ROCKS DEFINITION AND TYPES OF ROCKS.

WEEK 9 & 10                                                                                DATE………………

SUBJECT: GEOGRAPHY

CLASS: SS 1   

TOPIC: Rocks

CONTENT: 

1. Meaning of rock and types of rocks. 
2. Mode of formation of rock types.
3. Characteristics of rock types.
4. Importance of rocks to man.

Sub – Topic 1: Definition and types of rocks.

Definition of Rock   

A rock is any solid substance that forms part of the earth crust. This solid substance may be hard, like granite or even be soft like mud. In other word, rocks are aggregates of minerals, that is, a combination of different minerals. 

The most common rocks and their minerals include;

ROCKS	MINERALS
Limestone	quart, feldspar, micas
Sandstone	quart, calcite, feldspar
Granite	feldspar, augite

Types of Rock

There are three major types of rocks according to their origin, mode of formation and physical appearance. They are

1. IGNEOUS ROCKS

Mode of formation:

These rocks are formed from the cooling and solidification of molten rock or magma from the earth beneath. They are crystalline in nature examples are Basalt and Granite. 

Igneous rock could be divided into two, namely: Intrusive or plutonic igneous rock and Extrusive or Volcanic Igneous rock

Intrusive Igneous rocks are rocks which solidified deep in the crust and they are only seen on the surface after a prolong erosive action. Examples are granite, diorite and gabbro.

Extrusive Igneous rocks are rocks that formed when the molten rock or magma are ejected and poured on the earth’s surface as Lavas. These rocks do not contain fossils. Example is Basaltic rock and they can be located in North Eastern part of Nigeria.

CHARACTERISTICS OF IGNEOUS ROCKS

1. These rocks are crystalline in nature
2. They are non- stratified rocks i.e. they do not occur in layers.
3. They are resistant to erosion and are usually hard and impervious.
4. They do not contain fossils.

SEDIMENTARY ROCKS

Mode of formation:

These rocks are formed from the accumulation of sediments either by water, ice or wind. They are derived from other pre- existing rocks such as igneous rocks. They are laid in layers or strata. These rocks are said to be stratified rocks only when they become harder in nature by compressional forces. All sedimentary rocks are non crystalline and contain fossils.

There are three major types of sedimentary rocks namely:

1. Mechanically formed sedimentary rocks. 

These rocks are formed by breakdown or disintegration of pre- existing rocks during the process of mechanical weathering. The materials are now transported by agents of erosion such as water, wind and glacier .The rock debris are then deposited either in the sea or on land .The following rocks are the result of the action of water which include clays, gravel and aluminium. Those that result from the action of ice are moraine, boulder and gravel. The only rock produce by wind is loess.

• Organically formed sedimentary rocks.

These rocks are formed from the accumulation of the remains of dead plants and animals. Some of the notable rocks formed by the remains of animals are chalk and corals and they are known as calcareous rocks. Those that result from plants include peat, coal and lignite and they are known as carbonaceous rocks.

• Chemically formed sedimentary rocks. 

These rocks are chemically precipitated from other rock solution before they solidified. Examples include potash, sodium chloride (common salt), nitrate, gypsum and dolomite.

CHARACTERISTICS OF SEDIMENTARY ROCKS

1. They occur in layers or strata.
2. The rocks may be coarse, fine soft or hard.
3. They do not exist in crystals i.e. they are non- crystalline in nature.
4. They contain fossil of plants and animals.
5. They are not resistant to erosion.

METAMORPHIC ROCKS

Mode of formation:

These are rocks whose structures and appearance have been affected by great heat and pressure. The rocks are formed from pre- existing igneous or sedimentary rocks which have been changed over time. Examples of metamorphic rocks include slate, marble, quartzite, gneiss, schist and graphite. Metamorphic regions are often regions of great economic value e.g. the Canadian shield of North America.

All rocks are subject to metamorphism. Even metamorphic rocks can still be metamorphosed. Below is a documentation of the changes some rocks undergo as a result of metamorphism.

