Part 1: General Information

Anna Tinoco
What is a tsunami?

A tsunami is a series of large waves produced by an underwater earthquake, volcanic eruption, or landslide.

How do tsunamis form?

Tsunamis form when there is a sudden movement in tectonic plates caused by the plates moving over, along, or away from each other. This causes a disturbance that vertically displaces the water column above it. This sends large waves out in all directions. Tsunamis are usually caused by earthquakes that are greater than 6.5 on the Richter scale and are less than 30 miles below the surface of the water.

How often do tsunamis occur and how long do we have to react?

Tsunamis occur irregularly and it is hard to predict when they will occur. Off shore earthquakes are the most common cause of tsunamis so when an earthquake occurs, tsunamis can be expected. Tsunamis are generated very rapidly and can reach the shore very quickly. If a tsunami warning is issued, it is wise to move to high ground immediately. If you are on the beach and you notice changes in sea level, ground shaking on the shore, or loud roaring coming from the water, there may be a tsunami coming. These are all natural signs of tsunamis. At the first sign or warning of a tsunami, you can have anywhere from a few seconds to a few hours to move away from the water. It is very hard to predict the arrival time of a tsunami so moving to high ground immediately is advised.

How large of an area is affected by a tsunami?

Tsunamis are usually between 12 miles and 30 miles wide by the time they reach the shore. They can last anywhere from 5 minutes to an hour. Tsunamis are usually around 3 feet tall when they are first formed in deep waters so they often go unnoticed when they are first formed. This is why they are so hard to predict. However, tsunamis grow in height as they approach shallow waters. By the time they reach the shore, they can be about 100 feet tall. The waves can travel at speeds up to 400 mph and typically slow down when they reach shallower waters. Once they waves reach the shore, they can travel hundreds of feet inland.

What risks are associated with tsunamis?

The giant waves produced by tsunamis can travel hundreds of feet inland, bring boat, rocks, and other debris from the ocean with it. This debris can crush property and people that are near the shore. The large waves also destroy buildings and carry people, cars, and other debris back out to sea. Tsunamis can cause severe damage to people and property near the shore.