Imagine a towering wall of water—over 1,000 feet high—barreling across the ocean at hundreds of miles per hour. The ground trembles, the ocean recedes unnaturally, and in a matter of moments, everything along the coast is engulfed. This isn’t the plot of a disaster film. It’s a real scenario scientists warn could unfold in parts of the United States. And the clock may already be ticking.
What we’re talking about isn’t an ordinary tsunami. These are mega-tsunamis—a rare but terrifying type of natural disaster triggered not by tectonic shifts alone, but by colossal landslides or volcanic collapses. The resulting waves are exponentially more powerful than traditional tsunamis, capable of decimating entire regions in seconds.
So where could such destruction occur? According to new scientific analyses, three U.S. regions are especially at risk: Alaska, Hawaii, and the West Coast. Let’s examine what puts each region in the path of such potentially catastrophic waves—and whether your hometown could be in danger.
What Is a Mega-Tsunami?
Tsunamis are most commonly triggered by underwater earthquakes that suddenly displace water. But mega-tsunamis are an entirely different beast. They result from a massive amount of material—like millions of tons of rock—suddenly crashing into the sea. The force of this impact can create waves that initially rise to thousands of feet before speeding across the ocean at the pace of a commercial airliner.
One of the best-known examples from the ancient past was caused by a planetary impact. Scientists studying traces left from a mile-high wave caused by a prehistoric asteroid impact estimate it would have started at 2,000 feet in height near the point of impact, then surged across entire continents, flattening everything in its path.
In today’s world, a number of geologic factors can still produce such waves—just not from asteroids. These include:
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Massive landslides triggered by earthquakes or melting permafrost
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Volcanic eruptions leading to the collapse of unstable slopes
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Glacial detachments that cause enormous rock masses to plunge into fjords or open ocean
While rare, mega-tsunamis are not theoretical. They have occurred—and experts believe they will again.
The Alarming Case of Alaska: A Land on the Edge
Alaska is one of the most geologically active areas in the world. With hundreds of volcanoes, frequent earthquakes, and a rugged landscape rapidly being reshaped by melting glaciers, it’s a perfect storm for landslide-triggered mega-tsunamis.
In fact, Alaska is home to the largest wave ever recorded in human history.
In 1958, a massive landslide caused by an earthquake in Lituya Bay sent nearly 90 million tons of rock plummeting into the water. The result? A wave that soared to an unbelievable 1,719 feet high, stripping trees and soil from the mountainsides like a lawnmower.
Though Lituya Bay’s unique topography helped concentrate the energy of the wave into a narrow fjord, the example is a stark warning of Alaska’s potential to unleash more devastating waves.
As climate change accelerates glacial melt, scientists fear this type of scenario could occur again. Warmer temperatures loosen mountain slopes once stabilized by permafrost. Combined with increased seismic activity, Alaska’s future could hold another disaster of immense proportions.
Steve Masterman, Director of Alaska’s Division of Geological Surveys, confirmed that monitoring efforts are underway: “We’re actively tracking areas where slope movement is accelerating due to glacial retreat. The more the landscape melts and shifts, the higher the risk becomes.”
Hawaii’s Volcanic Legacy: A Hidden Underwater Threat
The Hawaiian Islands are known for their picturesque beaches and fiery volcanoes. But lurking beneath their tropical beauty is a hidden risk: the sudden collapse of volcanic mountainsides into the sea.
Hawaiian volcanoes grow through countless lava flows, which stack atop one another, often creating unstable slopes. These massive builds are prone to collapse—especially during periods of increased seismic or volcanic activity.
The most alarming historical clue? Evidence of enormous undersea landslides found around the Hawaiian archipelago. These landslides likely caused ancient mega-tsunamis that could have devastated parts of the islands. If one occurred today, it could send waves barreling across the Pacific.
Volcanoes like Mauna Loa and Kilauea, both located on Hawaii’s Big Island, are still active—and particularly hazardous. Kilauea, in fact, was erupting as recently as May 2024. The southeastern flank of the Big Island is especially concerning to geologists, as it’s slowly sliding toward the ocean. One day, a large portion could break off all at once.
