Extraction of Rocks and Minerals from the Earth (IGCSE Environmental Management)

Extraction of Rocks and Minerals from the Earth

v Minerals provide us with a wide range of materials that we use in everyday life.

v Coal and oil provide energy and many chemicals used in industry.

v Metallic ores provide us with the metals and alloys needed to make products such as computers, mobile phones, cars, wires, and nails.

v The demand for minerals continues to increase, both from developed and developing countries.

v  People have searched for minerals for thousands of years. The simplest way to find mineral deposits is to look carefully at the surface of rocks. This process of prospecting has found nearly all the surface deposits of minerals worldwide.

Exploring for Minerals:

·        Prospecting: a process of searching for minerals by examining the surface of the rocks.

•   Remote sensing: a process in which information is gathered about the Earth’s surface from above.
•    Photographs of the area are taken from the air.
• The images are carefully analyzed for mineraAerial photography can cover more ground than a person on the surface

• Radiation detection:

▪        Mineral deposits are weathered at the Earth’s surface, forming mineral oxides.

▪       They can be detected by their unique radiation pattern (recorded by a satellite and downloaded to a computer for analysis).

·        Satellite signals:

▪     Some satellites send signals to the Earth’s surface and collect the reflected signals, indicating the presence of minerals.

▪    The system works in all weather conditions.

·        Satellite images:

• Computers are used to process the data from a region of interest to check for mineral presence.
•  Geologists confirm the presence of the mineral by visiting the location.
•  Geologists can further check the availability of the mineral in nearby areas.
• Using satellites saves time and costs less.

 Geochemical analysis:

•    analyzing the chemical properties of rocks(by taking samples).
• The samples can be taken from stream sediments, soil or rocks (using shallow drilling).
• The location of the sample points can be accurately found using the Global Positioning System (GPS).

·        Geophysics: method to identify mineral ores present in rocks using their physical properties.

▪     A series of vibrations are sent through the Earth’s surface.

▪   Several sensors are placed at different distances from the source of vibrations on the surface.

▪    The vibrations create shock waves that travel down into the rock layers.

▪   They are reflected back to the sensors on the surface.▪    The shock waves record different patterns depending on the minerals present in the rock layers.

Methods of extraction:

 ·        Surface Mining: includes open-cast (open-pit, open-cut) and strip mining.

 v Open-pit mining is used when a valuable deposit is located near the surface.

The material above the deposit is called overburden.

v The vegetation is cleared and topsoil removed.

v The rocks are broken up and loosened with explosives.

v The loose rock is removed using diggers.

v The rock or mineral is tipped into trucks or railway wagons.

v Building materials such as sand, gravel and stone are removed from open pits called quarries.

v The overburden (overlying rock and soil) is removed as a thin strip.

v It is mainly used to mine coal.

·          Sub-surface mining: includes deep and shaft mining.

▪    A vertical shaft is sunk down to the rock layer containing minerals.

▪      A horizontal tunnel (adit, drift) is made, following the mineral layer.

 v  The minerals are extracted by digging (by machines and miners).

v  The loose rock is brought from the mine and piled up on waste heaps on the surface.

v The minerals are brought to the surface and transported in trucks or trains.

  Compared with open-pit mining, any form of shaft mining is more difficult because a supply of fresh air and water drainage has to be provided. There are also the dangers of collapsing tunnels as well as the risks of poisonous gas, explosion, and underground fire.

 

Factors that affect the decision to extract rocks and minerals:

·         The costs of exploration and extraction:

▪  Probable cost of extracting one tonne is calculated.

▪    There are fewer technical difficulties of mining on a large scale using open-pit mining as there’d be low extraction costs per tonne.

▪    Shaft mining is costlier to set up and maintain as the cost per tonne will be higher. So, only deposits of higher value can be mined in this way.

·        Geology:

▪       High-grade ores yield more of the required chemical elements than low-grade ores.

▪   Small deposits of high-grade ore are worth mining.

▪    Small deposits of low-grade ore that cannot be mined at a profit are left as reserves.

·        Accessibility:

▪  Transporting the ore from the mine to processing plants can be difficult and expensive.

▪     The cost of building road or rail links to the processing plant or to the nearest port for export has to be considered.

