Tsunamis • Giant waves generated by an underwater disturbance that cause destruction to coastal areas • Japanese for“harbour wave” • Often incorrectlycalled “Tidalwave”
Tsunamis • Waves will travel outward in all directions • Time between wave crests may be from 5 to 90 minutes • Wave speed in the open ocean will average 450 miles per hour. • Heights of over 100 feet recorded
Tsunamis • When created, it has a very long wave length and short wave height. • As it approaches shallow coastal waters, length is compressed and heights are increased • Wave becomes unbalanced and topples
Tsunamis • Rapid changes in the water level are an indication of an approaching tsunami. • Arrive as a series of successive crests (high water) and troughs (low water) • After a severe earthquake on November 18, 1929, in the Grand Banks of Newfoundland • generated a tsunami that caused considerable damage and loss of life at Placentia Bay, Newfoundland.
Boxing Day Tsunami • Triggered by a 9.3 underwater earthquake off the coast of Indonesia • Killed over 230 000 people • A series of deadly waves up to 30 m high • One of the deadliest natural disasters in human history
Predicting Tsunamis • It can be difficult to predict a tsunami • A sharp swell is the first sign, followed by a receding shoreline • Then the first massive wave hits. The third to eighth waves are usually the largest • One of the best ways to predict a tsunami is to monitor earthquakes
Survive it! • In groups, brainstorm and research ways to survive either an earthquake OR a tsunami. • Could include structural changes to buildings, or survival kits