Penn State University researchers have modeled the possible effects of such a collapse. Their simulations reveal waves that could reach over 1,000 feet near the origin, striking neighboring islands within minutes and racing across the Pacific to threaten the West Coast and even parts of Asia.
The West Coast’s Quieter Menace: Cascadia Subduction Zone
While the Hawaiian and Alaskan threats are dramatic and volcanic in nature, the West Coast of the U.S. faces its own silent killer: the Cascadia Subduction Zone.
Stretching from Northern California to British Columbia, this fault line is capable of producing magnitude 9.0+ earthquakes. It last ruptured in 1700, sending shockwaves across the ocean and triggering a tsunami that struck Japan without warning.
Closer to home, the indigenous village at Pachena Bay was obliterated. Oral histories from local communities describe waves as high as 100 feet swallowing the coast. No survivors were recorded.
Modern projections by the U.S. Geological Survey (USGS) and FEMA estimate there is a 37% chance of a magnitude 8.0–9.0 earthquake in Cascadia within the next 50 years. Should this happen, the tsunami could devastate parts of Washington, Oregon, and Northern California, leaving little time for evacuation.
Unlike mega-tsunamis caused by landslides or eruptions, a Cascadia event wouldn’t send waves thousands of feet tall. But it could still bring 50–100 foot waves capable of destroying towns and infrastructure along the coast.
Are We Ready? How the U.S. Is Preparing for the Next Big Wave
The terrifying nature of mega-tsunamis makes them particularly difficult to prepare for. Their rarity means communities aren’t used to dealing with them, and their magnitude makes traditional defense measures almost useless.
Still, steps are being taken:
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Monitoring Systems: In Alaska, Hawaii, and the Pacific Northwest, sensors and satellite imagery are used to detect slope movement, seismic activity, and early signs of volcanic collapse.
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Emergency Planning: FEMA has worked with local governments to create evacuation routes, siren systems, and public awareness campaigns—especially in coastal towns most at risk.
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Research Investment: Institutions like NOAA and the USGS are investing in better tsunami modeling and simulation technology. This allows for improved forecasting of wave heights, timing, and impact zones.
But preparation only goes so far. Mega-tsunamis move fast. In many scenarios, there might be less than 30 minutes between the triggering event and the wave making landfall. That leaves little time for even the best-laid plans.
Could Your Hometown Be at Risk?
If you live anywhere near the coasts of Alaska, Hawaii, or the Pacific Northwest, it’s worth learning your community’s tsunami evacuation routes. Even areas not directly on the coast could be affected by flooding, road closures, and infrastructure damage.
While cities like Anchorage, Honolulu, Seattle, and San Francisco are obvious areas of concern, smaller communities and tourist destinations along the coast may face even greater risk due to limited infrastructure and fewer escape routes.
If you’re unsure whether your hometown is in a tsunami risk zone, consult NOAA’s Tsunami Hazard Maps or check with your local emergency management office.
What to Do During a Tsunami Warning
Here are a few quick tips to follow if a tsunami warning is issued in your area:
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Move to Higher Ground: Don’t wait. As soon as a warning is issued, get to higher elevations or inland.
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Stay Informed: Listen to emergency broadcasts via NOAA weather radio, local news, or government alerts.
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Know Your Routes: If you live in a tsunami hazard zone, know how to get out—preferably without relying on bridges, which may collapse.
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Have a Go-Bag: Emergency kits with food, water, medical supplies, and communication tools are essential.
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Practice Evacuations: Families should rehearse what to do if a tsunami strikes while at home, work, or school.
Final Thoughts: The Calm Before the Wave?
Mega-tsunamis are rare—but history shows they are not myths. Scientists have uncovered plenty of evidence proving their devastating potential, and current geological changes mean the risks are real and growing.
From the icy cliffs of Alaska to the volcanic shores of Hawaii and the trembling seabed off the West Coast, the United States faces natural forces more powerful than almost any human structure can withstand.
The best way to protect ourselves? Stay informed, stay prepared, and never underestimate the power of nature when it decides to unleash a wave unlike anything we’ve ever seen.
