Structure of the Earth

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

1. The layer of the earth covered with water is called…….
2. 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

1. State the four zones of the outer structure of the earth.
2. State three importance of atmosphere to man.

GENERAL EVALUATION

1. Describe the structure of the earth.
2. Explain the importance of biosphere to man.
3. State four importance of hydrosphere.
4. Mention three importance of atmosphere.
5. List three gases that can be found in the atmosphere.

READING ASSIGNMENT

Essential Geography, O.A. Iwena, Pages 21-24.

WEEKEND ASSIGNMENT

1. The part of the earth where living things are found is known as _______.

(a) hydrosphere (b) atmosphere   (c) biosphere

2. The percentage composition of oxygen in the Atmosphere is ________.
   1. 78% (b) 21%  (c) 23%
3. Which of the following minerals is found in the upper lithosphere?
   1. Olivine (b) Magnesium (c) Aluminium
4. Human beings live in which area?
   1. Atmosphere (b) Hydrosphere (c) Lithosphere
5. The part of the earth occupied by water is called _______.
   1. biosphere (b) atmosphere (c) hydrosphere

THEORY

1. Draw the inner structure of the earth.
2. State two importance of hydrosphere and atmosphere.