Rocks, the rock cycle and permeability
Explain how the syllabus rocks form, how material moves through the rock cycle and why different rocks allow water through at different rates.
Section 1 · Natural resources
This original StudyForA sequence supports Cambridge IGCSE Environmental Management 0680 Topics 1–4 for exams in 2027, 2028 and 2029. Named local examples are chosen by the learner and centre; verify current conditions and local context with reliable sources. It is not a Cambridge paper, official grade or complete course.
Before you begin
- Use the 2027–2029 syllabus and check your exam year and centre's entry arrangements. Topics 1–4 are taught on this page; Topics 5–7 are still being built.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which rock in the syllabus is classified as permeable?
What you will learn
- Explain how the syllabus rocks form, how material moves through the rock cycle and why different rocks allow water through at different rates.
- Use evidence from an unfamiliar case to explain a cause-and-effect link and justify a suitable response.
Connect rock type to how it formed
Igneous rocks form when molten rock cools and crystallises. Granite cools slowly underground and has visible crystals; basalt cools more quickly after reaching the surface and has smaller crystals.
Sedimentary rocks form from deposited material that is compacted and cemented, or from chemical or biological material. The syllabus names limestone, sandstone and shale. Metamorphic rocks form when existing rock is changed by heat and pressure without fully melting; limestone can become marble and shale can become slate.
Follow the rock cycle as linked processes
Weathering breaks rock down in place; erosion removes material; transportation moves it; deposition or sedimentation lays it down. Burial can compact and cement sediment into sedimentary rock. Heat and pressure may transform existing rock; melting and later cooling allow crystallisation into igneous rock.
The rock cycle is not a fixed one-way loop. A rock can follow different pathways depending on uplift, exposure, burial, heat, pressure, melting and cooling.
Use permeability to explain water movement
Permeability is the ability of water to pass through pore spaces in rock or soil. In this syllabus, most sedimentary rocks such as limestone and sandstone are treated as permeable; igneous and metamorphic rocks, and some sedimentary rocks such as shale, are treated as impermeable.
Permeability describes connected spaces that let water pass. Do not confuse it with porosity alone: a rock may contain pores that are too small or disconnected for easy flow.
Sources for this lesson
Pause and explain
What process most directly turns loose sediment into sedimentary rock?
Worked example
A rock sample has large visible crystals and formed when molten rock cooled underground. Classify it and explain what happens if it later weathers, is transported and deposited.
Show the worked solution
- It is igneous rock; slow underground cooling allows crystals to grow.
- Weathering breaks material down, and erosion removes it from the original rock.
- If transported material is deposited, later compaction and cementation may form sedimentary rock.
Answer The sample is likely granite because it cooled slowly underground. The later sequence shows one possible route through the cycle toward sedimentary rock; it is not the only route.
Try a topic test
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A layer of shale is exposed, weathered and carried by a river. Explain the sequence and predict whether the original shale should let water pass through easily.
Give me a hint
Name the breakdown and movement processes before classifying the rock.
Compare my reasoning
- Weathering breaks the shale down; erosion removes it and transportation moves the particles.
- If the particles settle, deposition occurs; after burial, compaction and cementation can make sedimentary rock.
- The original shale is classified as impermeable in the syllabus, so water does not pass through it easily.
Weathering, erosion and transportation move the material; later deposition, compaction and cementation could form sedimentary rock. Shale itself is classed as impermeable.
Look for these in your work
- Processes distinguished
- Possible later formation explained
- Permeability classification correct
A student writes: 'All rocks become sedimentary before they can become igneous.' Correct the claim using two processes from the rock cycle.
Give me a hint
Show that several routes are possible and include melting or crystallisation.
Compare my reasoning
- Explain that different rocks can melt and then crystallise into igneous rock.
- Another route is weathering and erosion, followed by transport, deposition, compaction and cementation.
- Conclude that the cycle has multiple pathways rather than one required order.
The claim is false. A rock may melt and crystallise into igneous rock, while another path breaks down and deposits sediment that later compacts and cements. The rock cycle is not a single sequence.
Look for these in your work
- At least two routes described
- Crystallisation used correctly
- One-way claim rejected
A proposed water-storage site lies on sandstone in one area and shale in another. Explain one reason permeability matters and one additional piece of evidence needed before choosing.
Give me a hint
Connect water movement to a practical consequence, then name a limit of rock-type information.
Compare my reasoning
- Sandstone is classified as permeable, so water may move through connected spaces more readily.
- Shale is classified as impermeable, so it may restrict downward movement, although fractures and site conditions matter.
- A decision also needs evidence about fractures, soil, slope, water sources and engineering safety; rock type alone is not enough.
Permeability affects how readily stored water could leak through the ground. Sandstone is more permeable than shale in the syllabus classification, but fractures and local geology must be investigated before a site decision.
Look for these in your work
- Water movement linked to permeability
- Both classifications considered
- Site investigation limitation stated
Common mistakes
- Calling sedimentation the same process as cementation
- Assuming every rock follows one fixed route
- Treating permeability as identical to porosity
What can you explain now?
Which statement defines permeability?
Compare with the explanation
How readily water passes through connected pore spaces in rock or soil
The correct answer is “How readily water passes through connected pore spaces in rock or soil”. The alternatives “The percentage of a rock made of empty spaces” and “The speed at which magma cools” do not match the syllabus concept. Explain how the syllabus rocks form, how material moves through the rock cycle and why different rocks allow water through at different rates.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Name one example of each rock type, then describe one route through the rock cycle and explain permeability.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.