Geography Revision


Natural Hazards- a natural event that threatens people or has potential to cause damge or harm.

Tropical storms- Hurricanes,typhoons,cyclones are particular tropical revolving storms. They're intense, destructive, low pressure weather systems. they have very strong winds over 120km/h and torrential rain. They bring chaos and misery.

Rules for studying weather

1. Hot air rises. as it does so it cools.

2. Cold air sinks. As it does so it heats up.

3.Air pressure is a measure of the air pressing down on us.

4. If air is rising, it creates low pressure at the ground surface.

5. If air is sinking, it creates high pressure at ground suface.

6. Air moves from high pressure to low pressure. Air moving at ground surface is called wind.

7. Warm air can hold large amounts of water as vapour.

8. Cold air does not hold as much moisture. As air cools, any moisture within it condenses.


How they form

Starts with a warm sea (greater than 26' to a depth of 60m) This is where hurricane gets energy as a huge quantity of water is evaporated quickly.

Not to close to the equator ( 5-15' N or S) This means that the coreolis force will cause the spiralling winds to occur.

Winds blow at the same speed from 0-12 km above sea level, otherwise hurricane wont form.

Warm, moist air rises and condenses- forming clouds that release latent heat.

More warm, moist air is drawn in, clouds continue to grow an storm intensifies.

The air rises rapidly in an upwards spiral, causing high winds.

Thick clouds produce heavy rain.

Cooler, denser air sinks, forming the eye. Inside eye conditions are calm and clear.

On either side of the eye is a towering wal of clouds called the eye wall ( up to 9 miles high). Here winds are at their strongest and heaviest rain occurs.

When formed, the hurrican is carried across the ocean by the prevailing winds generally from east to west.

When the hurricane reaches land it rapidly decreases in strength, because the source of heat, energy and moisture has disappeared and their movement slows due to friction. If hurricanes move into higher latitudes the water is cooler and they loose energy.


hurricanes are the worlds most violent an destructive storms, and a major climate hazard.     They bring with them a range of problems:

Strong winds (up to 250km/h), which destroy homes and buisnesses, and disrupt transport and power.

Storm surges, which are rapid rises in sea level, caused by low pressure and strong winds.

Torrential rain. Flooding and land slides, caused by the rain.

Average life span of a hurricane is 7-14 days.

Climate change and tropical storms

The IPCC ( intergovernmental panel for climate change) predict:

An increase in average global temperatures by the end of the 21st century of between 1.8' and 4'c.

That sea levels will rise by 28-43cm, due to polar ice melting. Some experts predict a sea level rise of up to…


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