Definition: 

Tsunamis are formed by sudden disturbances in or near a body of water, most commonly underwater earthquakes, volcanic eruptions, landslides, or meteorite impacts, which displace large volumes of water and generate powerful waves.

Explanation: 

Tsunamis typically form when there’s a rapid and significant displacement of water in the ocean. The most common cause is an underwater earthquake, where tectonic plates shift, causing the seafloor to rise or fall suddenly. This movement pushes or pulls the water above, creating waves that spread outward. Other causes include volcanic eruptions (which can displace water or cause underwater landslides), coastal or underwater landslides, or even rare events like meteorite impacts. These waves travel across the ocean at high speeds (up to 500-600 mph in deep water) and grow in height as they approach shallower coastal areas, leading to destructive flooding. The energy of a tsunami can travel thousands of miles, making it a far-reaching hazard.

Example: 

Imagine an underwater earthquake near Japan shakes the ocean floor. This movement pushes a huge amount of water upward, like dropping a stone in a pond. The displaced water forms waves that spread across the Pacific Ocean and may hit distant shores, like the west coast of the U.S., as a tsunami.