GEOGRAPHY

• Study of the earth as the home of people(Yi-Fu Tuan, 1991)

• Study of variations in phenomena from place to place(Holt-Jensen, 1980)

Definitions

• 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

Types of Geography

Factors influence, determine and condition the distribution and activities of man

• Physical features

• Climate

• Vegetation

• Animal life

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.

Size and shape of the 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

Physical features of earth

• Rotation

• Revolution

Movements of Earth

• 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 rotation

• 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

Effects of earth’s revolution

• 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

STRUCTURE OF THE EARTH

• 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

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

Differences between continental crust and oceanic crust

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