(Describer) Under a round logo of a wave, title: Ocean Today.

[dramatic music plays]

(Describer) The red and white flag of Japan fills the screen, then slides away to reveal Japan's islands. Titles: Tsunami Strike - Japan. Part 1: Destruction.

(Describer) A huge wave is viewed from above.

(male narrator) On March 11, 2011, a 9.0 magnitude earthquake off the Pacific coast of Japan generated a tsunami. This series of ocean waves sped towards the island nation with waves reaching 24 feet high. The result was devastation and utter destruction.

(Describer) Flooding carries buildings into other buildings.

Towns were engulfed by water and swept away. Farmland was flooded. Tens of thousands of lives were lost. The National Police Agency reported damages to hundreds of roads, bridges, and more than 100,000 buildings.

(Describer) Water carries vans over a wall.

The surging water flooded rivers and destroyed harbors.

(Describer) A boat falls over and gets wedged under a bridge.

In some areas along the coast, tsunami waves reached six miles inland.

(Describer) It floods farmland.

Tsunamis not only cause severe damage when they first strike land, but also as the water recedes back to sea. Tsunamis can inflict this type of damage because of some unique features. As tsunami waves travel across ocean basins, they may be only a few centimeters high, but they extend down to the ocean floor. This is different than traditional waves, which are only surface features. Tsunamis can also travel hundreds of miles per hour in the open ocean. As these waves approach a coast, the shallowing ocean floor slows the waves down and pushes the water mass upwards. The quicker the ocean floor transitions from deep to shallow, the greater potential for a higher wave height. So tsunamis that experience this sudden shift into shallow water can have the height and momentum to pack a serious punch. Unfortunately, Japan found itself in this scenario. This image shows how abruptly the Japanese islands rise of out of the ocean. Other coastal areas in the region have more gradual slopes. The earthquake on March 11 was the most powerful known to hit Japan, and the tsunami it created had the necessary ingredients to make it such a deadly and destructive force.

(Describer) Fires burn on debris carried by the water. Logos are shown for the Smithsonian and NOAA. Accessibility provided by the US Department of Education.

Accessibility provided by the U.S. Department of Education.