NATURAL HAZARDS & DISASTERS

1. NATURAL HAZARDS & DISASTERS • WHAT ARE HAZARDS? • A hazard is any event that could threaten or pose injury to people and their environment • WHAT ARE DISASTERS? • Disasters are sudden , extremely unfortunate events that affect many people negatively. They are caused by natural occurrences such as earthquakes and floods. They can also be caused by accidents brought about improper handling of faulty maintenance of man made items such as airplanes , ships and buildings.

2. TYPES OF NATURAL HAZARDS IN THE CARIBBEAN • EARTHQUAKES • DROUGHTS • FLOODS • HURRICANES • LANDSLIDES • VOLCANIC ERUPTIONS

3. A Landslide is the downward movement of a large mass of loose soil and rocks by the force of gravity . Its velocity or speed can range from moderate to very rapid, depending on the steepness of slope, the weight of material being moved or the consistency or water content of the material. LANDSLIDES

4. CAUSES OF LANDSLIDES • Landslides are caused in several ways. The commonest occur on slopes where there are two rock types . These are a layer of permeable rock or soil , resting on top of a layer of impermeable rock. When the rains falls, the top layer may become saturated . This loosens the contact between layers. This loose heavy mass of material may then slide down the lubricated plane, thus forming a landslide.

5. EFFECTS OF LANDSLIDES • Burial of homes , livestock and crops by debris. • Blockage or breakage of communication lines. • Displacement of water from rivers, lakes ponds and drains that can lead to flooding. • The landscape can become scarred and unsightly. • Loss of valuable top soil. • Removal of vegetation / forest cover.

6. EARTHQUAKES • An earthquakes is any sudden large scale tremor or movement of the earth’s crust. It effects can be felt over long distances and large areas such as across a continent.

7. CAUSES OF EARTHQUAKES • Rubbing together of crustal plates that can lead to friction. • The displacement of land during faulting. • Movement of magma below and within the earth’s crust. • Man activities such as drilling for oil and using explosives in quarrying,

8. EFFECTS OF EARTHQUAKES • Tremors or shaking of the round . This can lead directly to the collapse of buildings and infrastructure such as roads and bridges. • Landslides , rockfalls and mudflows. • Tsunamis or large ocean waves • Broken gas pipelines and fallen electricity poles can lead to fires.

9. EFFECTS OF EARTHQUAKES

10. TSUNAMIS • A tsunami is a long high sea wave. It is caused by an earthquake in the ocean’s floor which results in a shift of the sea bed. • This shift triggers giant waves travel at speeds of up to 500km/hr and above. • These waves are circular in motion and travel outwards , similar to ripples. • On reaching shore the tsunamis recedes more than normal at low tide. On reaching shallow waters near coastlines, a tsunami rears to gigantic heights.

13. FLOODS • A flood is a body of water that temporarily covers land that is usually dry. A flood is also defined as a mass of unwanted water in places that are considered useful to man when dry.

14. CAUSES OF FLOODS • The overflowing of the river channel onto the flood plain and nearby land s\after a period of heavy or prolonged rainfall. • The displacement of water in a river , lake , pond or drain . This can occur when a landslide , mudflow or debris empties into these structures. • Movement of waves beyond the high tide level . This is often the cause with a tsunamis or hurricane that can large waves to be brought far inshore. This is sometimes referred to as coastal flooding.

15. EFFECTS OF FLOODS • Drowning of people and livestock. • Crops become water logged. • Damage or destruction of buildings and infrastructure. • Pollution of fresh water sources. • Spread of diseases such as cholera and leptospirosis. • Removal of topsoil. Leaving the land barren.

17. DROUGHTS • Droughts occurs when a geographical area experiences an unusual shortage of water. It is associated with hot and dry conditions with little or no rainfall.

18. CAUSES OF DROUGHTS • Climatic cycle change that can bring about dry , hot conditions to an area which was once wet. • Unusual climatic phenomena that can temporarily affect a place such as El Nino. • Global warming due to pollutants in the atmosphere.

19. EFFECTS OF DROUGHTS • Decreasing local water supply for drinking , cooking etc. • Negative effects on agriculture such as reduced crop yields and milk production. • Famine and hunger. • Increased soil erosion by wind • Widespread bush fires. • Endangered animal life.

20. HURRICANES • A hurricane is an intense tropical storm with a central low pressure area which carries high gusty winds exceeding 117km/hr. . Thunder , lightning , dark clouds and heavy rainfall are common features of a hurricane.

21. CAUSES OF HURRICANES A hurricane in the Caribbean usually starts as a tropical wave off the west coast of Africa. There , the warm seawater evaporates and is absorbed by the surrounding air. The warm moist air rises , lowering the atmospheric pressure of the air beneath. Air tend to move from areas of high pressure to areas of low pressure , creating winds and downdraughts. As evaporation increases the central pressure become s lower and the wind speed higher. The system then grows into a depression , then a tropical storm and finally a hurricane.

22. Eye Wall Eye

23. FORMATION OF A HURRICANE

24. SOME EFFECTS OF HURRICANES • Heavy or prolonged rainfall that can lead to flooding. • High gusty winds that can destroy buildings , pull down power lines and destroy crops. • Destruction of beaches and coral reefs. • Economic setbacks e.g. tourist industry • Rainfall that can lead to landslides and mudflows.

26. VOLCANOES • A volcanic eruption is the expulsion of magma from below the earth’s crust onto its surface . Most eruptions are violent or explosive since the magma is usually compressed with a mixture of gases below the earth’s surface.

28. CAUSES OF VOLCANIC ERUPTIONS • Where crustal plates move towards each other over the earth’s mantle. When the plates meet , the heavier oceanic crust is forced into the mantle , where it melts and creates a large amount of magma. The magma being volatile moves up and through the continental crust until it reaches the surface with an explosive force.

29. EFFECTS OF VOLCANIC ERUPTIONS • Lava flows can bury and burn whole cities and towns. • Toxic gases released during eruptions can lead to respiratory problems. • Rocks and debris from the blast can destroy anything in their paths. • As the magma moves below the earth’s surface . It can lead to earthquakes.

30. VOLCANIC ERUPTIONS

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