Megatsunami threatens these three US states. Waves could reach as high as 1000ft, reveals study

A warning has been issued for America, according to a recent study from Virginia Tech, published in the Proceedings of the National Academy of Sciences, with three states—Washington, Alaska, and Hawaii—most likely to experience megatsunamis within the next five decades.

The enormous waves, much stronger than usual tsunamis, can reach heights of up to 1,000 feet, threatening coastal towns and buildings.

What are megatsunamis?

Megatsunamis are vastly different from typical tsunamis. While the latter are primarily induced by earthquakes under the sea and typically generate waves of about 30 feet high, megatsunamis may be caused by landslides, volcanic eruptions, or glacial movements and have much greater displacement of water and destructive effects.

There was a megatsunami in Lituya Bay in Alaska in October 1936 with a run-up height of up to 150 metres (490 ft) at the maximum height in Crillon Inlet at the head of the bay.

The four witnesses of the wave in Lituya Bay itself all survived and recounted it as having been between 30 and 76 metres (100 and 250 ft) high.

The major hazard in Washington arises from the Cascadia Subduction Zone, a geological fault that extends from Northern California to British Columbia. Scientists believe there's at least a 15% chance of a magnitude 8 or higher earthquake striking the region within the next five decades. If that happens, the resulting land subsidence—up to 6.5 feet in some places—could drastically expand the coastal flood zone. Such a quake would likely generate massive waves capable of overwhelming entire coastal towns and cities.

Alaska is doubly at risk. Sitting on the seismically active Pacific Ring of Fire, it is vulnerable to huge earthquakes, especially along the Aleutian Islands. But it is also exposed to a lesser-known risk from global warming. As glaciers melt at a rapidly rising rate, slopes previously stabilised by ice give way, increasing the risk of huge landslides into the sea. These uncontrolled collapses may generate waves powerful enough to devastate coastal communities far beyond Alaska itself.

Hawaii's volcanic terrain is a threat of a different kind. Landslides across entire areas from volcanic flank collapse—when the flank of a volcano collapses and slides into the ocean—have the potential to release massive waves. Such incidents have happened in the past, according to history, and researchers say they may happen again.

The study stresses a need for readiness, and with the uncertain and possibly abrupt onset of these disasters, expenditure on early warning systems, evacuation preparedness, and public education campaigns is imperative. Risks and procedures need to be taught to communities, particularly those living in low-lying coastal areas.

Experts also point to the increasing contribution of climate change in enhancing natural disasters. Global warming and rising seas may make tsunami impacts more destructive, extending the area and force of incoming waves. This convergence of seismic activity and environmental change makes longer-term planning and resilience more critical than ever.