▪        Carrying out some processing at the mine reduces transport costs.

▪       The mining company must be given a license before extracting a deposit.

▪       A long-term agreement between the government and mining companies must be reached to avoid rapid rises in the tax, which makes mining unprofitable.

·            Environmental Impact assessment:

▪  For a license application to be approved, the company must have a plan to keep the loss of habitat minimal, followed by the restoration of land proceeding the completion of mining.

▪   The choice of site for mine waste should also be considered.

Supply and demand: the relationship between how much of a commodity is available and how much is needed or wanted by the consumers.

▪    Increase in world demand for any mineral ore will elevate the prices.

▪     The profit from a working mine depends on changes in supply and demand.

▪    If the demand is too high, mines that were not profitable before become worth mining.

▪   If the demand falls, working mines may get into a loss due to the transport and extraction expenses.

Key Terms:

ore: a rock with enough of an important element to make it worth mining

Prospecting: a process of searching for minerals

Remote sensing: a process in which information is gathered bout the Earth’s surface from above

Geochemical: the chemical properties of rocks

Geophysical: the physical properties of rocks

Surface mining: a type of mining used when the mineral is either exposed on the surface or overlain by only small amounts of overburden

overburden: the rock and soil overlying an economically viable mineral deposit

open-pit mining: a type of surface mining

Strip mining: a type of surface mining

Sub-surface mining: a type of mining used when the deposit is covered by a deep layer(s) of unwanted rock

Deep mining: a type of sub-surface mining

Shaft mining: a type of sub-surface mining

Impact of rock and mineral extraction

https://greenliving.lovetoknow.com/How_Does_Mining_Affect_the_Environment

 1.   Environmental impacts

Impacts on the environment from the extraction of rocks and minerals range from large-scale habitat destruction to pollution of the atmosphere, land and water. Those living near the site are also affected by noise and visual pollution.

a.   Ecological impacts

·        Loss of habitat for some species of plants and animals. As the vegetation is cleared, the plants removed have lost a place to grow, so the animals that depend on the plants for food and shelter are affected.

·        At the beginning of deep mining operations (as shafts have to be dug down), only a small area of land is cleared. After this type of mine has been working for several years, more habitats will be destroyed as the amount of mine waste stored aboveground increases.

·        After the seams of the valuable minerals have been removed, the overburden is spread over the mined area to restore the land. The new land surface will slowly become covered in some plant species. However, this vegetation will have less biodiversity compared with the original vegetation. This means that some plant and animal habitats will still be lost from an area for many years, even though the land surface has been restored.

·        When a company applies for a license to start working, an environmental impact assessment is carried out. The licence application is usually approved if the company has a plan to keep the loss of habitat as small as possible and then to restore the land after mining has finished.

 

·          Environmental impact assessment: a process by which the probable effects on the environment of development are assessed and measured.

 b.   Pollution

·        The working life of any type of mine will result in some pollution of the environment

▪   Noise pollution: due to machinery and explosive disturbs the behaviour of animals species and causes hearing problems for people. Deep mining produces less noise than surface mining.

·        Water pollution: water supplies may also be polluted, making it unsafe for people to drink.

·        The water may become acidic and dissolve toxic metal ions-this combination kills many aquatic organisms.

·        Some of the metal ions exist only in low concentrations in bodies of water. However, organisms absorb these ions and retain them in their body, reaching concentrations much higher than that in the water. This is called bioaccumulation.

·        The concentrations increase further in organisms that are higher up the food chain and can cause the death of top consumers. This process is called biomagnification

 

·        Land pollution: toxic nature of the waste doesn’t allow plant growth even years after the mining is stopped.

·        Air pollution: mining activities release dust particles, which will settle on the vegetation near the mine. Dust reduces plant growth: the leaves of plants need to absorb light energy to perform photosynthesis. If light cannot penetrate a layer of dust on a leaf surface, then the rate of photosynthesis is reduced.

·        Dust from mining activities may also have toxic effects. This can also reduce or stop plant growth, and the particles can be dangerous to human health.

·        Breathing in dust that then remains in the lungs can lead to serious lung diseases that can cause death.

·        Some harmful substances can also be absorbed through human skin.

