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1. Latitudes Longitudes
• All latitudes are concentric circles & they are parallels as
well
• Lines of latitude cross lines of longitude at right angles
• Largest latitude – equator
• Tropics – heat surplus
• Temperate, polar regions – heat deficit
• Responsible for pressure system and planetary wind system
• Angular distance of a place from prime meridian
• Also called meridians
• 00
degree = Greenwich in UK
• 1800
degree = International date line
• Earth rotates 360°s in 24 hours
o 360/24 = 15° or 1° in four minutes.
o 15° longitude = 1 hour
Two Parts of Geography
Physical Human
 Geomorphology
 Climatology
 Oceanography
 Habitation
 Population
 Agriculture
 Industries- resources

2. International Date Line (IDL)
 The Dateline Is Not Straight why?
 The dateline runs from the North Pole to the South Pole and marks the divide between the Western
and Eastern Hemisphere.
 It is not straight but zigzags to avoid political and country borders and to not cut some countries in
half.
 What Happens When You Cross the Dateline?
o When you cross the International Date Line from west to east, you subtract a day, and if you cross
the line from east to west, you add a day.
Q) If 12 noon at GMT what is the time at 75 °E?
• Difference = 75 °
• 15 ° => 1 hour
• 75 ° => 5 hours
• East (means add) 12 +5 = 5 pm
Q) If 12 noon at GMT what is the time at 30 °W?
 Difference = 30 °
 15 ° => 1 hour
 30 ° => 2 hours
 East (means minus) 12 - 2 = 10 am
Q. If it is 10.00 am IST, then what would be the local
time at Shillong on 92 deg E Longitude?
a) 9.38 am
Standard time
 Every country selects its standard meridian.
 Angular distance between standard meridian of a nation to
Greenwich meridian time (GMT)
 Indian Standard Time
o IST – 82.5 E Meridian
o IST - 5.5 hours ahead of GMT, so GMT+5.5

4. Rotation
 The Earth spins on its axis from West to East (counter-clockwise).
 The Earth moves around the sun in an elliptical orbit.
 It takes the Earth 23 hours, 56 minutes, and 4.09 seconds to complete one full turn.
 The speed of rotation at any point upon the equator is at the rate of approximately 1,038 miles per hour,
decreasing to zero at the poles.
Revolution
 While the Earth is spinning on its axis, it is revolving around the Sun in a counter-clockwise direction.
 It takes the Earth one full year to complete one full revolution around the Sun.
 The mean distance of the Earth from the Sun is about 93 million miles and the distance varies by 3 million
miles, forming a slightly oval path.
Aphelion and Perihelion of earth
 Earth is at its maximum distance from the sun at aphelion, and at its minimum distance at
perihelion.
 The point in the moon’s orbit where it is farthest from the earth is called apogee, while it’s closest
approach is known as perigee.

5. Basics – I
Climate and Weather
• Weather is what is observed on any particular day.
• Climate is an average of weather conditions, considered over a span of 30 years
Modes of heating
• Conduction takes place when two bodies of unequal temperature are in contact with one another, there is a
flow of energy from the warmer to cooler body.
• Convection is the transfer of heat through the movement of liquids and gases.
• Radiation is the transfer of energy through air and space by light waves (visible, ultraviolet and infrared
waves).
• Hotter bodies emit shortwaves radiation and cooler bodies emit longwave radiations
• The degree of hotness or coldness of any substance is measured by a parameter referred to as temperature.
• The specific heat is the amount of heat per unit mass required to raise the temperature by one degree
Celsius
• Evaporation is the process of conversion of liquid water into gaseous / vapour state under normal
atmospheric conditions.
• Condensation is the process where water vapor becomes liquid. It is the reverse of evaporation,
where liquid water becomes a vapor.
Condensation happens one of two ways: Either the air is cooled to its dew point or it becomes
so saturated with water vapor that it cannot hold any more water.

6.  Latent heat is defined as the heat or energy that is absorbed or released during a phase change of a
substance. It could either be from a gas to a liquid or liquid to solid and vice versa.
 Properties of Ice and Water
 Theanomalous expansion of water is an abnormal property of water whereby it expands instead of
contracting when the temperature goes from 4o C to 0o C, and it becomes less dense. Thedensity is
maximum at 4 degree centigrade anddecreases below that temperature as shown in graph. The density
becomes less and less as it freezes because moleculesof water normally formopen crystal structures when
in solid form.
Air Pressure

7. • The weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere
is called the atmospheric pressure.
• The atmospheric pressure is expressed in units of millibar.
• At sea level the average atmospheric pressure is 1,013.2 millibar.
• The instrument used to measure atmospheric pressure is called a barometer. The most commonly used
barometers are the mercury barometer, aneroid barometer and barographs.
• Change of pressure with height
We experience high air pressure at sea level because the whole atmosphere is pushing down on us. When
we’re on top of a mountain, there is less air pushing on us and the pressure is low.
• Isobars – Pressure
The imaginary line which join points of equal pressure is known as an isobar.
• Pressure Gradient-The rate of change of pressure with distance is is referred to as pressure gradience. Closer
the isobars, greater is the pressure gradience and vice versa.
• Relation Between Temperature and Pressure
 Warm Air - Low Pressure
 Cold Air - Higher Pressure
Solar Radiation
• It is the prime source of heating on the earth’s surface.
• The solar radiation actually reaching the Earth’s surface is quite different from the solar radiation measured
above the Earth’s atmosphere.

8. • This is because solar radiation is both absorbed and scattered by varying amounts at different wavelengths
as it passes through the atmosphere.
Heat Budget of the Planet Earth
• The earth as a whole does not accumulate or lose heat.
• It maintains its temperature.
• This happens as the amount of heat received equals the amount lost by the earth.
Terrestrial Radiation