The Major Spheres Of The Earth, Characteristics, importance

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Table of Contents

At the end you will learn the following in this article:

The earth structure
The major spheres of the Earth.
Relationship within and between the four spheres.
The structure of the Earth
Revision Questions.

Introduction

The structure of the Earth is grouped into two zones. These are the outer structure and the internal structure.

The Major Spheres Of The Earth

The major spheres of the Earth is made up of four spheres, These are:

Lithosphere
Hydrosphere
Atmosphere
Biosphere

1. Lithosphere

Characteristics Of Lithosphere

The lithosphere is the solid portion of the Earth.
It is the uttermost layer or zone of the earth crust.
It is made up of rocks and mineral materials.
It represent 30% of the earth surface.
It forms the land mass which is about 10 – 50km thick.
The outermost layer of the land mass is made up of loose rock materials like gravel, sand and soil.

Importance Of Lithosphere To Man

Lithosphere forms the basis of all human settlements.
All mineral resources are derived from lithosphere.
It aids transportation through construction of roads, railways and Airport.
All farming activities are carried out on lithosphere.
Most human activities like mining and trading are carried out on lithosphere.

2. Hydrosphere

Characteristics Of Hydrosphere

The hydrosphere is the liquid portion of the Earth.
It covers about 70% or ²/3 of the earth crust.
It holds water in various forms solid e.g, ice, liquid like water and as gases e.g, water vapor.
It includes all forms of fresh water like lakes, Rivers, water vapor.
It also includes ocean water which is salty.
Ocean water accounts for about 97% of the hydrosphere.

Importance Of Hydrosphere To Man

Hydrosphere provide water for domestic use, e.g. Washing, drinking and cooking.
It provides a medium of transportation. [Visit here for details on water transport]
It also provide water for industrial uses.
It provide food in form of fish and prawns to man.
It provides employment, e.g, fishermen.
It is a medium for sports e.g, swimming, diving.
It can also be used to generate electricity, e.g, hydro-electric power.
It is used in agriculture in form of rain or irrigation.
It also serves as tourist centers, e.g, rivers and beaches.

3. Atmosphere

Characteristics Of Atmosphere

The atmosphere is the gaseous portion of the Earth.
It is a layer of gases surrounding the Earth.
Over 99% lies within 30km of the earth surface.
It density decreases progressively with elevation.
It contains water in forms of vapor in lower layers.
Weather phenomenon such as cloud, rain and snow are largely confined in the atmosphere.
It contains 78% nitrogen, 21% oxygen, 0.03% carbohydrates and 0.97% rare or inert gases.

Importance Of Atmosphere To Man

The atmosphere is the habitat of some living organisms.
It provides oxygen for animals and plants for respiration.
It provides carbon dioxide for photosynthesis by plants.
It provide oxygen for combustion or burning.
It provides nitrogen for plants (protein synthesis).
It acts as green house.
Atmosphere is a medium of communication, e.g, air routes.
It contains ozone layer which act as protective cover for living organisms against the Burning effect of ultra-violet rays of the sun.

4. Biosphere

Characteristics Of Biosphere

The biosphere is the ozone layer of the Earth occupied by living organisms.
It is a layer of life which exist on earth surface and the lithosphere.
It has a maximum thickness of only a few kilometers.
It is a narrow zone where complex biological and chemical activities occur.
It includes organisms like plants, animals and micro-organisms.

Importance Of Biosphere To Man

Plants in the biosphere provide food for man.
They also provide a source of energy like firewood for man.
Plant also provide clothing materials like cotton and wool for man.
It provides shelter in form of timber for man.
It provides raw materials like timber, hides and skin, cotton for Industries.
Activities within the biosphere provide employment for man.
It aids the balancing and purification of atmospheric gases, e.g, carbon dioxide during respiration and oxygen during photosynthesis.

Relationship Within And Between The Four Spheres

1. Within the lithosphere

The rocks weather to form the soil.
The rocks also change to minerals like coal, petroleum and gold.

2. Within the Hydrosphere

Water from seas and oceans evaporate to form cloud and rainfall.
Water from Rivers, streams and rainfall combined to form the water in seas and oceans.

3. Within the Atmosphere

Water vapor combines to form cloud and rain.
Oxygen is taken in by plants and animals to release carbon dioxide.
Carbon dioxide is taken in by plants to release oxygen.

4. Within the Biosphere

Animals depend on plant for their food
The decomposition of animals provide manure for plants.
Micro-organisms in the soil promote plants growth.
Animals provide carbon dioxide for plants during respiration.
Plant provide oxygen for animals during photosynthesis.

Interaction Within The Four Zones

Plant and animals can be found in lithosphere, atmosphere and hydrosphere.
Plants in biosphere derive their nutrient from the soil (lithosphere).
Most human activities are mainly carried out on lithosphere.
Gases like oxygen and carbon dioxide are made constant in the atmosphere through respiration and photosynthesis.
Sunlight from the atmosphere is required by plants to carry out photosynthesis.
Atmosphere contains water vapor from the hydrosphere.

The Structure Of The Earth

The internal or inner structure of the earth is made up of three concentric layers which are:

Crust (Lithosphere)
Mantle (Mesosphere)
Core (Barysphere)

1. The Crust Or Lithosphere Characteristics

The crust is sub-divided into upper and lower parts.
The upper part of the earth crust consists of granite rocks and forms the continent.
The main mineralsl here are silica and aluminum, collectively referred to as sial.
The upper earth crust has average density of 27.
The lower part of the earth crust consists of basalt rocks and forms the Ocean floor.
It contains minerals like silica, iron and magnesium, collectively referred to as sima.
The lower crust has a density of 3.0
The sial, therefore, is lighter than the sima.
The sial and sima are 5 – 6km below the ocean and 48km below the surface of the Continent.
The lithosphere lies above the mantle.
It forms the soil and contains life.

2. The Mantle Or Mesosphere Characteristics

The mantle is found just beneath the crust.
It is about 290km thick.
It is very dense.
Its main mineral is olivine.
It is plastic and in semi-liquid form.
Has average density of about 3.3.
It is a middle layer which surround the core.

3. The Core Or Barysphere Characteristics

The core is the innermost part of the Earth.
It is about 3,476km in radius or width all round.
It contains two minerals – iron and nickel collectively referred to as nife.
The temperature of the core is estimated to be as high as 2000°C (3, 500°F).
The core is also subjected to constant temperature and pressure.
It is in molten state. The correct arrangement of the layers of the earth crust from the surface to the interior is sial, sima, mantle and core.

Revision Questions

State the major spheres of the Earth.
(a) Name the zones in the outer structure of the Earth. (b) briefly discuss the importance of two of the zones.
(a) Name the main sources of water in the hydrosphere (b) list five importance of the hydrosphere to man.
(a) Briefly describe the interaction within each zone of the outer part of the Earth (b) list four possible interactions between the four zones.
(a) Describe the main characteristics of each of the following: atmosphere, hydrosphere, biosphere (b) Highlight the importance of the atmosphere to living organisms.

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