What is a tsunami (pronounced soo-nah-mee)? A tsunami is a series of waves that are generated in the ocean by a sudden disturbance that vertically relocates the water column. The word tsunami is a Japanese word meaning “harbor wave.” Tsunamis have sometimes been referred to as “tidal waves,” which they are not. The tidal level is a factor in the impact that a tsunami has on a coastline. However, they are unrelated to the tide.

Another name commonly used for tsunamis is “seismic sea wave.” This can be misleading. Some tsunamis are generated from an earthquake out at sea, which would cause seismic sea waves. However, tsunamis can also be generated by undersea landslides, meteorite impact, explosions and volcanic eruptions.

What does a tsunami look like? Picture what happens when you throw a stone into a pond. It creates a series of ripples. This is what a tsunami looks like, except on a much larger scale. The waves that form can travel for thousands of miles and have enough impact to flatten a small town. The sizes of the waves are determined by the depth of the water. The wavelengths or width can be 60 to 120 miles long and travel at speeds of about 450 to 500 miles per hour.

As the tsunami approaches land, the waves slow down due to the shallow water; however, they increase in height to 50 feet or higher. Even though the waves have slowed down, they still have extraordinary energy due to the large volume of water affected.

Most tsunamis originate in the Pacific Ocean around a region of volcanoes and seismic activity that encircles a 24,000-mile area called the “Ring of Fire.” Several states and countries have been affected by tsunamis. In 1960, a tsunami was generated by an earthquake off the coast of Chile, killing 150 people in Japan. The tsunami traveled 10,000 miles in 22 hours.

Another tsunami struck Japan in 1999, with the waves ranging from 50 to 65 feet. One wave reached a height of 90 feet. Approximately 40 tsunamis have struck the Hawaiian Islands since 1819. Other states affected by tsunamis are California and Alaska. Other countries affected by them include the Philippines, Mexico, Puerto Rico, Papua-New Guinea, Indonesia, New Zealand, Peru and several other islands.

Tsunamis can take on different forms based upon the angles of the seafloor. One could be where the sea empties the harbors and looks withdrawn. Then the tsunami’s walls of water come toward the shore. Other tsunamis give no warning, and flood suddenly. Any way that a tsunami strikes is devastating. The walls of water flood the coast, collapse lighthouses, break trees like twigs and demolish homes. Many people have been killed in tsunamis. For example, in 1883, a volcano erupted in Indonesia, causing tsunamis. Approximately 36,000 people were killed, the majority of these deaths resulting from the tsunamis.

So, the next time you throw a rock in a pond and see the ripples, realize that you have just created your own mini-tsunami.