Limestone    ==       changes to       ==    marble

Clay        ==    changes to    ==    slate

Sandstone    ==    changes to    ==    quartzite

Granite        ==    changes to    ==    gneiss

Shale        ==    changes to    ==    schist

Coal        ==    changes to    ==    graphite

The following are the three types of metamorphism: 

1. Dynamic, which is the result of pressure force from the surrounding and overlying rocks.
2. Thermal, which is caused by heat force deep beneath the earth’s surface.

III. Thermo-dynamic, which is caused by the combination of heat and pressure.

CHARACTERISTICS OF METAMORPHIC ROCKS

1. Some may occur in layers or strata.
2. The rock may be hard or soft.
3. They are not crystalline in nature.
4. They exist in different colour and texture.
5. They may contain fossil.

 

1. What is the primary component of rocks?

A. Minerals

B. Igneous rock

C. Magma

D. Sedimentary rock

2. Which of the following is NOT a type of rock?

A. Metamorphic

B. Cambrian

C. Porphyritic

D. Amphibolite

3. Which of the following is NOT a characteristic of metamorphic rocks?

A. Increased density

B. Melted and recrystallized minerals

C. Change in texture

D. Original rock composition remains the same

4. What is the main difference between igneous and sedimentary rocks?

A. Igneous rocks are formed from solidified lava or magma, while sedimentary rocks are formed from weathered debris

B. Igneous rocks are found on the Earth’s surface, while sedimentary rocks are found below the surface

C. Sedimentary rocks are older than igneous rocks

D. Igneous rocks are made up of smaller particles than sedimentary rocks

5. Which of the following is NOT a type of igneous rock?

A. Gabbro

B. Diorite

C. Shale

D. Andesite

6. Which of the following is a type of sedimentary rock?

A. Coal

B. Limestone

C. Diorite

D. Gneiss

7. Which of the following is NOT a characteristic of sedimentary rocks?

A. Layered

B. Composed of smaller particles than igneous rocks

C. Formed from solidified lava or magma

D. May contain fossils

8. Which of the following is NOT a type of metamorphic rock?

A. Gneiss

B. Schist

C. Slate

D. Hornfels

9. What is the main difference between magma and lava?

A. Lava is found on the Earth’s surface, while magma is found below the surface

B. Magma is molten rock that has not yet solidified, while lava is solidified magma

C. Lava is hotter than magma

D. Magma is more dense than lava

10. What is the difference between an intrusive and an extrusive igneous rock?

A. Intrusive igneous rocks are found below the Earth’s surface, while extrusive igneous rocks are found on the surface

B. Extrusive igneous rocks solidify more quickly than intrusive igneous rocks

C. Intrusive igneous rocks have a lower silica content than extrusive igneous rocks

D. Extrusive igneous rocks have a lower silica content than intrusive igneous rocks

Marking Guide

1. A

2. B

3. D

4. A

5. C

6. A,B

7. C

8. D

9. B

10. B

 

 

EVALUATION: 

1. Outline four major differences between sedimentary and metamorphic rocks
2. Describe the characteristics and mode of formation of igneous rocks.

Sub-Topic 2:

ECONOMIC IMPORTANCE OF ROCKS TO MAN

1. Sources of Minerals: some rocks are sources of minerals such as gold, diamond, limestone, petroleum etc. Which can be exported to provide foreign exchange to a country.Petroleum coal, limestone are derived from sedimentary rocks while gold, diamond and tin are derived from igneous and metamorphic rocks.
2. Sources of Fuel: sedimentary rocks like petroleum and coal are sources of fuel for domestic and industrial uses.
3. Construction Purposes: some rocks like granite and sand stone are quarried and used for roads, bridges and building construction.
4. Tourist Centres: Huge rock masses on mountain serve as tourist centres e.g. Olumo rock in Abeokuta and Zuma rock in Suleja.
5. As Ornamental: Some beautiful rocks such as marble can be polished as ornaments for decorating floors, walls of building, churches, tombstones etc.
6. Sources of food Nutrients: Rock salts as sodium chloride (table salt) from sedimentary rocks provide minerals used in cooking.
7. Formation of Soil: soil are formed from the disintegration of rocks.
8. Sources of Metal: Rocks are sources of metals which are derived from mines e.g. gold, silver, iron, aluminium, copper etc.
9. Domestic uses: some rocks like granite are used for domestic purposes e.g. grinding stones.
10. Raw Materials for Industries: some sedimentary rocks are used as raw materials in industries e.g. limestone is used for making cement, dolomite and marble are used for manufacturing of glasses and house paints.

