|Tsunami are waves that can and do cause great damage and considerable loss of life. For example, the estimated 35 foot high tsunami generated by the 1883 eruption of Krakatoa volcano in Indonesia killed more than 35,000 people. A tsunami that hit Japan in 1703 killed more than 100,000 people. In 1755, a tsunami generated by an earthquake caused 50,000 people to lose their lives. More recently, in 1998 a magnitude 7.1 earthquake produced a tsunami that killed 2,200 people in Papua New Guinea. More recently, Since 1990, 82 tsunami have been documented.|
|Foundation of school building remaining after tsunami hit village in New Gunea|
|What is a tsunami?|
|Tsunamis are shallow water waves. That is they are waves that occur in water shallower than 1/20th of their wavelength. Wavelengths of tsunamis reach up to 125 miles. Consequently, these waves may drag on the bottoms of the deepest oceans. Periods of tsunamis range from 10 to 20 minutes, that is, it may take 10 to 20 minutes for waves to hit the shoreline following the first wave . Heights of tsunami in the open ocean average average between one to two feet. Tsunami may reach speeds of over 400 miles/hour.|
|How are tsunamis generated?|
|Tsunamis, unlike typical waves in the ocean that are generated by wind, are produced by some disturbance of the seafloor. Earthquakes commonly generate tsunami. Volcanoes erupting, submarine landslides, and meteorite impacts also produce tsunamis. Tsunamis are not generated by tides. Therefore, it is incorrect to refer to these powerful waves as "tidal waves". Tides are generated by the gravitational attraction between the earth, the moon, and the sun.|
|Where are tsunamis likely to occur?|
Study the map above showing the locations of some recent tsunami in the Pacific Rim. Tsunami are not common in the Atlantic Ocean.
Answer the following question:
1. Why are tsunamis more likely to be generated in the Pacific Ocean than in other oceans?
A. Stronger wind in the Pacific
|The map of the Pacific Rim shows the locations of relatively recent earthquakes. The colors of the dots indicate the depths of occurrence of the earthquakes. Deep earthquakes are indicated by red dots; intermediate earthquakes are shown by purple and blue dots; and shallow earthquakes are green, yellow, and orange. The Pacific Rim is the most seismically active area in the world. Most tsunamis are generated by earthquakes. Consequently, tsunamis are more likely to occur in the Pacific Rim.|
|How fast do tsunami move?|
|Examine the map showing the location
of the 1960 Chilean earthquake and the time ( in hours) that it took the
tsunami generated by the earthquake to reach different coastal areas of
the Pacific. Each white line with a number shown on the map represents the
time required for the tsunami to reach that area of the Pacific.
2. If the distance from the location of the earthquake to the Los Angeles coastal area is approximately 5000 miles, what was the speed of the tsunami generated by the 1960 Chilean earthquake?
|3. What is the name of the island
chain along which the earthquake and subsequent tsunami were generated?
5. What happens to the wave when it hits the coastline?
A. Dissipation (weakening) completely along
6. In which area would the wave move the fastest?
|7. Starting from the southwestern tip of the
island, measure northeast to the inundation line and determine approximately
how many meters of island was inundated (covered) with water as the tsunami
hit the island? (Scale bar shows distances from 0-1km).
8. What impact did the tsunami have on the beaches of Okusiro Island?
9. If the tsunami approached the island from the west, how did the eastern side of the island become inundated?
A. A second tsunami approached from the east
2004 Indonesia/SummatraTsunami Simulations, Videos, and Photos (under construction) THE SOURCES FOR ALL OF THE INFORMATION PRESENTED BELOW STILL NEED TO BE CREDITED
Below are images from the 2004 Indonesia Tsunami. The images and captions are taken from the following website.
December 26, 2004 tsunami disaster
Causes and Effects:
On December 26, 2004, a large (magnitude 9.0) earthquake occurred off the western coast of Sumatra in the Indian Ocean. The earthquake was caused by the release of stresses accumulated as the Burma tectonic plate overrides the India tectonic plate. Movement of the seafloor due to the earthquake generated a tsunami, or seismic sea wave, that affected coastal regions around the Indian Ocean. The northwestern Sumatra coastline in particular suffered extensive damage and loss of life.
