The Ever-Present Threat of Tsunamis
06 June 2011
A tsunami wave washes away houses in Kesennuma, Miyagi prefecture, on March 11
BOB DOUGHTY: This is SCIENCE IN THE NEWS in VOA Special English. I’m Bob Doughty.
FAITH LAPIDUS: And I’m Faith Lapidus. This week, we tell about tsunamis -- the deadly sea waves often caused by earthquakes.
BOB DOUGHTY: People in Japan call them “harbor waves.” Tsunami is a two-character Japanese word. Tsu means harbor and nami means wave. Tsunamis happen after an earthquake strikes, either near or under the ocean. The earthquake displaces a large amount of water in the ocean. Waves then rush inland quickly and powerfully, causing death and destruction.
Scientists say that strong earthquakes under the sea are responsible for eighty to ninety percent of all tsunamis. Volcanic explosions can also cause a tsunami. So could a large piece of land sliding into the water or when a rock from space strikes the ocean. There have been three major tsunamis worldwide in the past seven years. Generally, a major tsunami happens only once every ten years.
FAITH LAPIDUS: In the deep ocean, a tsunami wave may rise up only about three hundred millimeters. In fact, people on a boat at sea may not even know that a tsunami wave has just moved past them. Tsunamis are long waves that can travel great distances very quickly - some move at over eight hundred kilometers an hour. They can cross an ocean in less than a day.
最新
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25