ROCK FORMATION

Subject:

Agricultural Science

Class:

SS 1

Term:

Second Term / 2nd Term

Week:

Week 4

Topic:

ROCK FORMATION

Previous Knowledge: The pupils have previous knowledge of

 ROLES OF SCIENCE AND TECHNOLOGY IN AGRICULTURAL DEVELOPMENT

that was taught in their previous lesson.

Behavioural  Objectives : At the end of the lesson, learners will be able to

• Say the meaning of rock .
• Write out the process of rock formation
• Explain the minerals that are found in rock .
• Recognize and identify types of rock

Instructional Materials 

• Wall charts
• Online Resource
• Textbooks
• Laptop
• Flash cards
• www.edudelighttutors.com

Methods of Teaching 

• Role modelling
• Questions and Answers
• Explanation
• Discussion
• Recitation
• Imitation
• Story Telling
• Dramatization

Content: 

Meaning of Rock
Rock is defined as any mineral material of the earth. Rock can also be defined as the aggregate of minerals made up of hard and soft materials like stone, sand, etc. Rock constitutes a significant part of the earth’s crust. The earth’s crust consists of rocks which are the combination of different mineral elements such as silica which contains silicon and oxygen. Rocks are aggregates (mixtures) of minerals.

The Process of Rock Formation
Rocks are formed as a result of volcanic eruptions from earth’s crust. During the volcanic eruption the molten material or magma may remain within or escape to the surface . The magma or lava subsequently cools and solidifies to form glassy crystalline textured mass. In Nigeria rocks are found in Benue, Bauchi, Zaria, Plateau, Ilorin, Ondo, Ado-Ekiti, Abakiliki and Ogoja in Cross River State, etc.
Some of the magma may cool before reaching the surface of the earth thus forming plutonic rocks (intrusive rocks) while some may reach the surface to form volcanic rocks (extrusive rocks)
Examples of plutonic (intrusive) rocks are granite, diorite, gabbro, etc.
Examples of volcanic (extrusive) rocks are basalt, andesite, obsidian, pumice, rhyolite, scoria and tuff. Rapid cooling gives rise to fine grained rocks,while slow cooling gives rise to larger grained rocks.

Rock Minerals

Rock contains primary and secondary minerals, namely;

The Primary Rock Minerals that exist in the natural form consist of quartz, biotite, olivine, magnesium,iron, and aluminium, sulphate and carbonate of iron, magnesium and calcium, clay minerals such as the silicate and hydrous oxide.

Secondary Rock Minerals are: (a) Oxides of metal e.g. sodium oxide (Na₂O).(b) Mortmorilonite.

Types of Rock
Rocks are grouped according to their mode of formation, appearance and minerals composition. Based on this analysis, there are three types of rock. They are as follows:

Igneous rock Sedimentary rock

Metamorphic rock Igneous Rock

This is formed as a result of high temperature and pressure beneath the earth’s crust which causes the liquid material (molten magma) below the earth surface to solidify or erupt in the form of a volcano. There are two types of igneous rock;

Intrusive or plutonic Extrusive or volcanic
Examples of igneous rock rocks include: granite, diorite, gabbro, (they contain minerals like quart, feldspar, and mica) – plutonic, while basalt and andesite are extrusive.

Rock Formation – Igneous rockIgneous Rock

• Characteristics of Igneous Rocks
  Igneous rocks generally have the following features:
• They are coarsely crystalline in nature.
• They are glassy in appearance.
• Igneous rocks are usually hard and impervious.
• They are resistant to erosion and other elements of climate
• They do not contain fossils.
• Their colours vary from pink, green, grey, or black.
• They do not form layers i.e. they are non-stratified rocks

Sedimentary Rocks
Sedimentary rocks are formed when weathered particles are carried from their place of origin and deposited in another area as solid particles or when the pre-existing rocks are broken down
by geological denudation agents.The materials carried are usually laid down in
strata/sediments/layers.They are usually cemented together by organic matter,cemented agents or pressure.

Example of sedimentary rocks are
limestone,sandstone,coal,dolomite,clay,shale,mudstone,peat,lignit,and gypsum.
Types of Sedimentary Rock
There are three types of sedimentary rocks; they are

Mechanically formed sedimentary rocks

Organically formed sedimentary rocks

Chemically formed sedimentary rocks

Mechanically Formed Sedimentary Rocks

Mechanically formed sedimentary rocks are known as secondary rocks.They are formed as a result of accumulation and cementation of weathered materials over a period of time.e.gs are
dolomite,conglomerates,sandstone,limestone and quarzites.

Organically Formed Sedimentary Rocks
Organically formed sedimentary rocks are formed as a result of deposition and hardening shell
sand skeleton of aquatic organisms such as fish, oyster shells and snails. Examples are coal, peat, graphite and lignit. The remains of plants and animals found in sedimentary rocks are known as fossils.

Chemically Formed Sedimentary Rocks
They are formed as a result of chemical reaction of minerals in the rocks, precipitates are formed and deposited in layers over time .e.g sodium chloride, gypsum and nitrate.

• Rock Formation – Sedimentary rock
  Sedimentary Rock
  Characteristics of Sedimentary Rocks
• They occur in layers(stratified).
• They contain fossils (dead plants and animals).
• They are prone to erosion.
• They formed precipitates.They react with weak acids.
• They are soft.

Metamorphic Rocks
These are derived from pre-existing sedimentary or igneous rocks by the agents of metamorphism such as heat, pressure and chemical change.
Examples include: gneiss, schist, quartzite, marble, slate. Rock Formation –

Metamorphic rock

Importance of Rocks In Agriculture

For soil formation.
Plants nutrients which are utilized by plants are derived from rocks. Examples are Magnesium, calcium,manganese,silicon,sodium and Potassium.

For road construction and farm building. Other Uses of Rocks Other uses of rocks include:

Domestic use – as grinding stone. Source of metals – granite, silver, copper, diamond, etc. Source of fuel – petroleum and coal As ornamentals Exportation

As raw materials (e.g. limestone, dolomite, marble) for our industries Sources of minerals (food) rock salt such as sodium chloride (table salt).

The topic is presented step by step

Step 1: The class teacher revises the old topic

Step 2: The class teacher introduces the new topic

Step 3: The class teacher allows the pupils to give their own contributions and gives room for pupils” participation

Class Teacher and Pupils Activities. Interaction or Participation 

This involves class teacher and pupils’ interaction, conversation, imitation or modeling through discussion, play method or just by recitation or asking and answering questions that are related to the topic that has just been taught.

EVALUATION QUESTIONS

1. Define rock or what is a rock?

2.. Explain the following with examples:

• Plutonic rock
• Extrusive rock

3. Enumerate the primary and secondary minerals found in rocks.

4. List 3 types of rock and give 3 examples in each.

5. Enumerate the primary and secondary minerals found in rocks.
(a) List three major types of rocks.

(b) Describe the process by which the various types of rocks listed in (2a) above are formed.

6. Give 3 examples each of the following types of rocks:

(i) Igneous rock

(ii) Sedimentary rock

(iii) Metamorphic rock.

Conclusion : 

The class teacher concludes the lesson by giving the pupils some notes on the topic that has just been taught. He goes round to mark and he does the necessary corrections.