Catastrophes!: Earthquakes, Tsunamis, Tornadoes, and Other Earth-Shattering Disasters

2 Tsunamis: The Sea Rises Up

2 Tsunamis The Sea Rises Up Within minutes, the beach and the area behind it had become an inland sea, rushing over the road and pouring into the flimsy houses on the other side. The speed with which it all happened seemed like a scene from the Bible—a natural phenomenon unlike anything I had experienced before. As the waters rose at an incredible rate, I half expected to catch sight of Noah’s Ark. —Michael Dobbs, Washington Post, December 2004 The Indian Ocean Tsunami: Boxing Day, December 26, 2004 The southern regions of Thailand and the north coast of Sumatra are heavily populated, and during the Christmas holidays, they are crowded with tourists seeking refuge from Northern Hemisphere winters as they enjoy the sun and pristine beaches. The day after Christmas (Boxing Day on the British calendar ) a violent earthquake struck 160 km (100 miles) off the northwest coast of Sumatra. Its moment magnitude was 9.2, the second-largest earthquake ever recorded on a seismograph, and lasted between 8 and 10 minutes, the longest 56 Catastrophes! duration of shaking ever observed. The entire place vibrated by as much as 1 cm (0.5 inches) up and down and triggered sympathetic earthquakes as far away as Alaska. As the Indian plate is pushed under the Burma plate, it produces a huge subduction zone that is responsible for the island nations of Indonesia and Malaysia. The fault line of this plate boundary formed a rupture about 400 km (250 miles) long and 100 km (60 miles) wide, which was located 30 km (19 miles) beneath the seabed—the longest rupture ever caused by an earthquake. The energy released by the quake was about 550 million times more powerful than the atomic bomb that destroyed Hiroshima. Although the earthquake shook Thailand, Indonesia, and Malaysia that morning, many people recovered quickly, or ignored it, and went on with their day. Minutes after the earthquake, however, the effects of the submarine quake showed up on the western shore of Thailand and Indonesia. First, the sea level dropped abnormally low, exposing the coastal reefs and seabed. People ran out for the easy fishing, only to discover to their horror that the unusually low sea level was a trap; suddenly a 30-m-tall (100-foot-tall) seismic sea wave (fig. 2.1), or tsunami, bore down on them. The largest loss of life occurred along the western coast of Indonesia, Malaysia , and Thailand. Waves propagated westward across the Indian Ocean at 500 to 1,000 km/h (310 to 620 mph). Within 90 minutes, waves had reached Sri Lanka and the coast of India. Seven hours later the tsunami reached Africa’s Somalia coast, where the damage and loss of life were worse than in Bangladesh , which was much closer to the source of the waves (but not in the direct path of the main wave propagation). The tsunami was noticed as far as South Africa’s western coast, 8,500 km (5,300 miles) away, and propagated out into the Pacific Ocean, although with less force. The evening of the tsunami Michael Dobbs of the Washington Post (2004) reported this account of the tsunami as it reached Sri Lanka: Disaster struck with no warning out of a faultlessly clear blue sky. I was taking my morning swim around the island . . . when I heard my brother shouting at me, “Come back! Come back! There’s something strange happening with the Tsunamis 57 sea” . . . As I swam to shore, my mind was momentarily befuddled by two conflicting impressions: the idyllic blue sky and the rapidly rising waters. In less than a minute, the water level had risen at least 15 feet—but the sea itself remained calm, barely a wave in sight . . . There are reports of hundreds, perhaps thousands of people missing and drowned in southern Sri Lanka. The coastal road is littered with carcasses of boats and dead dogs. Even a few dead sharks have washed up on the road. We have no water, and no electricity and are practically cut off from the rest of Sri Lanka . . . The holiday that we planned and dreamed about for many months is in ruins. We feel fortunate—fortunate to be alive. News of the tsunami spread around the world. Tourists’ video footage showed horrifying pictures of a wall of water rushing through villages and crushing and sweeping away everything in its path (fig. 2...