What exactly is a tsunami? Understanding the formation and movement of these devastating ocean monsters

A tsunami isn’t just a larger version of beach waves—it’s an event that moves the entire ocean column. Unlike wind-driven waves that affect only the top few feet, a tsunami forms when something displaces the seafloor up or down, lifting the water above it and pushing a broad surge outward. Most tsunamis are linked to large, shallow earthquakes that rupture and shift the seabed vertically; for example, the May 19, 2023 magnitude 7.7 quake southeast of the Loyalty Islands involved about 5.6 feet (1.7 m) of slip. Scientists also study landslides in flume tests, showing rougher slide material can damp waves faster.