Guide to learn all your case studies and the igcse cambridge revision guide for theories and key terms

Ridges of sand which form behind beaches.

An obstacle is formed by a plant or sand hill and this slows down the wind coming from the sea. Any and or dust that the wind is carrying is deposited around the obstacle and it grows; like a sand dune.

Plants begin to grown there and their roots stabilise the dune so it become stronger.

Over time the dune become grey as plants die and they decay leaving behind humus.

Eventually the plant life grows and the sand is able to hold more water and trees can now grow here, transforming it into part of the earth.

The solid skeleton of limestone

It grows in warm water 23-25°

Grows in clear shallow salt water

Needs plenty of sunlight

How are they formed?

Large amount of coral build up over a long period of time and get higher and higher.

They begin building from a rock base in the ocean

There are THREE different ways this can happen and therefore THREE different types of coral reef.

Case study: Coral Reef: Great Barrier reef, Australia

When we wake up in the morning one of the first things we are interested in is the weather.

* The atmosphere is the layer of gases, called air, which surrounds the planet earth.

* The air in the atmosphere is a mixture of gases. These are mainly nitrogen (about 4/5) and oxygen (about 1/5). There are also amounts of water vapour, carbon dioxide and some rare gases. The amount of water vapour is very important as this gives us our cloud and rain.

The components of the weather
To describe the weather we must describe the state of the air. We can do this under 6 main headings. These are called the elements of the weather:

1. air temperature - How hot or cold is it?

2. precipitation (rain, snow, hail, sleet, frost, fog, dew) - Is it wet or dry?

3. cloud cover and sunshine - Is it sunny or cloudy?

4. wind speed and direction -The movement of the air.

5. air pressure

 

The climate of a place is its average weather. To calculate this we must know what types of weather occur there at different times of the year.

We measure the temperature of the air in degrees Celsius (ºC) using a thermometer.

EQUIPMENT NAME	PHOTO	DESCRIPTION (WHAT DOES IT MEASURE)
Stevenson Screen		A Stevenson screen is basically a white louvered wooden box. The box is designed to contain some weather equipment like thermometers and barometers. The Stevenson screen is white to reflect sunlight and has slats to allow air to circulate easily. The Stevenson should be placed above the ground and away from the buildings. The idea is for the weather instruments to take accurate readings of the air, rather than direct sunlight or heat from the ground or from buildings. For more detailed information about the siting of a Stevenson Screen, read the attached document.
Barometer		Barometers are used to measure air pressure. Air pressure is normally measured in millibars. Barometers are normally kept inside Stevenson screens to keep them safe. A barometer has a movable needle (pointer). The pointer can be moved to the current reading so that you can then make a comparison with the reading from the following day.
Max./Min. Thermometer (sometimes called a Six's thermometer after its inventor)		A maximum and minimum thermometer records the maximum temperature of the day and the minimum temperature of the day (diurnal range). A maximum/minimum thermometer contains a mixture of mercury and alcohol. The mercury sits in the u-bend of the thermometer. The bulb at the top of the tube reading the minimum temperature contains alcohol and the bulb at the top of the tube reading the maximum temperature contains a vacuum. On the minimum side the expansion of the mercury is restricted by the contracting alcohol, on the maximum side the expanding mercury can expand more freely into the vacuum. At any given time both thermometers should record the same temperature. However, during the day they would have recorded the maximum and minimum temperature - a steel marker should indicate these temperatures.
Wet/Dry Bulb Thermometer (hygrometer)		A hygrometer measures the humidity of the air. Humidity is the amount of moisture (water vapour) in the air. A hygrometer has two thermometers, a dry one and a wet. Humidity is measured by using a table that looks at the difference between the wet bulb and the dry bulb. A hygrometer can also be used to find dew point. There is a difference between the dry and wet bulb thermometers because of latent heat created during the process of evaporation.
Rain gauge		Rain gauges are used to measure rainfall. Rainfall is normally measured in millimetres. Rain gauges should be placed on grass, because if they are placed on concrete, extra water can splash into them. Rain gauges should also be checked regularly to avoid evaporation.
Wind Vane		Wind vanes are used to check the direction of the wind. Compass points are used to give wind direction. Wind is measured in the direction that the wind is coming from. Wind vanes are often placed on top of buildings so that they are fully exposed to the wind. When using a wind vane you need to use a compass to make sure that it is properly aligned.
Anemometer		Anemometers measure wind speed. Wind speed is normally measured in mph or kph, but can also be measured in m/s (metres a second). Digital anemometers are very accurate, but the more basic plastic ones that many schools have aren't very good or accurate at recording light winds. Anemometers are normally placed on top of buildings so that they are not protected from the wind and so they don't experience channeling of wind e.g. if an anemometer was placed in a corridor where wind was forced through the readings would be higher than normal.
Cloud Cover		It is also possible to count day light hours, sunshine hours or cloud cover. To Calculate day light hours you need to record the time between sun rise and sun set. To Calculate sun shine hours is a lot harder, because you have to time every time the sun comes out (stopwatch). To calculate cloud cover a mirror is often used. You divide the mirror into squares and then place the mirror on the ground. The mirror will reflect the clouds and you can count the number of squares covered or partially covered by cloud. You can do this as a percentage or convert to oktas which is the normal measurement of cloud cover. You have to take several readings to avoid anomalous results.