EVALUATION 

Highlight five importance of metamorphic rock to man

GENERAL EVALUATION:

1. (a) Define the term sedimentary rock and describe any two process of its formation                       (b) Discuss any three ways in which sedimentary rocks are important to man (SSCE November 1992).
2. (a) Name the three classes of sedimentary rocks to man (b) Explain with examples: the process of formation of the three classes of sedimentary rocks. (c) State four uses of rocks to man (WASSCE November 1999).
3. (a) Give two examples each of sedimentary and metamorphic rocks (b) Outline four major differences between sedimentary and metamorphic rocks. (WASSCE June 2000).
4. (a) What are sedimentary rocks? (b) Name the three classes of sedimentary rocks according to their mode of formation. (c) Describe one of the classes of sedimentary rocks in (b) above. (d) Outline four ways in which sedimentary rocks are important to man.
5. Mention five characteristics/features that differentiate one rock from the other.
6. Discuss rocks under the following headings: (i) Structure (ii) Colour (iii) Texture                       (iv) Permeability.  

WEEKEND ASSIGNMENT

Objective Test:

1. Which of the following rocks is sedimentary? (A) Coal (B) Gneiss (C) Granite (D) Marble 
2. Granitic rocks contain (A) silica and aluminium. (B) silica and iron. (C) magnesium and copper. (D) copper and bauxite. 
3. Which of the following is a characteristic of igneous rock? (A) Loose in composition                     (B) Arranged in layers                       (C) Crystalline in nature (D) Porous in granular structure.
4. Which rock type involves stratification? (A) Metamorphic (B) Sedimentary    (C) Volcanic (D) Igneous.
5. Which of the following statements is not correct? (a) Igneous rocks do not contain fossils                 (b) rocks that are changed by great heat and pressure are called sedimentary rocks (c) Basalt and granite are examples of igneous rock (d) marble and gneiss are examples of metamorphic rock (e) Rocks that are formed through the extrusion of molten magma are called volcanic rocks.

Essay Questions:

Discuss the mode of formation and characteristics of any type of rock.

