Renewable and non-renewable resource formation: WACE Year 12 Earth and Environmental Science
“Explain how Earth processes form renewable and non-renewable mineral and energy resources”
Resources form when transfers and transformations of matter and energy concentrate useful materials in the geosphere. Non-renewable resources such as ore minerals and fossil fuels form over geological timescales and are effectively finite, while renewable resources such as solar, wind, hydro and biomass are replenished on human timescales by ongoing energy flows.
What this dot point is asking
SCSA wants you to classify resources and explain the Earth processes that form them. A strong answer links each resource to the spheres involved and to the rate of formation, because rate is what separates renewable from non-renewable.
Classifying resources by rate of replenishment
A non-renewable resource forms so slowly, over millions of years, that it cannot be replaced within a human lifetime. Once extracted it is depleted. A renewable resource is replenished by continuing natural processes on a timescale of days to decades, so it can be used indefinitely if extraction does not exceed the replenishment rate.
The key idea SCSA emphasises is that resources are concentrations of matter and energy produced by interactions of Earth systems. A useful deposit exists only where a process has concentrated a material far above its average crustal abundance.
Ore: rock containing a mineral in high enough concentration to be mined profitably. Concentration factor: how much a deposit is enriched above average crustal abundance. Reserve: the portion of a resource that is economically and technically recoverable now.
Formation of mineral resources
Metallic mineral deposits form where geological processes concentrate metals.
- Magmatic processes: as magma cools and crystallises, dense minerals settle and concentrate. Nickel, chromium and platinum deposits form this way.
- Hydrothermal processes: hot, mineral-rich water moves through fractures and deposits metals as it cools. Many gold and copper deposits, including those of the Kalgoorlie goldfields in Western Australia, are hydrothermal.
- Sedimentary and weathering processes: chemical weathering can leave behind enriched residues. The vast banded iron formations of the Pilbara formed when oxygen from early photosynthesis reacted with dissolved iron in ancient oceans, precipitating iron oxides over hundreds of millions of years.
Bauxite (aluminium ore) in the Darling Range near Perth formed by intense tropical weathering that leached away soluble elements and left aluminium-rich residue. This shows the biosphere, atmosphere and hydrosphere all shaping a geosphere resource.
Pilbara banded iron formations record the Great Oxidation Event. Photosynthetic cyanobacteria released oxygen that combined with dissolved iron to precipitate iron oxide layers, linking the biosphere directly to one of Australia's most valuable ore resources.
Formation of fossil fuel resources
Fossil fuels are non-renewable energy resources formed from the buried remains of organisms.
- Coal forms from plant matter that accumulated in swamps, was buried, and was compressed and heated over millions of years, progressing from peat to lignite to bituminous coal.
- Oil and natural gas form from marine microorganisms whose remains were buried in fine sediment. Heat and pressure transformed the organic matter into hydrocarbons, which then migrated and collected in porous reservoir rocks beneath impermeable cap rocks. The North West Shelf gas fields off Western Australia are a major example.
Fossil fuels store ancient solar energy captured by photosynthesis, so their formation also links biosphere and geosphere.
Formation of renewable energy resources
Renewable resources are driven by continuous external and internal energy flows.
- Solar energy arrives constantly from the Sun.
- Wind results from uneven solar heating of the atmosphere.
- Hydro depends on the water cycle, itself solar-powered, lifting water that then flows downhill.
- Biomass stores recent solar energy in living material.
- Geothermal taps heat from Earth's interior.
Because these flows are continuous, the resources are renewable, but they are not unlimited at any moment: output depends on conditions such as sunlight, wind speed and rainfall.
State the test
A resource is renewable only if its rate of natural replenishment is comparable to or faster than the rate of human use. Apply this test, do not just memorise a list.
Worked case: groundwater
Groundwater in a confined aquifer may recharge over thousands of years. If a town pumps it faster than recharge, the water table falls and the resource is effectively mined, behaving as non-renewable despite water being a renewable substance in principle.
Worked case: native hardwood timber
A jarrah forest regrows, but slowly (decades to a century for mature trees). Harvest at or below the regrowth rate is renewable; clear-felling faster than regrowth depletes it.
Conclusion
The label depends on the use rate versus replenishment rate, not the material alone. This is exactly the distinction SCSA wants you to apply to unfamiliar examples.
- Calling all renewables unlimited
- Renewable means continuously replenished, not infinite at any instant. Overuse of groundwater or biomass faster than it recharges depletes it.
- Saying coal forms quickly
- Fossil fuels take millions of years to form, which is why they are classified as non-renewable.
- Ignoring sphere interactions
- SCSA wants you to name which spheres interact, for example the biosphere supplying organic matter for coal and oil.
- Confusing a resource with a reserve
- A reserve is only the part that is economically recoverable now; the total resource is larger.
Exam-style questions
Questions in the style of SCSA exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.
WACE 2021-style6 marksA mineral deposit contains copper at an average grade of 0.6 percent, while the average crustal abundance of copper is about 0.006 percent. Calculate the concentration factor of the deposit and explain the geological process most likely responsible for concentrating the copper to this level.Show worked answer →
A 6 mark answer rewards the calculation plus a correctly reasoned formation process.
Calculation. Concentration factor . The copper is concentrated about 100 times above average crustal abundance.
Process. Such enrichment of copper is typically achieved by hydrothermal processes. Hot, mineral-rich fluids circulate through fractures in the crust, often driven by nearby magma; as the fluids cool or react with surrounding rock, dissolved copper precipitates as sulfide minerals in veins or disseminated zones, concentrating it far above background levels.
Markers reward the correct concentration factor with working, and a valid concentrating mechanism (hydrothermal) with a brief explanation of how it enriches the metal.
WACE 2022-style8 marksCompare the formation of a non-renewable resource (coal) with a renewable resource (hydroelectric energy), and discuss what the comparison reveals about sustainable resource use.Show worked answer →
An 8 mark answer needs a structured comparison plus a sustainability judgement.
- Coal formation
- Plant matter accumulates in swamps, is buried, then compressed and heated over millions of years (peat to lignite to bituminous coal). The rate of formation is geologically slow, so once burned the resource is effectively gone, making it non-renewable.
- Hydro formation
- Hydroelectric energy depends on the water cycle: solar energy evaporates water, which precipitates at altitude and flows downhill, and this gravitational potential energy is converted to electricity. The driving energy flow is continuous, so the resource is replenished on human timescales.
- Comparison and judgement
- Both ultimately trace to solar energy, but coal stores ancient solar energy released far faster than it forms, while hydro uses present-day energy flows. Sustainable use means matching extraction to the rate of replenishment: coal cannot be used sustainably because it does not replenish, whereas hydro can be sustainable provided river flows and ecosystems are not over-exploited. The key insight is that rate of replenishment, not the resource itself, determines sustainability.
Markers reward a parallel comparison of formation rate and energy source, and an explicit point that sustainability depends on replenishment rate.