The weather we get from high air pressure is very different from that we get with low air pressure

Clouds are a collection of water droplets or ice crystals. The warmer the air temperature, the more water vapour (gas) that the air can hold. However, when the air starts to cool, water vapour starts to condense as long as it has condensation nuclei to condense around.

Common throughout the world

Thin and wispy in appearance

Move fairly quickly

Low level – below 2000m and sometimes reaching ground.

Usually grey and colour and move fast.

Can produce light rain and snow.

Large clouds up to 10km high and across.

They resemble giant cauliflower.

Produce rain, thunder and lightening

Usually found in spring and summer


Cumulus

Fairly low clouds with bottom between 600m and 1200m

Look like lumps of cotton wool

Can produce light rain

Individual clouds have a short life cycle
Climate zones and graphs

Climate zones around the world depend on a variety of factors but more or less we can se they are dependent on the lines of latitude around the earth as the further away or closer we are to the equator will affect the temperature we experience.

See blow for the climate zones and the factors which can affect the climate within one country.




Climate graphs show us the climate over a year of different areas in the world.

They concentrate on rainfall and temperatures and you must be careful to be sure you can use the following terms to use terms to explain climate.

• 
  Range of temperatures
  
• 
  Maximum and minimum temperatures
  
• 
  Annual precipitation
  
• 
  Minimum and maximum precipitation
  

e.g. tropical, arid, Mediterranean

• 
  mostly found along the equator
  

• 
  Plenty of rain, over 1500 mm in some areas
  
• 
  10% of worlds rainfall depends on evaporation and transpiration from these rain forests
  
• 
  Ever green forests with broad leaved trees
  
• 
  Lots of flora and fauna (can be 40-100 tree species per hectare)
  
• 
  Large amounts of shade at low levels
  
• 
  Most plants grow up high where they can get to the light
  
• 
  Plants that reach the sky are called emergent and they can create their own islands in the canopy of the forest called the ‘lungs of the Earth’ as they produce oxygen.
  
• 
  Low pressure weather allowing clouds to form and rain occurs all year but in varying amounts.
  

• 
  The Congo Basin in central and west Africa
  
• 
  The Amazon in Brazil, Peru, Bolivia and Ecuador
  
• 
  SE Asia (Malaysia, Thailand, Vietnam, Indonesia and the Philippines)
  
• 
  Madagascar
  
• 
  North east Australia
  
• 
  Southern India and Sri Lanka
  
• 
  Central America
  

• 
  Habitat loss (deforestation)
  
• 
  Climate change (reduction in rainfall or increases in temperature)
  
• 
  Pollution (especially reptiles and amphibians)
  
• 
  Hunting (food food, skins and parts for Chinese medicine)
  
• 
  Cross breeding with domestic animals
  

• 
  Diseases (bird flu)