1
CH#1: Rocks & Minerals
1. (a) Structure of the Earth
The Earth’s internal structure is made up of three zones: the core, the mantle and the crust.
i) The core




The core is the innermost zone
It is made up mainly of iron and nickel.
Its thickness is almost 2900 km.
The temperatures in the core are about 3,000 0 C to 5000 0C.
ii) The mantle





It lies between the core and the crust.
It is made up of rocks.
It is mainly molten.
The temperatures in the mantle are about 800 0 C to 1600 0C.
Its thickness is almost 3000 km.
iii) The crust



It is the outermost zone.
It is made of a very thin layer of rocks.
It is only 5 km thick under the oceans and up to 100 km
(b) Types of Rocks
Rocks can be divided into three groups, according to how they were formed
i) Igneous rocks




These rocks are formed by fire.
They are associated with volcanic activity
Magma from the mantle ,which rises upwards the surface, forms igneous rocks
when it cools
Granite and basalt are the two most common types.
ii) Sedimentary rocks


Hamza Mir
These are made up of sediments
These sediments are small particals which are broken off from larger rocks.
03429450059
Rocks & Minerals & their Exploitation
2





After breaking, they eventually reach the seabed.
The weight of new sediments compress the layers below.
Sandstone (grains are concentrated in a rock)
Clay (Accumulation & Compression of Mud)
Limestone formed from the remains of plants and animals at sea bed
iii) Metamorphic rocks




These are rocks which have been changed by heat (contact metamorphism) and
pressure (regional metamorphism) in the Earth’s crust.
Rocks in contact with new magma flows are changed by the heat.
Rocks on plate boundaries are altered by the pressure and stress which accompanies
great Earth movement.
Limestone is changed into marble and clay is turned into slate.
(c) Distribution, types and reserves of major minerals



A mineral is a substance obtained by mining.
Minerals can be classified into metallic and nonmetallic minerals.
A reserve is a known source of the mineral, which has not yet been mined. The
minerals can be mined in the future when they are needed.
2. Methods of search and extraction of rocks and Minerals
(a) Opencast mining
The stages involved in this type of mining are:
 Clear the vegetation and remove the top soil.
 Break up and loosen the rock by using explosives
 Use diggers to remove the loose rock
 Tip the rock or mineral into trucks or railway wagons.
(b) Deep mining methods




Hamza Mir
Sinking a vertical shaft down to the rock layer containing minerals
Making a horizontal tunnel following the mineral layer
Extracting the minerals by digging done miners and machines
Bringing the loose rock from the mine and piling it up on waste heaps on the
surface.
03429450059
Rocks & Minerals & their Exploitation
3

Bringing the minerals to the surface, to be transported away in trucks or trains.
Factors that affect the decision to extract







Mineral resource must be Economically Viable (sufficient)
Profit for mining companies after covering all mining costs
Mineral is viable or not depends on supply and demand
Supply depends on known reserves (known to exist)
Demand depends on the need of the people (Varies)
World market price increases with increase in demand
Mines closed when demand decreases
Chances of mineral being exploited (mined and used)






Geological factors (either near the surface or deep underground)
Exploration & Feasibility (Sensitive local environmental issues)
Depletion rate(rate used up) – Large deposits with good quality or small reserves
with low quality and expensive to mine
Transport (close to industries with dense road network or remote places)
Climate (no extreme weather such as great heat, intense cold & heavy rain or
extreme weather conditions)
Price fluctuation (high demand low supply & high prices or low demand high supply
& low prices)
EXAMPLES


Cold polar regions in Alaska and Northern Canada & Siberia in Russia are remote
places are rich in minerals.
Cold winter hits Europe and North America increase the demand of Oil and Gas
which increase world prices.
IMPACTS OF MINING ON ENVIRONMENT







Hamza Mir
Surface waste heaps (worst after heavy rain & mine waste can be highly toxic)
Leaks form Oil wells and pipelines
Remote areas need road and railway network causing deforestation
Weak government control while mining companies are dominating (Drilling rights for
oil and gas in Kirthar National Park in Pakistan)
Air pollution due to dust and fumes from chimneys during crushing mineral ores
Tall chimneys destroy scenic beauty
Water pollution
03429450059
Rocks & Minerals & their Exploitation
4

Open cast mining leave big scars on land
IMPACTS OF MINING ON PEOPLE
Positive Impact





Foreign exchange income through export of minerals
Income can be used to import from other countries (African countries)
Improve the quality of life by improving infrastructure
Job opportunities (Miners are better paid than farmers)
Mining can be done where few other ways of making a living (driest places)
Problems related to deep mining





Deep mining is dangerous
The roof of the tunnel can be collapsed and miners are trapped injured or killed
Flooding
Dangerous gases in mines, which increase the danger of fire and explosion
Ventilation
Uses of rocks and minerals










Chalk is used for cement
Gravel is used for concrete
Clay is used for bricks and pottery
Sand is used for glass
Limestone is the material for making cement and concrete.
Copper is used for making electric wire
Lead is used making cables and batteries
Bauxite is used for making aluminums and transport and domestic equipment
Sulphur, salt and potash are used in the chemical industry
Gold ,silver and diamond are used in making jewelry
(h) Conservation of environments damaged by mining




Landscaping/restoration: reclamation should be done by filling the dugged hole, and
vegetation cover grown on that place, so that the land can be used again.
Landfilling: old quarries and large holes left after the mining stopped are often
convenient places for the disposal of waste. It is a cheap and easy way to dispose of
waste.
Installing water filtration plants at the sites of mining.
Reforestation of the deforested areas.
Hamza Mir
03429450059
Rocks & Minerals & their Exploitation
5

Installing precipitators and catalytic converters at the site of mining. A precipitator is a
device for removing dust particles from a gas. Similarly a catalytic converter is a device
that controls the emission of toxic gases and converted them to less toxic variants.
Hamza Mir
03429450059
Rocks & Minerals & their Exploitation