THE TSUNAMI-{ASWIN SAMBHU.P.R}

THE TSUNAMI : 

THE TSUNAMI DONE BY : ASWIN SAMBHU.P.R

Slide 2: 

A tsunami is a series of waves that is created when a large volume of a body of water, such as an ocean, is rapidly displaced. The Japanese term is literally translated into "(great) harbor wave."

Slide 3: 

A tsunami can be generated when converging or destructive plate boundaries abruptly move and vertically displace the overlying water. It is very unlikely that they can form at divergent (constructive) or conservative plate boundaries. This is because constructive or conservative boundaries do not generally disturb the vertical displacement of the water column. Subduction zone related earthquakes generate the majority of all tsunamis. CAUSES OF TSUNAMI’S

Slide 4: 

Tsunamis have a small amplitude (wave height) offshore, and a very long wavelength (often hundreds of kilometers long), which is why they generally pass unnoticed at sea, forming only a slight swell usually about 300 mm above the normal sea surface. They grow in height when they reach shallower water, in a "shoaling" process described below. A tsunami can occur at any state of the tide and even at low tide will still inundate coastal areas if the incoming waves surge high enough. CHARACTERISTICS OF TSUNAMI

Slide 5: 

While everyday wind waves have a wavelength (from crest to crest) of about 100 metres (330 ft) and a height of roughly 2 metres (6.6 ft), a tsunami in the deep ocean has a wavelength of about 200 kilometres (120 mi). This wave travels at well over 800 kilometres per hour (500 mph), but due to the enormous wavelength the wave oscillation at any given point takes 20 or 30 minutes to complete a cycle and has an amplitude of only about 1 metre (3.3 ft). This makes tsunamis difficult to detect over deep water. Their passage usually goes unnoticed by ships.

Slide 6: 

As the tsunami approaches the coast and the waters become shallow, the wave is compressed due to wave shoaling and its forward travel slows below 80 kilometres per hour (50 mph). Its wavelength diminishes to less than 20 kilometres (12 mi) and its amplitude grows enormously, producing a distinctly visible wave. TSUNAMI’S APPROACHING THE COST

Slide 7: 

Since the wave still has a wavelength on the order of several km (a few miles), the tsunami may take minutes to ramp up to full height, with victims seeing a massive deluge of rising ocean rather than a cataclysmic wall of water. Open bays and coastlines adjacent to very deep water may shape the tsunami further into a step-like wave with a steep breaking front.

Slide 8: 

SIGNS OF APPROACHING TSUNAMI There is often no advance warning of an approaching tsunami. However, since earthquakes are often a cause of tsunami, any earthquake occurring near a body of water may generate a tsunami if it occurs at shallow depth, is of moderate or high magnitude, and the water volume and depth is sufficient.

Slide 9: 

A tsunami cannot be prevented or precisely predicted—even if the right magnitude of an earthquake occurs in the right location. Geologists, oceanographers, and seismologists analyse each earthquake and based upon many factors may or may not issue a tsunami warning. However, there are some warning signs of an impending tsunami, and there are many systems being developed and in use to reduce the damage from tsunami. One of the most important systems that is used and constantly monitored are bottom pressure sensors. These are anchored and attached to buoys. Sensors on the equipment constantly monitor the pressure of the overlying water column. This is deduced through the calculation: Warnings and prevention

Slide 10: 

On 26 Dec 2004, 00:58:53 UTC (7:58:53 am local time), a magnitude 9.0 earthquake occurred off the west coast of northern Sumatra, Indonesia. The epi-centre was located under sea water at 3.32 N 95.85 E. This is the fourth largest earthquake in the world since 1900. The earthquake generated tsunamis which swept across the Indian Ocean within hours. 26 DECEMBER 2004

Slide 11: 

Over 120,000 people lost their lives in this disaster. Areas near to the epicentre in Indonesia, especially Aceh, were devastated by the earthquake and tsunamis. The tsunamis also affected Phuket and surrounding areas in Thailand, Penang in Malaysia, Sri Lanka, India, and places as far as Somalia in Africa.

Slide 12: 

Tsunami or the harbour wave struck havoc in the Indian Ocean on the 26 December 2004. The wave was the result of the earthquake that had its epicenter close to the western boundary of Sumatra. The magnitude of the earthquake was 9.0 on the Richter scale. As the Indian plate went under the Burma plate, there was a sudden movement of the sea floor, causing the earthquake.

Slide 13: 

The ocean floor was displaced by 10-20m and tilted in a downwardly direction. A huge mass of ocean water flowed to in fill the gap that was being created by the displacement. This marked the withdrawal of the water mass from the coastlines of the landmasses in the south and southeast Asia. After thrusting of the Indian plate below the Burma plate, the water mass rushed back towards the coastline. Tsunami traveled at a speed of about 800km. per hour, comparable to speed of a commercial aircraft and completely washed away some of the islands of the Indian ocean.

THANK YOU : 

THANK YOU