Geography

• Rotation of the Earth

  The Earth rotates once through 360° in 24 hours
• Rotation of the Earth

  1. It rotates 1 degree every 4 mins

  2. Causes day and night

  3. Causes deflection of wind

  4. Causes ocean currents

  5. Causes rises of tides in water bodies
• A difference of 1 hour between two meridians is 15° apart
• The sun reaches its highest position on the sky at 12:00 noon local time along the meridian
• All places on the same meridian have the same local time
• Local time at Greenwich is called Greenwich Mean Time (GMT)
• Meridians to the east of the Greenwich Meridian


  Have sunrise before the Prime Meridian, local time is ahead of GMT
• Meridians to the west of the Greenwich Meridian


  Have sunrise after the Greenwich Meridian, local time is behind GMT
• Longitude


  An imaginary line running from North to South which shows how far East or West a place is from the Prime Meridian
• Calculating time difference from GMT

  1. Find the difference in longitude between the two places

  2. If the place is East of Greenwich, add the time difference

  3. If the place is West of Greenwich, subtract the time difference
• Revolution of the Earth

  The movement of the Earth around the Sun
• The revolution of the Earth causes the changes of seasons in different parts of the Earth
• The revolution of the Earth brings about differences in temperature in different parts of the world
• The Northern Hemisphere experiences summer in June because the Sun's rays heat the Northern Hemisphere directly due to the Earth's tilt of 23.5° from the vertical line
• The Earth experiences equinox in March and September
• The Earth experiences winter solstice on December 21-22
• The Southern Hemisphere experiences summer in December due to the Earth's tilt towards the Sun
• The Northern Hemisphere experiences cooler temperatures in November-April when the Earth is tilted away from the Sun
• The Southern Hemisphere experiences cooler temperatures in May-August when the Earth is tilted away from the Sun
• Farmer's activities in different seasons

  1. Autumn: Drying of crops, tilling the garden

  2. Winter: Rest, maintenance, purchasing inputs for next season

  3. Spring: Planting crops, applying herbicides and pesticides

  4. Summer: Rest
• Barometer


  Instrument used to measure atmospheric pressure
• Hygrometer


  Instrument used to measure the amount of water vapour in the atmosphere
• Thermometer

  Instrument used to measure temperature, including maximum and minimum thermometers
• Measuring rainfall


  1. Rain water passes through a funnel into a collecting jar

  2. After 24 hrs, the water is collected and poured into a measuring cylinder to determine the amount of rainfall
• Wind vane

  • Shows the four cardinal points of the compass
  • Rotates according to the direction the wind is blowing from
• Anemometer

  • Consists of 3-4 semi-circular metal cups fixed to rotating arms
  • The faster the wind, the faster the cups rotate
  • The number of rotations is recorded to determine wind speed in km/h or knots
• Wind sock is used to indicate the general direction of wind flow, but not the accurate direction
• Latitudes


  Lines that run from 0° at the Equator to 90° north or south of the Equator
• Latitudes are lines that run from 0° at the Equator to 90° north or south of the Equator
• Longitudes


  Also called meridians, the main longitude marked 0° is called the Prime Meridian or the Greenwich Meridian
• Prime Meridian


  The main longitude marked 0°
• Longitudes are measured in degrees east or degrees west of the Prime Meridian
• All longitudes east of the Prime Meridian are measured up to 180° east, while all those west of the Prime Meridian are measured up to 180° west
• The 0° and 180 lines are not given east or west labels as the 180° line is an extension of the 0 line
• The other lines of longitude are labelled east or west of the Prime Meridian, for example, 60° W, 115° W 15° E and 175° E
• The rotation of the earth causes a difference of 1 hour in every 15° interval between longitudes
• The earth takes 24 hours to make a complete rotation of 360° of longitudes
• If you want to find out how many degrees the earth will have rotated in an hour, you divide 360° by 24 hours. This will give you 15°. This means that it takes the earth 1 hour to rotate through 15°
• Anemometer


  Instrument which measures wind speed
• Wind Vane


  • Measures the direction of the wind
  • Spins on a rod and points in the direction from which the wind blows
  • The part of the vane that turns into the wind is usually shaped like an arrow
  • The other end is wide so it will catch the smallest breeze