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Transcript 
GEOGRAPHY
Definitions
• Study of the earth as the home of people(Yi-Fu Tuan, 1991)
• Study of variations in phenomena from place to place(HoltJensen, 1980)
Types of Geography
• Physical Geography-study of physical features of the
earth
• Human Geography-studies the man-made features of the
earth
• Passive or static human geography-deals with the action
of nature upon man
• Active or dynamic human geography-deals with reaction
or action of man upon nature
Factors influence, determine and condition the
distribution and activities of man
• Physical features
• Climate
• Vegetation
• Animal life
Size and shape of the earth
Evidences
1.Edge of shadow of the earth on the moon during eclipse.
2.Possibility of cirum-navigation.
3.The horizon appearing as a clear marked circle.
Physical features of earth
Physical features of earth
Physical features of earth
• Oblate spheroid or ellipsoid shape
• Polar radius-3950 miles, equatorial radius-3963 miles
• Diameter-7926 miles-equator, 7900 mile-poles
• Polar cirucumference-24,818 miles
• Equatorial circumference-24,860miles
Movements of Earth
• Rotation
• Revolution
Effects of earth’s rotation
• Formation of day and night
• Formation of sunset and sunrise
• Getting sense of time
• Moving body experiences coriolis
force
• Caused bulge at equator flattened at
poles
• Siderial day-earth takes 23h, 56min, 4.09 sec for one rotation
Effects of earth’s revolution
• Unequal length of the day and night
• Formation of seasons
• Tropical year-earth takes 365d, 5h, 48min and 45 sec for one
revolution around the sun
STRUCTURE OF THE EARTH
• Inner core-radius-1070km, solid, very dense,
magnetized, rich in iron and nickel, 5000°C
• Outer core-4000°C, liquid –iron & nickel
• Mantle-2835km thick, 1500-3000°C,
magnesium-iron silicates
• Crust-rigid, cold, thin-SIAL, SIMA
• Moho –boundary between the crust and the mantle
• Lithosphere-rigid layer of the crust and upper mantle
• Asthenosphere - sub region of the
mantle extending about 250km below
the lithosphere
Differences between continental crust and oceanic crust
Continental crust
Oceanic crust
Average thickness-35km
Average thickness-11km including
overlying water
Main rock type-granite
Main rock type-gabbro
Density -2.8g/cm³
Density-3.0g/cm³
Thank you
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