1. TSUNAMI

2. We now know that, directly or indirectly, plate tectonics influences nearly all geologic processes, past and present.

3. With little or no warning, an earthquake or volcanic eruption can unleash bursts of energy far more powerful than anything we can generate. Tsunamis can be one such effect.

4. While we have no control over plate-tectonic processes, we now have the knowledge to learn from them.

5. In geologic terms, a plate is a large, rigid slab of solid rock. The word tectonics comes from the Greek word "to build." Plate tectonics refers to how the Earth's surface is built of plates.

6. The theory of plate tectonics states that the Earth's outermost layer is fragmented into a dozen or more large and small plates that are moving against one another as they ride atop hotter, more mobile material.

9. About two thirds of the Earth's surface lies beneath the oceans. Data gathered by oceanographic surveys led to the discovery that a great mountain range, called the global mid-ocean ridge, virtually encircles the Earth.

10. Rising an average of about 4,500 meters above the sea floor, the mid-ocean ridge overshadows all the mountains in the United States except for Mount McKinley in Alaska.

11. Computer generated topographic map of a segment of the Mid- Oceanic Ridge…

12. During the 20th century, greater use of earthquake- recording instruments (seismographs) enabled scientists to learn that earthquakes tend to be concentrated in certain areas, most notably along the oceanic trenches and spreading ridges.

16. Tsunamis are usually caused by underwater earthquakes. These often occur offshore at subduction zones (places where a tectonic plate is gradually slipping under a continental plate).

18. Part of the sea floor can snap upward abruptly, while other areas sink downward, when sections of the plates that have been locked together for a while move suddenly under the strain.

20. In the instant after such an underwater earthquake, the shape of the sea surface mirrors the new contours of the sea floor-- some areas of water are pushed upwards, and others sink.

22. This starts a series of waves that rush outwards-- the beginning of a tsunami. These waves travel very far and very fast (more than 500 miles/hour, or the speed of a jet airplane).

23. At first, out at sea in deep water, the waves are very far apart-- sometimes hundreds of miles— and their crests are not very high, perhaps only a few feet above the rest of the surface …

25. Seen from a passing ship or low-flying plane, they would probably not even be noticeable…

26. But, when a tsunami leaves deep water and approaches the shore, it slows down and its height grows. The wave crests also squeeze closer together.

28. Depending on the shapes of the sea floor off the coast, a tsunami hitting the coast may appear as a series of towering walls of water that can level buildings.

30. Contrary to many beliefs, most tsunamis do not result in giant breaking waves (like normal surf waves that curl over as they approach shore). Rather, they come in much like very strong tides.

31. The force of an oceanic earthquake also sends out tsunami waves in all directions away from the epicenter.

32. Epicenter of earthquake Tsunami Waves

33. Tsunamis can spread across an ocean, as seen in the next diagrams- a tsunami from its origin off the coast of South America reached Hawaii in about ten hours.

36. The most powerful earthquake in 40 years erupted under the Indian Ocean near Sumatra on Dec. 26, 2004.

38. It caused giant, deadly waves to crash ashore in nearly a dozen countries, killing over 150,000 people.

42. Measured at 8.9, it was the strongest earthquake worldwide since a 9.2 quake hit Alaska in 1964.

44. Billions of dollars of damage was caused by the Asian tsunamis caused by the earthquake. It will be the costliest disaster in world history.

48. Up on the northern tip of the island of Sumatra, Indonesia, close to the epicenter of the quake, the regional capital Banda Aceh was devastated.

51. The first tsunamis hit early in the morning… Locals described a wall of water, slamming into the coastline.

54. Some felt the quake first, others saw the sea sucked away from beaches only to return minutes later as a wall of water up to 30 feet high.

55. Tsunami moves toward land Kalutara, Sri Lanka…

56. Tsunami receding, Kalutara, Sri Lanka.

57. A surge of water swept through beachfront hotels. There were loud crashes as buildings collapsed.

60. Eyewitnesses say two tidal waves struck early in the morning. The force of the second wave was so strong it threw people and vehicles in its path.

62. Among the dead were tourists from many nations. It was a record year for the tourist industry and hotels along the coasts were fully booked, filled with foreign vacationers.

64. Banda Aceh, Indonesia prior to the tsunami…

65. Satellite image after the tsunami…

66. Banda Aceh harbor before…

67. …after

68. Sickness and infection remain a major concern. The countries are ravaged- not just homes but crops and means of earning a livelihood, such as fishing boats, have been destroyed.

73. Nations around the world responded in sending aid, manpower, food and water. The United States government donated $350 million and independent charity organizations have sent additional aid, totaling over $1 billion.

75. But recovery will be slow…

76. TSUNAMI Created for Edmond Public Schools