·        Visual pollution: Evidence of mining activity can often be seen because the landscape is damaged.

1.   Economic impacts:

·        Provides employment for people and provides taxes for the government.

·        Number of people will be directly employed to extract minerals. Further jobs are created if the mineral is then refined and processed in the same country.

·        If all these activities occur in the same country, this will generate the most income for buying goods and services as well as investing in infrastructure projects.

·        Improvements to transport and services, such as healthcare and education, will be required to supply any mining industry as well as support the mineworkers and their families.

 Managing the impact of rock and mineral extraction Safe disposal of mining waste:

· waste will be stored to prevent collapse.

·        The site of the mine waste must also prevent the possibility of water pollution.

·        The waste must be monitored to detect any movement or further pollution.

Land restoration and bioremediation:

·        Soil improvement:

·        When mining has finished, the land needs to be restored.

·        The waste can then be covered by a layer of soil, which may be enriched with fertiliser.

·        Planting Trees:

• ·        After improving the soil fertility, plants and trees can be grown in that area, helping an ecosystem to be reborn.
• ·        Bioremediation: a process of removing pollutants from waste using living organisms.
• ·        In situ treatment: treatment of contaminated waste where it’s left.
• ·        Ex situ treatment: removal of contaminated waste from a site to a treatment plant. Often happens slowly (can be sped up by providing oxygen and nitrogen).
• ·        Microorganisms, like bacteria, can absorb pollutants and metabolise them into less harmful substances.
• ·            Some plants have the ability to bioaccumulate toxic metals.·        After these plants grows for a while, the parts of the plants aboveground are removed so the waste in the ground becomes less toxic.
• ·            Making lakes and natural reserves:

·        Several tree and herb species are introduced.

·        As their populations grow, they create habitats for many species.

• ·        These nature reserves become valuable green spaces for human recreation and help in maintaining biodiversity.
• ·        If the rock lining the hole (created by the extraction) is non-toxic and impervious to water, it can be filled with water to form a reservoir or lake.
• ·        It is used for irrigating farmland or processing to provide clean, safe drinking water for humans.
• ·            Using as landfill sites:
• ·        Landfilling: the waste is tipped into a hole; from time to time it is levelled off and compacted.
• ·        Sanitary landfilling: As in landfills, the waste is used to fill the hole, but alternating layers of waste and sand are used.
• 
  
• Key Terms:

Environmental impact assessment: a process by which

the probable effects on the environment of development are assessed and measured.

Biomagnification: the process in which the concentration of

a substance in living things becomes higher at progressively

higher levels in a food chain or web. 

Bioremediation: a process in which living things are used to remove toxic chemicals from a natural site

Sustainable use of rocks and minerals

·        Sustainable use means use that meets the needs of the present without affecting the ability of future generations to meet their needs.

·        Sustainable resources will never run out, and this can be achieved in fisheries, agriculture and forestry, where the resource is biological and can be regrown. Unlike these biological systems, such things as rocks and minerals will not last indefinitely.

·        The sustainable development of the reserves of any rock or mineral must take into account environmental, economic and social factors.

Sustainable resource: a resource that can be continuously replenished e.g. agriculture, forestry, etc. 

Sustainable development: development that meets the needs of the present, without compromising the ability of future generations to meet their own needs.

Strategies for the sustainable use of rocks and minerals:

·        Increasing the efficiency of the extraction of rocks and minerals:

▪    Mine wastes must be processed for the second time.

▪    This allows the valuable minerals to be recovered and reduces the risk of pollution due to mine waste.

▪     Chemical treatment of the waste and biological treatment (using microorganisms) extracts much of the valuable mineral still within it.

▪    Improvements in the performance of the machines used in mining and processing.

▪     Greater use of data analysis by computers (to predict geological conditions).

 

·        Increasing the efficiency of the use of rocks and minerals:

▪    Engineering solutions e.g. design steel beams with the same strength but using less steel.

·        The need to recycle rocks and minerals:

▪    Recycling uses less energy than processing the ores.

▪     Recycling also produces less waste and thus, reduces the risk of pollution.

·        Legislation:

▪    The governments pass laws that require manufacturers to become responsible for recycling and reuse.