Tsunamis are also caused by nearshore or underwater landslides, or volcanic eruptions. This differs from regular ocean waves that are generated from the wind. Often the first wave of a tsunami may not be the largest. The danger from a tsunami can last for several hours after the arrival of the first wave. Sometimes a tsunami causes the water near the shore to recede, exposing the ocean floor.
Tsunami can be very large.
Tsunami can travel up rivers and streams that lead to the ocean.