ROCKS AND MINERALS Flashcards
What is Igneous Rocks
Igneous rocks:
Made when liquid magma cools to form solid rock.
Molten rock below the surface is called magma, and lava when it reaches the surface.
Extrusive igneous rock: if the rock cools quickly, small crystals, e.g., basalt, are formed.
Intrusive igneous rock: if the rock cools slowly, large crystals, e.g., granite, are formed.
Examples: Granite and Basalt
Define Sedimentary Rocks
Sedimentary rocks:
Formed by the weathering of existing rocks at the Earth’s surface.
Fossils may be present.
Sediments (small particles of rocks) accumulate into layers and get pressurized due to the newer deposits above them.
The sediments are transported by water and wind (erosion).
Particles like clays, silts, sands, gravels, and small boulders are found in sediments.
Define Metamporphic Rocks
Metamorphic rocks:
Formed from the existing rock when heat and/or pressure causes changes in the rock crystals without melting it.
The changes can be physical, chemical, or both.
Examples: marble and slate.
Define Prospecting
Prospecting: a process of searching for minerals by examining the surface of the rocks
Define Ore
Ore: A rock with enough important mineral to make it worth mining
Define Remote Sensing method for rocks exploration
Remote sensing: a process in which information is gathered about the Earth’s surface from above.
Photographs of the area are taken from air.
The images are carefully analysed for mineral presence.
Aerial photography can cover more ground than a person on the surface.
How are Satelites used for exploration of Rocks
Satellite signals:
Some satellites send signals to the Earth’s surface and collect the reflected signals, indicating the presence of minerals.
The unique radiation pattern is processed and analyzed by computers
The system works in all weather conditions.
The GPS gives the exact location.
Large area covered in low-cost
Most efficient method
How is geochemical analysis and field is used in rocks exploration
Geochemical analysis and field surveys
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).
How is Geophyics used for rocks exploration
Geophysics: method to identify mineral ores in rocks using their physical properties.
A series of vibrations (seismic waves) 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 to the sensors on the surface.
The shock waves record different patterns depending on the minerals present in the rock layers.
Explain Sub Surface mining
Surface mining includes open-cast (open-pit, open-cut) and strip mining.
Open-pit mining is used when a valuable deposit is located near the surface.
The vegetation is cleared, and topsoil is removed
The rocks are broken up and loosened with explosives.
The loose rock is removed using diggers.
The rock or mineral is tipped into trucks or railway wagons.
Building materials such as sand, gravel, and stone are removed from open pits called quarries.
Strip mining is used to mine a seam of mineral.
The overburden (the unwanted overlying rock and soil) is removed as a thin strip.
It is mainly used to mine coal and lignite
Explain Sub Surface Mining
A vertical shaft is sunk into the rock layer containing minerals.
A horizontal tunnel is made, following the mineral layer.
The minerals are extracted by digging (by machines and miners).
The loose rock is brought from the mine and piled up on waste heaps on the surface.
The minerals are brought to the surface and transported in trucks or trains
Resources: Gold and Diamonds
What are the factors the decision making to extract minerals (mention 2)
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 the nearest export port must be considered.
Carrying out some processing at the mine reduces transport costs.
The mining company must be given a licence 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.
What are the factors which affect the decision to extract minerals (mention 2)
Environmental impact assessment:
For the license application to be approved, the company must have a plan to keep the loss of habitat minimal, followed by the restoration of land and the completion of mining.
The choice of site for mine waste should also be considered.
Supply and demand: the relation between how much of a commodity is available and how much is needed or wanted by the consumers.
An 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 becoming worth mining.
If the demand falls, working mines may lose due to the transport and extraction expenses.
What are the impacts of Rock and Minerals Extraction
Ecological impacts:
Loss of habitat as the vegetation is cleared
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∴ plants do not have a place to grow, so the animals depending on them for food and shelter are affected.
Pollution:
Noise pollution: due to machinery and explosives
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∴ disturbs the behaviour of animal species and causes hearing problems for people.
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.
Bioaccumulation: organisms absorb and retain the ions in their body, reaching a concentration higher than that in water.
Biomagnification: the concentrations increase higher up in the food chain and cause the death of top consumers.
Land pollution: The toxic nature of the waste doesn’t allow plant growth even years after the mining is stopped.
Air pollution: dust particles settle on the vegetation, not allowing sunlight to reach the leaves and thus reducing the rate of photosynthesis.
Breathing in dust that remains in the lungs can cause serious lung diseases.
Visual pollution: the landscape is damaged.
What are the economic impacts of Mineral Extraction
Jobs are created in the extraction and transporting of minerals
Increase in the Country’s economy
Earn foreign exchange.
The income earned can be used for buying goods and services and investing in infrastructure projects.
Improvements to transport
