quent seismic and volcanic activity, this zone that circles the Pacific is known as the “Ring of Fire.” On the east, the Pacific Plate encounters the Nazca Plate in the south and the North American Plate in the north. On the west coast of South America, the Nazca and South American plates come together and are the source of considerable seismic activity there. In the southwestern Pacific, it is the intersection between the Pacific and Australian plates that gives rise to seismic activity. The strong earthquake belt that runs roughly east-west through the Mediterranean and Central Asia occurs along the intersection of the African and Eurasian plates.
In addition to shaking the land, earthquakes in or near the sea can create extreme waves. Scientists believe that some of the largest waves ever experienced on earth were generated by earthquakes in prehistoric times. In the decade from 1990 to 2000, 14 seismic sea waves hit somewhere in the world, resulting in extensive damage and considerable loss of life. In the Pacific region over the last 2,000 years, nearly 500,000 people have died from tsunami; in contrast, the 2004 Sumatra tsunami in the Indian Ocean alone exerted a death toll now estimated at more than 280,000 persons.1
Ironically, the Indian Ocean has had little tsunami activity in recent history, although the circular area south from Myanmar to Indonesia and east and north along the Philippines bounds the Eurasian Plate—a hotbed of seismicity over the last 100 years. There have been nine magnitude 8 earthquakes since 1900. The magnitude 9 Sumatra-Andaman Island earthquake of December 26, 2004, occurred along this fault zone. The lack of tsunami associated with these numerous earthquakes created a false sense of security in the region.
Seismic sea waves—often referred to incorrectly as “tidal waves”—are called tsunami, which is Japanese for “large wave in harbor,” to distinguish them from tide waves. The same spelling is used for the singular or plural form. Tsunami are quite different from storm-generated waves in that they have long wavelengths between 6 and 300 miles. Recalling from Chapter 1 that “deep” water for a wave is defined as a