ECONOMIC IMPORTANCE OF ROCKS TO MAN

1. Sources of Minerals: some rocks are sources of minerals such as gold, diamond, limestone, petroleum etc. Which can be exported to provide foreign exchange to a country.Petroleum coal, limestone are derived from sedimentary rocks while gold, diamond and tin are derived from igneous and metamorphic rocks.Minerals are natural resources which can be found in rocks. Some of these minerals are valuable, and they can be used to generate foreign exchange for a country. Rocks containing petroleum, coal, and limestone are sedimentary rocks, while those containing gold, diamond, and tin are igneous or metamorphic rocks.In generally , rocks provide a variety of materials that are essential for the functioning of modern society. These materials include aggregate for construction, road building, and making concrete; ores for metals such as iron, aluminum, and copper; dimension stone for buildings and monuments; decorative stone for landscaping; and a variety of other uses.There are three major
2. Sources of Fuel: sedimentary rocks like petroleum and coal are sources of fuel for domestic and industrial uses.Building Materials: rocks are used as building materials, such as stone, bricks, and concrete.Landscaping: rocks can be used for landscaping purposes, such as to create rock gardens or to line walkways.Other Uses: rocks can also be used for a variety of other purposes, such as in the production of glass or as a source of gemstones.Rocks are an important part of the Earth’s crust and can be found in a variety of settings, from mountains to deserts. While most people think of rocks as being simply things that we see in our everyday lives, they actually have a number of important uses.For example, rocks are a major source of fuel for both domestic and industrial purposes. In addition, rocks are used to make a variety of building materials, such as stone, bricks, and concrete. Rocks can also be used for landscaping purposes, such as to create rock gardens or to line walkways. Finally, rocks can also be used for a variety of other purposes, such as in the production of glass or as a source of gemstones.While rocks may not seem like they have a lot of uses, they actually play a vital role in our everyday lives. Next time you see a rock, take a moment to think about all of the ways that it benefits us!
3. Construction Purposes: some rocks like granite and sand stone are quarried and used for roads, bridges and building construction.
4. Tourist Centres: Huge rock masses on mountain serve as tourist centres e.g. Olumo rock in Abeokuta and Zuma rock in Suleja.Soil Conservation: huge rock masses help to conserve the soil by reducing surface run off, preventing gully erosion and retaining moisture.Defence Purposes: in war times, rocks can be used as barricades.Rocks are an important part of the Earth’s crust and can be found in a variety of settings, from mountains to deserts. While most people think of rocks as being simply things that we see in our everyday lives, they actually have a number of important uses.For example, rocks are a major source of fuel for both domestic and industrial purposes. In addition, rocks are used to make a variety of building materials, such as stone, bricks, and concrete.
5. As Ornamental: Some beautiful rocks such as marble can be polished as ornaments for decorating floors, walls of building, churches, tombstones etc.
6. Sources of food Nutrients: Rock salts as sodium chloride (table salt) from sedimentary rocks provide minerals used in cooking.
7. Formation of Soil: soil are formed from the disintegration of rocks.
8. Sources of Metal: Rocks are sources of metals which are derived from mines e.g. gold, silver, iron, aluminium, copper etc.
9. Domestic uses: some rocks like granite are used for domestic purposes e.g. grinding stones.
10. Raw Materials for Industries: some sedimentary rocks are used as raw materials in industries e.g. limestone is used for making cement, dolomite and marble are used for manufacturing of glasses and house paints.

Write ten multiple-choice questions with one correct answer and three wrong answers on the topic of the economic importance of rocks to man

1. What is the primary use of rocks?

A. To provide fuel for domestic and industrial purposes

B. To serve as tourist centres

C. To create rock gardens

D. To produce gemstones

2. What are some of the ways that rocks can be used for construction purposes?

A. To make stone and bricks

B. To line walkways

C. To create rock gardens

D. To provide a source of gemstones

3. What is the role of rocks in soil conservation?

A. They help to reduce surface run off

B. They prevent gully erosion

C. They help to retain moisture

D. All of the above

4. What is one use of rocks that is not commonly thought of?

A. To make glass

B. As a source of gemstones

C. To provide fuel for domestic and industrial purposes

D. As a barricade

5. What is the economic importance of rocks to man?

A. They are a vital part of the Earth’s crust

B. They provide a number of important uses

C. They play a role in our everyday lives

D. All of the above

6. What are some of the ways that rocks can be used for landscaping purposes?

A. To create rock gardens

B. To line walkways

C. To provide a source of gemstones

D. All of the above

7. What is the role of rocks in the formation of soil?

 

A. They help to reduce surface run off

B. They prevent gully erosion

C. They provide nutrients for plants

D. All of the above

8. What is the primary use of rocks in industry?

A. To provide fuel for domestic and industrial purposes

B. To serve as a raw material

C. To provide a source of gemstones

D. To create rock gardens

9. What is the role of rocks in the tourist industry?

A. They help to promote tourism

B. They provide a number of important uses

C. They play a role in our everyday lives

D. All of the above

10. What is the role of rocks in the food industry?

A. They provide a source of gemstones

B. They provide a source of metals

C. They are a major source of fuel

D. They provide minerals for cooking.