Mining - Geography Form 1
The valuable minerals extracted during mining may either be in solid, liquid or gaseous form. There are different minerals found in different parts of East Africa. Some of the minerals found in E. Africa are Trona in lake magadi in Kenya , copper in Kilembe Uganda and diamonds in Mwadui Tanzania.
Some of the minerals occur in small quantities while others are found in large quantities. Some are found in remote areas making their exploitation difficult and expensive.
By the end of the session, the learner should be able to,
- define the term mining.
- to describe methods of mining.
explain the effects of mining to the environment
Panning is the simplest technique of extracting minerals from alluvial deposits. Panning involves out alluvial deposits from the river bed and whirling it with water in a shallow pan. The pan is tilted to drain away the lighter material leaving behind the heavier mineral.
Panning is done on a very small scale by individual prospectors for example, in Kenya, small amounts of gold are mined through panning of materials from the bed of River Morun in west Pokot. In South Africa individuals use panning to mine diamonds found near the river beds.
The other alluvial or placer technique of mining is dredging.This involves digging out minerals mixed with alluvial deposits and submerged in river beds or lakes. The dredger scoops the mixture which is passed through sloping channels to separate the heavier minerals from the lighter and unwanted materials.
A dredger is a machine which floats on a river or lake.Dredging is an expensive method of mining so it is used only where there are large mineral deposits.
The other alluvial mining technique is hydraulic mining method. This is a common method used where alluvial deposits occur on valley sides or form thick terrace like deposits. It involves the use of powerful of water directed at the exposed are on a slope. This is to flush out thick minerals deposits.
Effect of mining to the environment
By the end of the session, you should be able to explain the effects of mining to the environment.
Effects of mining
You have been learning about
Effects of mining on the environment during exploration, extraction and closure of mines
Review what you have learnt by creating an illustration to summarize the effects of mining.
Animate the sequence:
Click nos 1-5 in a sequence to create the illustration
Refer to the original handwritten document for the diagram.
Use different colours for the boxes
One of the effects of mining on the environment is the destruction of natural vegetation. Before the minerals are extracted, the land is cleared for mining site, construction of roads and buildings.
Closely related to the clearing of vegetation is soil erosion. After the clearing of the land, the soil is exposed to agents of erosion such as wind and water.
During mining a large amount of solid wastes such as rocks and debris are scattered around the site. The heaps of rock wastes make the land ugly.
Mining usually requires the use of heavy machinery. The use of the heavy machinery causes intense noise. This is referred to as noise pollution. Miners often suffer deafness when continuously exposed to intense noise.
Other negative effects of mining are water pollution and air pollution. Wastes from the mines may flow into the rivers and lakes thus polluting the water.
Poisonous gases and dust released in the atmosphere may cause respiratory diseases suffocation and poor visibility.
After mine closure
When minerals are exhausted, the mines close down leaving behind large open pits. These pits are ugly.They may also be filled with water providing breeding grounds for mosquitoes which cause malaria. People and animals may drown in such water.
Trona in lake Magadi
By the end of the session, you should be able to describe the occurrence and exploitation of Trona on Lake Magadi
A Study of Trona on lake Magadi in Kenya
In the Rift valley province of Kenya, there are many lakes. Some of the lakes contain fresh water while others contain salt water.The only lake that contains Trona is Magadi. Lake Magadi lies on the floor of the Rift valley about 120 KM to the South West of Nairobi. It is also the biggest single source of mineral wealth in Kenya.
Voice over: Click in the correct box to describe the appearance of some igneous rocks.
The surface of the rocks with vesicular texture is rough ? smooth
Formation of Trona
In our lesson today, we have Mr. John Odupoy to help us understand how trona is formed in lake Magadi.
Mining on Lake Magadi has been going on since 1914. The lake contains thick layers of trona deposits that reach a depth of 30 Metres.These layers of trona consists of different salts. The main salts are:
- Sodium chloride and
- Sodium sesquicarbonate
The high temperatures inside the earth heats the water underground. The hot water dissolves the soda salts in the rocks beneath the lake. The solution of soda salts is hot and light. As a result, it rises to the surface of the lake Due to the high atmospheric temperature, the water evaporates, leaving solid crystals of trona on the lake
Extraction and processing of Trona
Trona is mined using the placer mining method. It is mined using the dredging technique. In this technique a special machine called a dredger is used.
Play the video clip to view the Extraction and processing procedure
Dredger scoops the trona from the surface of the lake
he scooped trona is fed into a crusher inside the dredger and mixed with lake water (lake liquor).
The mixture is pumped through a pipeline to the factory
At the factory the trona crystal are washed with clean water to remove the liquor. The liquor is pumped back to the lake.
The cleaned crystals are carried on a conveyer belt to huge boilers, where they are heated and dried to form soda ash
The dried soda ash is crushed into smaller sizes and packed in bags ready for the market.
Uses of soda ash
Soda ash is used in the manufacturing of glasses and bottles, soaps and detergents, paper making, dyes for textiles and for softening water.
Uses of soda ashSoda ash is used in various ways. The photograph below shows the various uses of soda ash.
Benefits of trona mining to the economy of Kenya
The mining of trona has led to urbanization by contributing to the development of Magadi Town
It has stimulated the development of road and rail transport
It has provided employment to many Kenyans thus raising the living standards
The local people benefit from free water for their use.
Through exports of soda ash the country earns foreign currency
It has contributed to the development of social amenities such as hospitals and schools that have benefited the local people.
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