tsunamis tidal waves, but scientist think the term is misleading because the waves are not cause by the tide. Tsunamis may build to heights of more than 100 feet (30 m) when they reach shallow water near shore. In the open ocean, tsunamis typically move at speeds of 500 to 600 miles (800 to 970 km) per hour. They can travel great distance while diminishing little in size and can flood coastal areas thousands of miles from their source. Another form of tsunamis is called a storm surge, in which giant waves are whipped up by a storm. In 1970 a storm surge and cyclone hit Bangladesh, killing 266,000 people. It returned again in 1985, killing another 10,000 people...