What is a tsunami and earthquake?
A tsunami is a huge wave, usually caused by volcanic or earthquake activity under the ocean, in the subduction zone, which can eventually crash onto the shoreline. It is the series of water waves caused by the displacement of a large volume of a body of water like the sea or ocean. The effects on a community can be devastating as it can destroy lives. When the wave enters shallow water, it slows down and its amplitude (height) increases. This causes more destruction than smaller waves because when the wave comes down it has more pressured force than smaller waves. On the other hand an earthquake is a sudden violent shaking of the ground, which creates seismic waves, typically causing great destruction, as a result of movements within the earth's crust or volcanic action on both land and undersea.
What causes an earthquake and tsunami?
The outer crust of the earth is like a jigsaw puzzle. It is broken into huge pieces, all different sizes and shapes called plate tectonics. The plate move around very slowly like air particles. Where the plates meet the grind together, they cause earthquakes and also volcanic eruptions. This is because of convectional currents in the earth’s mantle, which cause the earth’s crust to move in different directions. Magma then rises up towards the crust, when reaching the crust it moves sideways dragging the crust.
When an earthquake, volcano or landslide happens on the ocean floor, water is displaced. This water forms the start of the tsunami. This could also occur if two tectonic plates collide with each other creating an undersea earthquake.
When 1 tectonic plate is dragged beneath another, stress on the boundary causes the edges of the plate to deform and flex. Flexing of the plates displaces huge volumes of water, causing initial tsunami. Within a few minutes a single tsunami splits into two, one travelling out to sea the other to the coast. The tsunami comes ashore and can surge far inland. Often secondary waves are more powerful than initial shocks.
What effects does a tsunami have?
The main impact a tsunami has is flooding. The waters are also able to erode coastal structures. Tsunamis cause damage by two mechanisms: the smashing force of a wall of water travelling at high speed, and the destructive power of a large volume of water draining the land and carrying a large amount of debris with it. A tsunami can also leave devastating long/short term impacts socially, environmentally and economically.
On December 26th 2004 a 15-20 feet tall tsunami with a velocity of 10 knots, struck Indonesia, Thailand, Sri Lanka, Burma, Malaysia, Borneo, India, Madagascar, Kenya, Tanzania, Somalia, South Africa and Bangladesh the worst, all located in the Indian Ocean . This caused many deaths, injuries, missing and displaced, leaving people devastated and depressed. The killer wave killed over 230,000 people in fourteen countries. The tsunami struck the northern part of Sumatra, Indonesia approximately 15 minutes after the earthquake occurred. Thailand was hit 2 hours even though it was closer to the epicentre, but the tsunami started to slow down in the Andaman Sea. It took 90 minutes-2 hours to reach the coast of India and Sri Lanka Island. Somalia was struck 7 hours later. Then it reached the southern tip of Africa, 19 hours after the earthquake.
The tsunami was caused by an undersea mega thrust earthquake that occurred at 07:58:53 local time, on Sunday 26th of December 2004, with an epicenter off the west coast of Sumatra, Indonesia. A mega thrust earthquake is an earthquake that occurs in the subduction zone of a destructive plate boundary. The earthquake had a magnitude of 9.5, and was the third largest earthquake ever recorded on a seismograph. A seismograph is an instrument that is used to accurately record the earth’s movement and to detect earthquakes. The giant wave is known as ‘The Great Sumatra-Andaman Earthquake’ that