EARTH AS HOME OF MAN.

1. FOR TRUTH AND SERVICE
Lagos State University
Centre for General Nigerian
Studies
GNS 301:Philosophy & Science
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2. Earth as home of
Man (Part 2)
DR ALAFIA, A.O.
DEPARTMENT OF ZOOLOGY AND ENVIRONMENTAL BIOLOGY
LAGOS STATE UNIVERSITY, OJO.
azeezat.alafia@lasu.edu.ng
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3. Content
1. Earths Structure
Lithosphere
Tectonic plates
Atmosphere
Hydrosphere
Fresh Water
Estuarine
Marine/Ocean Water
Biosphere
2. Earths Unique features
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4. Earth’s Structure
 The interior structure of the Earth is
layered in spherical shells, like an
onion. These layers can be defined by
their chemical and their rheological
properties.
 Earth has an outer silicate solid crust,
a highly viscous mantle, a liquid outer
core that is much less viscous than the
mantle, and a solid inner core.
 Studies have shown that there are
stable hydrous water bearing minerals
1000km deep in the earth
 and it holds over three times the
water of the oceans,
 Temperature at the centre of the core
can be as high as 7500k, hotter than
the surface of the sun
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5. Earths Structure
 Unlike the other terrestrial planets, Earths crust is divided into several
solid plates which float around independently on top of the hot mantle
below..
 This divisions are known as Tectonic plates.
 Plates can either spread (move away from one another ) or subdue
(collide and the edge of one dives beneath the other and ends up
being destroyed by the mantle.
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6. Lithosphere
 Includes all the solid materials of earth, stone, rock, soil.
 The plates move in relation to one another at one of three types of plate boundaries
 Covergent – at which two plates come together
 Divergent at which two plates pulled apart
 Transform at which two plate slide past one another
 Along the plate boundaries, earthquakes, volcanic eruptions can occur
 It is divided into several rigid TECTONIC PLATES such as
 South American plate
 Antarctic plate
 Eurasian plate
 African plate
 India-Australian plate
 Pacific
 North American
The plates ride on top of the asthenosphere
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7. Atmosphere
 Earth is enclosed by a thin shell of gas called the atmosphere
 The Atmosphere includes all the gases above the earth to the beginning of inter
planetary space.
 It is held tightly to the earths surface by gravitational force.
 It can be divided into five strata
 Troposphere - 6-10miles. with 78% N, 21% O with other inert gases
 Stratosphere- 25miles, temperature increases with increasing altitude. The
Ozone O3 is found in this region.
 Mesosphere- 40 miles(65km) decrease I temperature with increasing altitude.
 Thermosphere- 300 miles (480km) , decrease in temperature with increasing
altitude
 Exosphere –beyond atmosphere. Air is of low density.
 Ionosphere- outermost layer where molecules and atoms are ionized positively
or negatively.
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8. Hydrosphere
 Water covers about 71% of the earths surface area,
 with 99% as ocean (polar ice-caps and glaciers), high Salinity
 0.009% as freshwater, low salinity
 0.0001% as lakes and rivers.
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9. Biosphere
 A planets life forms make up its biosphere.
 Earths biosphere is believed to have evolved about 3.5bya.
 The biosphere is divided into biomes which is inhabited by plants and
animals.
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10. Earths unique features
 Densest major body in the Solar System
 Ocean – water covers 70 percent of the earth’s surface
 Earth has a moon to stabilize the planets natural wobble
 It has liquid at the surface
 Right distance from the sun
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11.  Thank you for listening
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