OBJECTIVES To define natural disaster To list down the four different types of natural disaster To explain the causes of an earthquake and tropical cyclone To list down the effects/problems causes by an earthquakes and tropical cyclone To describe measures to minimize the damages caused by an earthquake and tropical cyclone
Prior Knowledge The three layers of the Earth’s structure : core, mantle, and crust. The plates movements and its boundaries, and the distribution of the world's volcanic and earthquake areas. The students must have some background knowledge of the followings:
NATURAL DISASTER DIFFERENT TYPES OF NATURAL DISASTER DEFINITION OF NATURAL DISASTER
WHAT IS A DISASTER? A DISASTER IS AN EVENT WHICH BRINGS GREAT TROUBLE AND HARDSHIP NATURAL DISASTER OCCURS BECAUSE OF UNUSUAL MOVEMENTS OF THE EARTH, WIND, OR WATER
Tsumani Wave A tsunami wave flows toward the shore after a small earthquake in the Sunda Strait of Indonesia. Tsunamis are often mistakenly called tidal waves, but they are not caused by the gravitational forces involved in tides. Instead, tsunamis are believed to be caused by a tilting of the ocean floor, undersea landslides, or undersea volcanic eruptions
Effects and problems caused by an earthquake Each year about 500,00 earthquakes are recorded and of these about 1000 are strong enough to cause damage. As a result of these, roads and railways twist and buckle. Sewers, gas and water pipes and electricity cables break. Buildings crack and fall down. In the worst earthquakes, whole towns have been destroyed, and many people killed or injured.
The streets are made wide so that building will not block them if they fall.
Open spaces are left in towns, so that people can go to them out of reach of falling buildings.
People can be trained to know what to do should an earthquake occur and towns should have trained people, equipment, medical and food supplies, to organize the evacuation of the people.
Scientists, with their seismometers and many other delicate instruments, monitor the situation day and night.
TROPICAL CYCLONES What are tropical cyclones? Names given to tropical storms Where do tropical cyclone born? Case Study: Tropical cyclones in Bangladesh Tropical cyclone around the world How tropical cyclone is formed? How do tropical cyclone gains its energy?
Meteorologists use satellite images taken in infrared light to determine the heat of areas of the atmosphere. The data is translated into a visible image, which is often enhanced, or colored with shades representing temperatures. In enhanced images, red usually represents the hottest temperatures and violet usually represents the coolest temperatures.
It is formed when air becomes warm and begin to rise. Minute water droplets form on the rising air. They make huge cumulo-nimbus clouds which hold thousands of tones of water. They can reach 15km high.
Tropical cyclones form over water when a mass of thunderstorms becomes organized and spirals in toward the storm’s center, or eye. The storm’s highest winds, strongest thunderstorms, and heaviest rain, occur just outside the eye in the region called the eye wall. In the eye itself, winds are usually light and skies are partly cloudy.
Tropical cyclones derive their energy from the transfer of heat from the warm water and from the latent heat given up to the system during condensation. Tropical cyclones dissipate when they are cut off from their energy sources either by moving over cold water or a large land mass. Although tropical cyclones often take erratic paths, the prevailing easterly winds in the tropics tend to steer tropical cyclones westward or northwestward until they leave the tropics, then the prevailing westerlies tend to sweep them northeastward.
Case Study: TROPICAL CYCLONES IN BANGLADESH How do tropical cyclone bring disaster to Bangladesh? 1991 Cyclone In Bangladesh How did the cyclone been spotted? The worst affected areas hits by the cyclone in Bangladesh Problems caused by tropical cyclone
The worst affected areas hits by the cyclone in Bangladesh
Most weather services use satellite information in their forecasts. Pictures such as this one of Hurricane Gloria reveal patterns and movement that provide clues about what the storm might do next. The weather is continuously monitored and photographed by satellites worldwide, but it is still difficult to predict weather because of the many variables involved. Infrared sensors help meteorologists to interpret the pictures by determining the height and temperature of the clouds.
The worst affected area was between Chittagong and Cox’s Bazaar along the coast, and the off-shore islands of Sandwip, Kutubdia and Maheshkali.
The whole densely populated area was covered by tidal wave.
The worst affected areas hits by the cyclone in Bangladesh
PROBLEMS CAUSED BY TROPICAL CYCLONES -WITH REFERENCE TO THE BANGLADESH GOVERNMENT
The winds and waves battered the coastal areas for about four hours.
The cyclone destroyed crops, huts, roads, bridges and electricity pylons.
The salt water destroyed rice harvests and contaminated drinking water.
Life after the cyclone was more difficult without food, drinking water and shelter.
PROBLEMS CAUSED BY TROPICAL CYCLONES PROBLEMS CAUSED BY TROPICAL CYCLONES -WITH REFERENCE TO THE BANGLADESH Measures to minimize the problems of tropical cyclone in Bangladesh
Measures to minimize the problems of tropical cyclone in Bangladesh
More than 120,000 were killed and millions left homeless in April 1991 when a powerful cyclone struck the coastal areas in the Ganges delta.
Little could be done to solve problem of tropical cyclone in Bangladesh, nevertheless, aids, in the form of money, medicines, food, clothing, shelters, doctors, nurses and other voluntary workers came to Bangladesh through the United Nation and from individual countries and organization.
Countries are learning to co-operate speedily in times of disaster and to share their wealth and expertise however, more must be done to help to protect the people from natural disasters.