What Is the Difference Between a Tsunami and a Tidal Wave?

Tidal waves are shallow water waves caused by the gravitational interactions from the sun, moon and Earth, and tsunamis are large ocean waves triggered by volcanic eruptions, landslides and large earthquakes under the ocean floor. Tsunamis actually have nothing to do with the tides in the oceans.

The moon's gravitational pull causes the ocean to bulge on the side facing it. Inertia causes the ocean to also bulge on the opposite side facing the moon. The process of the ocean bulging as a result of these forces creates lunar tides. Most locations on Earth experience two high tides and two low tides every 24 hours.

A tsunami is a series of waves that sends surges of water onto land. Tsunamis are most often caused by large undersea earthquakes that occur at tectonic plate boundaries. When the ocean floor rises or drops suddenly due to an earthquake, it displaces the water above it, causing a series of rolling waves to travel across the sea at speeds up to 500 mph. As the waves reach the shore, they enter shallower water. The waves slow down, but the tops of the waves move faster than their bottoms do, which causes them to rise significantly in height.