A tsunami is a huge and powerful ocean wave.
It’s sometimes called a tidal wave, but they have nothing to do with the tides. A tsunami is caused by a sudden movement of huge amounts of ocean water from below.
Sometimes, a tsunami is only a foot high, but it can be as long as 60 miles!!!! And it can travel across the top of the ocean at up to 500 miles per hour.
Once the tsunami reaches the coastline, the wave can quickly get higher, sometimes up to 50 to 100 feet high!
The wave then crashes onto the coast and floods the land.
The water can reach 1000 feet inland and can be strong enough to destroy homes.
Most happen in the Pacific Ocean but they can happen in the Atlantic too and they usually happen when an undersea volcano erupts.