communities plan and educate themselves, and scientists keep an eye on these threats.