The structure of the earth is grouped into two zones: The outer structure and the internal structure.
THE OUTER STRUCTURE OF THE EARTH
The outer structure of the earth is made up of four zones or layers:
- Lithosphere
- Hydrosphere
- Atmosphere
- Biosphere
- Lithosphere: This is the solid portion of the earth. It is the outermost zone of the earth which is made up of rocks and mineral materials. It represents 30% of the earth surface.
Importance:
- It forms the basis for all human settlement.
- All mineral resources are derived here.
- It aids transportation through construction of roads, railways, airports, etc.
- It aids farming activities.
- Most human activities like mining, trading, etc are done here.
- Hydrosphere: This refers to the liquid portion of the earth. It includes the oceans, sea, rivers, streams and springs, lakes, etc. It covers 70% of the earth’s crust.
Importance:
- Provides water for domestic uses.
- Provides medium for transportation.
- Provides water for industrial uses.
- Provision of food(fishes, prawns, etc)
- Provision of employment.
- Serves as tourist centre.
- Generation of hydro-electric power(HEP)
EVALUATION QUESTIONS
- The layer of the earth covered with water is called…….
- Mention any four importance of hydrosphere to man.
- Atmosphere: this is the gaseous portion of the earth. It contains 78% nitrogen, 21% oxygen, 0.03% carbon dioxide and 0.097% rare gases.
Importance:
- It is the habitat of some living organisms.
- It provides oxygen for respiration.
- It provides carbon dioxide for photosynthesis.
- It provides oxygen for combustion.
- It provides medium of transportation.
- It provides nitrogen for protein synthesis in plants.
- Biosphere: This is the zone of the earth where living things are found.
Importance:
- Plants provide food for man.
- Provision of employment.
- Provision of raw materials.
- Balancing and purification of the atmosphere.
EVALUATION QUESTIONS
- State the four zones of the outer structure of the earth.
- State three importance of atmosphere to man.
GENERAL EVALUATION
- Describe the structure of the earth.
- Explain the importance of biosphere to man.
- State four importance of hydrosphere.
- Mention three importance of atmosphere.
- List three gases that can be found in the atmosphere..
WEEKEND ASSIGNMENT
- The part of the earth where living things are found is known as _______.
(a) hydrosphere (b) atmosphere (c) biosphere
- The percentage composition of oxygen in the Atmosphere is ________.
- 78% (b) 21% (c) 23%
- Which of the following minerals is found in the upper lithosphere?
- Olivine (b) Magnesium (c) Aluminium
- Human beings live in which area?
- Atmosphere (b) Hydrosphere (c) Lithosphere
- The part of the earth occupied by water is called _______.
- biosphere (b) atmosphere (c) hydrosphere
THEORY
- Draw the inner structure of the earth.
- State two importance of hydrosphere and atmosphere.
See also
CALCULATION OF DISTANCES AND LOCAL TIME