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Droughts are prolonged periods of lack of rain.

It may last for a week or even several years

E.g.: Sahel region, south of Sahara Desert - experience excessive evaporation, great heat and little rain.


 Causes  Of Drought
(i) unusual warm ocean currents - which cause heatwaves.

(ii) man through activities such as deforestation and overgrazing.


 Consequences Of Drought
1. Desertification.

Desertification is the degradation of land in arid, semi-arid and dry sub-humid areas due to the influences of human activities and climatic variations on dryland ecosystems.


2. Famine


3. Food shortage & crop failure


 Photo Gallery




 FLOODS           [Back to top]


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 Types Of Floods
(i) River floods

- Occur when swollen rivers overflow the banks.

- Often caused by heavy rain or melting snow.

- E.g. Hwang He River, China


(ii) Coastal floods

- Occur when storms, high tides, tsunamis or sea surge flood coastal areas.

- E.g. Bangladesh and the Philippines


(iii) Seasonal floods

-Occur when streams overflow the banks during the wet season.

- E.g. Nile floods in Egypt


(iv) Flash floods

- Floods that occur suddenly, due to heavy downpour for several hours, or poor drainage system.

- E.g.: Brisbane, Kuala Lumpur.


 Photo Gallery - Flooding





 TROPICAL STORMS           [Back to top]


Hurricanes, Typhoon, Tropical Cyclones & Willy Wilies


 A. Formation of Tropical Storms


  1. Hurricanes form over warm tropical seas.

  2. Wind from opposite directions meet and begin to spiral upwards over an area of low pressure.

  3. Water vapour, carried from sea below, rises, becomes warm and forms cumulonimbus clouds.

  4. As air becomes warmer, it rises more quickly.

  5. This movement of rising air sucks in more air at the bottom and begins to spiral faster and faster.

  6. Wind speeds can reach up to 320km/hr.

  7. But the centre of the storm (the'eye') is a quiet, still area, with only light winds.

  8. Hurricanes only die out over land (when there is no water to supply to the storm).


 B. Hurricane Areas




 C. Effects Of Tropical Storms On Coastal Areas

  • Storm surge

Fast blowing winds can raise the sea level by about 1m beneath the 'eye', and creates a huge mound of water.

As a hurricane moves to the coast, the mound of water piles up against the land.

Destructive surge of water can rip boats and batter buildings.


Pic source:

Storm surge



 D. Result



  • Introduction on Hurricanes

  • Parts of a hurricane

  • Effect - Video: virtually fly through a hurricane
    (Real Media Player/Windows Media Player) 

  • Phenomena- Video: watch the formation of Hurricane Andrew
    (Real Media Player/Windows Media Player) 

  • Science - video: a Florida homeowner talks about Hurricane Andrew's ordeal, satellite data animations of Hurricane Luis in progress
    (Real Media Player/Windows Media Player) 


 E. Difference Between A Hurricane And A Tornado





 Photo Gallery