What makes a tsunami — and what to do if one comes

A traffic police officer in Peru sets up a roadblock during a tsunami warning in La Punta, Callao province on July 30, 2025. Alerts were issued in countries across the Pacific, following a massive 8.8-magnitude earthquake off the east coast of Russia.

Several factors help determine whether a given earthquake will generate a dangerous tsunami, but the process is not yet fully understood.

(Image credit: Connie France)