Scientists are raising the alarm over the potential for a catastrophic “mega-tsunami” that could strike three major areas across the United States.

Researchers from Virginia Tech have warned that an enormous earthquake—measuring 8.0 on the Richter scale—could hit the U.S. for the first time in over 300 years.

The resulting tsunami could unleash waves as high as 1,000 feet, capable of wiping out entire communities and making the affected regions unlivable.

The findings were published last month in the Proceedings of the National Academy of Sciences, detailing the serious threat posed by the Cascadia Subduction Zone, a 600-mile fault line stretching from northern California to southern British Columbia.

According to the research, the three areas most at risk are Alaska, Hawaii, and the U.S. West Coast. New warnings have only recently been issued for parts of the mainland.

Alaska is already known to be vulnerable due to its unstable terrain and frequent seismic activity, now worsened by climate change, which is accelerating glacial melt and further weakening the land.

Hawaii, with its volcanic origins, has a long history of devastating tsunamis triggered by volcanic collapses, sending massive volumes of rock into the sea.

The U.S. West Coast—part of the seismically active Pacific Ring of Fire—is also in serious danger.

This region is responsible for some of the world’s most powerful earthquakes, volcanic eruptions, and tsunamis.

The study warns that the perfect storm of a powerful quake and rising sea levels could result in a mega-tsunami impacting areas such as northern California, northern Oregon, and southern Washington.

Researchers estimate there’s a 15% chance of a quake larger than 8.0 hitting this region within the next 50 years.

Such an event could cause land along the coast to sink by as much as 6.5 feet, dramatically increasing the size of the coastal floodplain.

Lead author Tina Dura, an assistant professor of geosciences at Virginia Tech, emphasized that the expansion of the floodplain from such a quake had not been previously measured.

She warned this could seriously delay recovery efforts and potentially render entire communities uninhabitable.

If the earthquake occurred today, Dura’s team estimates it would affect approximately 14,350 people, damage 22,500 buildings, and flood 777 miles of roads.

By the year 2100, with sea levels expected to rise by three more feet, the potential for damage will be even greater.

“In the future, as sea levels continue to rise, the land subsidence caused by a major earthquake will delay recovery even more due to critical infrastructure being compromised,” Dura explained. “In the long term, some coastal communities may no longer be viable places to live.”

Although the last major quake in the Cascadia region occurred in January 1700 and the area isn’t densely populated, Dura stressed that many communities sit directly in the danger zone.

“In these areas, the effects of land subsidence could be more severe than what we’ve seen in similar large-scale quakes globally,” she said.