Banda Aceh is at ground zero of thetsunami disaster. On December 26, 2004, the city was only 155 miles (250 kilometers) from the magnitude 9.0 earthquake epicenter. The magnitude of this tsunami is that it goes on for hundreds of miles in both directions. The tsunami came in as a huge wall of water that didn't break as a wave for something like three-quarters of a mile [1.2 kilometers]. Within minutes of the quake, millions of unsuspecting people were engulfed by a wall of seawater reported to have been as high as 60 feet (18 meters). The tsunami swept everything before it for up to five miles (eight kilometers) inland. When the ocean receded entire communities had disappeared and tens of thousand people were dead.
These maps show modeled maximum wave height (top) and travel time (lower) for the Indian Ocean Tsunami of December 26, 2004. Although the epicenter of the earthquake that triggered the tsunami was near the northern tip of Sumatra, the sea floor shifted along an arc stretching about 1200 km to the north. This shifting pushes a mass of water across the Indian Ocean.
The top map shows the maximum wave height that likely occured when the wave came ashore. The coastline of Sumatra, near the fault boundary, received waves over 10 meters tall, while those farther away (Sri Lanka and Thailand) were caught by waves over 4 meters. On the other side of the Indian Ocean, Somalia and the Seychelles were struck by waves approaching 4 meters in height. Travel times (lower) ranged from minutes (Sumatra) to 8 hours (Somalia) or more.
This is the fourth largest earthquake in the world since 1900 and is the largest since the 1964 Prince William Sound, Alaska earthquake. In total, more than 283,100 people were killed, 14,100 are still listed as missing, and 1,126,900 were displaced by the earthquake and subsequent tsunami in 10 countries in South Asia and East Africa. The many aftershocks were as high as magnitude 6
The plate shift actually moved the island of Sumatra 100 feet to the southwest. Entire islands were permanently lifted several feet up. The earthquake created a measurable shift in the earth's rotation.
DigitalGlobe’s Quickbird satellite captured an image of the devestation around Kalutara, Sri Lanka (top), on December 26, 2004, at 10:20 a.m. local time—about an hour after the first in the series of waves hit. [A Quickbird image taken on January 1, 2004 (lower), shows the normal ocean conditions.] Water is flowing out of the inundated area and back into the sea, creating turbulence offshore. Some near-shore streets and yards are covered with muddy water. It is possible that the image was acquired in a "trough" between wave crests. Imagery of nearby beaches shows that the edge of the ocean had receded about 150 meters from the shoreline.
Nearly three weeks after an earthquake triggered the deadly Indian Ocean tsunami on December 26, 2004, satellite analysis continues to illustrate the magnitude of the disaster. This pair of ASTER images contrasts before and after views of a portion of the western coastline of Thailand in the Phang-Nga province, about 50 kilometers north of the island of Phuket. In these images, vegetation is dark red, while bare earth is grey. On December 31, five days after the waves swept ashore, large sections of the shoreline are grey, stripped of vegetation or covered in mud and sand. Water has broken through several places along the northern beach. Tiny fingers of blue water slice into the land where no inlet existed in the image on the right.
Satellites continue to acquire imagery of areas severely damaged by the tsunami of December 26, 2004. This image of Meulaboh, Indonesia, was collected on January 7, 2005, by DigitalGlobe’s QuickBird satellite. Meulaboh is located on the coast of Sumatra, roughly 150 kilometers (93 miles) from the epicenter of the magnitude 9.0 earthqukae that generated the tsunami. The image shows where the tsunami washed over a narrow peninsula, eroding the beach and destroying many of the town’s buildings.
The December 2004 tsunami destroyed an estimated one-third of the buildings in Banda Aceh.
Many eyewitnesses have compared the post-tsunami scene in Banda Aceh to that of Hiroshima, Japan, after it was hit by an atomic bomb during World War II.
A soldier wears a mask to protect himself from disease and the stench of decaying bodies.
This fishing boat landed on the main street of Banda Aceh several miles from the sea.
A survivor searches the rubble of Banda Aceh, where about half of the population was killed by the December 26 tsunami.
The brown, barren area at the foot of this inland hill marks where the tsunami slammed into it.
More than two weeks after the tsunami, thousands of corpses remain, wrapped but in the open. It will take months to dispose of them all.
About 50,000 bodies have been found in Banda Aceh. Thousands more are being reported each day.
Visit the websites listed below for simulations, videos, and photos of the recent devastating Indonesia/Summatra tsunami.