A-Level Environmental Science: The Physical Environment - Lithosphere and Mineral Extraction

Comprehensive practice questions covering formation processes, exploration methods, extraction viability, environmental impacts, and future mineral supply techniques from Lesson 14-18.

What is the composition and thickness of the lithosphere according to the notes?

The lithosphere consists of the crust ($0$-$70\,\text{km}$) and the uppermost solid mantle ($70$-$2891\,\text{km}$).

Why are materials extracted from the lithosphere described as non-renewable and depletable?

They form at such a slow rate that the amount humans use cannot be replaced, meaning the supply will one day run out.

What are three strategies humans can use to continue extracting minerals from the lithosphere sustainably?

1. Find alternatives to reduce demand. 2. Increase supplies by harvesting from new locations. 3. Extend useful lifetime by recycling materials.

How is a mineral ore defined?

A rock or solid material from which a mineral can be extracted for a profit.

What are examples of minerals used for industrial processes and construction?

Industrial minerals include halite (salt) and gypsum (plaster); construction minerals include limestone and granite.

What is the process of hydrothermal deposition?

Superheated water under the Earth's crust dissolves minerals in surrounding rocks; as the water moves away from the heat and through fissures, it cools and causes minerals to precipitate out.

Define metamorphism and give two examples of rock transitions.

Metamorphism occurs when sedimentary and molten rock come into contact, causing recrystallization due to high pressure and temperature. Examples: limestone becomes marble, and mudstone becomes slate.

How were Proterozoic marine sediments, specifically banded iron formations, formed?

Oxygen combined with iron in the water to form insoluble iron oxide, which sank to the ocean floor and formed layers over time.

What are placer deposits and where are they likely to form?

Deposits where minerals are concentrated when high-velocity water suddenly slows down and loses kinetic energy; they often form on the inside of river meander loops or below waterfalls.

What three characteristics must minerals have to form placer deposits?

They must be unreactive, have high density, and be difficult to break up into fragments.

How do evaporites like halite form?

They form when a section of the ocean evaporates, leaving behind salt deposits.

Give three examples of biological sediments.

1. Limestone formed from exoskeletons and shells. 2. Coal formed from terrestrial plants. 3. Oil and gas formed from marine microbes.

How does magnetometry work in mineral exploration?

A magnetometer measures the Earth's magnetic field to look for variations caused by magnetic ore bodies, such as haematite.

What is a limitation of magnetometry and gravimetry?

They can signal the location of an anomaly or variation but cannot identify the specific ore type or the depth of the deposit.

What causes a positive anomaly in a gravimetry survey?

Objects with a large mass or density, which produce a bigger gravitational force.

How does infrared spectroscopy facilitate satellite surveys for minerals?

It measures the wavelength of IR radiation emitted from the ground to identify mineral locations.

Explain the mechanism and use of seismic surveys.

Loud sounds or vibrations are created in the crust, and geophones measure the reflection time at geological boundaries to understand the size and depth of oil and gas deposits.

In resistivity surveys, what indicates a lower resistivity in rocks?

Rocks that contain water, such as sedimentary rocks, or rocks containing metals.

Why is trial drilling considered the most critical exploration technique before mining?

It is the only technique that takes physical samples to determine depth, purity, and chemical form, allowing for the assessment of economic viability.

Define the terms 'grade' and 'cut-off grade' (COOG).

Grade is the percentage of the rock that is metal (purity); Cut-off grade is the minimum percentage of metal required for a deposit to be economically viable to extract.

Differentiate between stock, resource, and reserve.

Stock is all material in the lithosphere; Resource is material that could theoretically be exploited in the future; Reserve is the portion that can be extracted economically right now.

What is Lasky's Principle?

As the purity of a mineral decreases, the quantity of the mineral on Earth increases exponentially.

Compare habitat destruction in deep mining vs. surface mining.

Deep mining has fairly low surface habitat destruction, whereas surface (open cast) mining causes a much higher degree of habitat destruction due to large, shallow pits.

When is dredging used for mineral extraction?

When a mineral deposit is submerged in water on land, by the coast, or in shallow marine environments.

What is 'overburden' and how is it typically removed?

The rock situated above a mineral deposit; it is usually removed via controlled explosions.

How can the hydrology of a mine site affect its economic viability?

If the rock is impermeable, expensive drainage systems must be installed to prevent flooding.

What is directional drilling and why is it environmentally beneficial?

Drilling that occurs horizontally; it allows the drill site to be outside protected areas while still reaching deposits underneath them.

How can water sprays mitigate dust pollution at mine sites?

Water coats the dust, making it denser so it falls to the ground instead of remaining mobile in the atmosphere.

Explain how baffle mounds reduce environmental impact.

They are embankments, fences, or trees installed to absorb and deflect noise pollution from vehicles and explosives.

What is habitat fragmentation in the context of mining infrastructure?

The building of roads or railways that separates populations, preventing them from interbreeding and decreasing the gene pool.

What are two methods to make spoil heaps more stable and aesthetically pleasing?

1. Planting trees/plants so root networks bind the structure. 2. Reducing the angle of the slope by flattening the top.

What is toxic leachate (acid mine drainage) and how is it managed?

Acidic water formed as precipitation dissolves metals in spoil heaps; it is managed by neutralising it with an alkali like calcium carbonate to precipitate metals.

How do collection lagoons prevent turbidity in nearby water bodies?

Water is kept still so sedimentation can occur, allowing suspended solids to sink to the bottom before the water is released.

What is subsidence in mining?

Small slippages where the ground at the surface above a mine slips, causing cracks in foundations and buildings.

Describe the process of bioleaching.

Bacterial or fungal species use enzymes to oxidise sulphide ores, releasing sulphuric acid which dissolves metals for collection via electrolysis.

Explain phytomining.

Plants are grown on spoil heaps to absorb metal ions into their leaves; the plants are harvested and incinerated, and the resulting ash is treated with acid to extract metals via electrolysis.

What is polymer adsorption used for in mineral extraction?

Extracting metal ions (like Uranium) from trace concentrations in seawater by using long-chain molecules to which the ions attach.

What are manganese nodules and where are they found?

Mineral-rich lumps containing manganese, copper, and nickel found under the seabed in benthic habitats.

What is 'cradle to cradle' design?

Designing a product so that at the end of its life, it is easy to separate and identify components for reuse or recycling.

List two advantages and two disadvantages of recycling minerals.

Advantages: Conserves resources and reduces energy use/environmental impacts of mining. Disadvantages: Mixed materials can be difficult to separate and the process may rely on inconsistent consumer cooperation.