(a) (i) Draw a well labelled… | Geography

Question 1 Report

(a) (i) Draw a well labelled diagram to show the internal structure of the earth
(ii) Describe the distinguishing characteristics of any one of the layers shown in your diagram

(b) Outline the importance of either the hydrosphere or the biosphere to man

Answer

(a)(i) Well labelled diagram of the internal structure of the earth

The earth is made up of a series of concentric layers. Working from the outside inwards these are the crust, the mantle, the outer core and the inner core, separated by the Mohorovičić discontinuity (Moho) between crust and mantle and the Gutenberg discontinuity between mantle and core.

Labelled cross-section of the earth showing the crust, mantle, outer core and inner core, with the Moho and Gutenberg discontinuities.

(a)(ii) Distinguishing characteristics of one layer (the crust)

Taking the crust (the outermost layer shown in the diagram) as the chosen layer, its distinguishing characteristics are:

It is the thinnest and outermost layer, about 6–10 km thick beneath the oceans and up to about 35–70 km thick beneath the continents.
Its upper (continental) part forms the continents. It is built mainly of granite and is rich in silica and aluminium, so it is called SIAL. It is the lighter part, with a density of about 2.7 g/cm³.
Its lower part forms the ocean floor. It is built mainly of basalt and is rich in silica, iron and magnesium, so it is called SIMA. It is denser, with a density of about 3.0 g/cm³.
It is solid rock and is the layer on which we live, containing the soil, rocks and mineral resources.
It has the lowest temperature and density of all the layers, and it rests on the mantle at the Moho discontinuity.

(b) Importance of the hydrosphere to man

The hydrosphere is the total mass of water on, under and above the surface of the earth (oceans, seas, rivers, lakes, groundwater and water vapour). Its importance to man includes:

It provides fresh water for drinking, domestic use, irrigation of farmland and for industrial processes.
Oceans, seas, rivers and lakes serve as cheap routes for water transportation of people and goods.
It is a source of food such as fish and other sea foods, and of minerals like salt and petroleum.
Fast-flowing and dammed water is used to generate hydro-electric power (H.E.P.).
It regulates climate and drives the water cycle that brings rainfall to the land.
Water bodies are used for recreation, tourism and fishing, which provide employment and income.

Read lesson note on Hydrosphere* (WAEC)

Read lesson note on Physical Geography (JAMB)

Answer Details

(a)(i) Well labelled diagram of the internal structure of the earth

(a)(ii) Distinguishing characteristics of one layer (the crust)

Taking the crust (the outermost layer shown in the diagram) as the chosen layer, its distinguishing characteristics are:

It is the thinnest and outermost layer, about 6–10 km thick beneath the oceans and up to about 35–70 km thick beneath the continents.
Its upper (continental) part forms the continents. It is built mainly of granite and is rich in silica and aluminium, so it is called SIAL. It is the lighter part, with a density of about 2.7 g/cm³.
Its lower part forms the ocean floor. It is built mainly of basalt and is rich in silica, iron and magnesium, so it is called SIMA. It is denser, with a density of about 3.0 g/cm³.
It is solid rock and is the layer on which we live, containing the soil, rocks and mineral resources.
It has the lowest temperature and density of all the layers, and it rests on the mantle at the Moho discontinuity.

(b) Importance of the hydrosphere to man

The hydrosphere is the total mass of water on, under and above the surface of the earth (oceans, seas, rivers, lakes, groundwater and water vapour). Its importance to man includes:

It provides fresh water for drinking, domestic use, irrigation of farmland and for industrial processes.
Oceans, seas, rivers and lakes serve as cheap routes for water transportation of people and goods.
It is a source of food such as fish and other sea foods, and of minerals like salt and petroleum.
Fast-flowing and dammed water is used to generate hydro-electric power (H.E.P.).
It regulates climate and drives the water cycle that brings rainfall to the land.
Water bodies are used for recreation, tourism and fishing, which provide employment and income.