Resource Exploitation:Mining

Open cast mining. Image credit mutapamining.com

OPEN CAST AND STRIPPING (SURFACE METHODS)

• The open cast method is used when mineral deposits occur in horizontal seams which are near the surface not more than 50 meters deep.
• This method involves blasting which is carried out of scatter rocks.
• The overburden is then removed using large mechanical excavators or draglines.
• Open cast mining is used to extract coal at Hwange, asbestos in Mashava, nickel at Trojan mine in Bindura.

Advantages of opencast

• It is a fairly cheap and simple method of extracting shallow seams
• It is safer compared to the alternatives as there is no risk of tunnel collapse, explosions or gas poisoning
• The open pit allows easy access for humans and machines
• Requires less machinery and investment
• There is high selectivity which allows the operators to quickly get rid of low grade ores

Disadvantages

• Blasting causes structural damage to buildings as well as noise pollution.
• Use of explosive is a potential danger to miners.
• Opencast leaves the land scarred.
• Deforestation causes severe soil erosion. Mine dumps destroy the natural beauty of the land and landslides can occur on unstable dumps.

SHAFT METHOD

A miner descending into a shaft. Image youtube.com

• Shaft method is used to extract deep seated ores over 50 metres deep.
• The method involves the sinking of vertical or inclined shafts down to the level of the seams.
• Horizontal tunnels are built following the seams.
• Shaft mining is used to extract coal at Hwange, chrome in Shurugwi and gold in Mazowe.

Advantages

• The method allows extraction of deep seams.
• There is less deforestation.

Disadvantages

• It is very expensive.
• Cave-ins and toxic gases are a great risk.
• Deep mines can cause earth tremors.
• Flooding can be a danger to miners.

ADIT/DRIFT

Adit/Drift abandoned silver mine. Image credit ironminers.com

• This method is used to extract minerals that appear on the sides of mountains and valleys.
• This form of mining involves building horizontal or inclined tunnels along the mineral seam.
• Other structure such as conveyor belts and railway lines are built to facilitate the extraction of the minerals.

Advantages

• It is fairly cheap method and its safer than shaft mining method
• Can be drained using a force of gravity
• Minerals can be transported more easily and cheapily

Disadvantages

• Tunnels can cave-in.
• Landslides can occur.
• Can only be constructed where topology permits

To access more topics go to the O Level Geography Notes page