G10: The Rock Cycle
The continuous cycle of rock transformation between igneous, sedimentary and metamorphic rocks, driven by Earth's internal and external processes.
The Rock Cycle
The continuous cycle of rock transformation between igneous, sedimentary and metamorphic rocks, driven by Earth's internal and external processes.
Key Fact: The rock cycle is a continuous process where rocks are transformed between igneous, sedimentary and metamorphic types
Key Fact: Igneous rocks form from cooling magma/lava; weathering and erosion break them into sediment then sedimentary rocks
Key Fact: Sedimentary rocks can be metamorphosed by heat/pressure to metamorphic rocks; or melted to magma then igneous rocks
Key Fact: Metamorphic rocks can be weathered/eroded to sedimentary rocks; or melted to magma then igneous rocks
Key Fact: Driving forces: internal (heat from Earth's core drives melting, metamorphism, tectonics) and external (the Sun drives weathering, erosion, transport, deposition)
Key Fact: The rock cycle operates over millions of years and is evidence that Earth is a dynamic system
📋 Key Vocabulary and Concepts
For The Rock Cycle, you must know:
- Weathering: The in-situ breakdown of rock at or near the Earth's surface by physical, chemical or biological processes
- Erosion: The removal and transport of weathered rock material by agents such as water, wind, ice or gravity
- Uplift: The upward movement of rocks from depth to the Earth's surface, caused by tectonic forces or isostatic rebound
- Protolith: The original parent rock before metamorphism (e.g. limestone is the protolith of marble)
- Diagenesis: Low-temperature physical and chemical changes to sediment after deposition, prior to full lithification
❓ Practice Questions
Q: Describe a complete path through the rock cycle starting from an igneous rock.
Q: What are the two main energy sources driving the rock cycle?
Q: Can a metamorphic rock become a sedimentary rock directly?
Q: How does subduction return rocks to the mantle?
Q: Why is the rock cycle described as a 'cycle' when not all paths are circular?
✅ Answers
- Granite (igneous) to weathering/erosion to sediment transport to deposition to compaction and cementation to sandstone (sedimentary) to heat and pressure to quartzite (metamorphic) to further heating/melting to magma to cooling/crystallisation to granite (igneous again).
- Internal heat from Earth's core (drives melting, metamorphism, plate tectonics, volcanism) and external solar energy (drives weathering, erosion, transport, and deposition by water, wind and ice).
- Yes, metamorphic rocks exposed at the surface can be weathered and eroded into sediment, which is then transported, deposited and lithified into sedimentary rock.
- Oceanic crust (including any sedimentary or igneous rocks on it) is subducted at convergent boundaries, sinking into the mantle where it may melt, becoming magma that can rise to form new igneous rock, completing part of the cycle.
- It is a cycle because rocks can be continuously transformed between the three types, but it is not a simple circle. Rocks can take many different paths (e.g. igneous to metamorphic to igneous without becoming sedimentary). It is a network of interconnected processes rather than a single loop.
🎯 Exam Tips
- Know ALL possible paths between the three rock types, not just one circular route
- External processes (Sun-driven): weathering, erosion, transport, deposition
- Internal processes (core heat-driven): melting, metamorphism, tectonism, uplift
- Be able to trace a specific path (e.g. from sedimentary to igneous)
📝 Exam Technique
GCSE Geology Exam Tips — The Rock Cycle:
1. For The Rock Cycle questions, use correct geological terminology and classify features precisely
2. Reference specific geological time periods and processes
3. When interpreting data, consider the quality and limitations of the evidence
4. Apply your understanding of The Rock Cycle to fieldwork observations and map data
5. For evaluation, weigh competing geological theories with evidence
1. For The Rock Cycle questions, use correct geological terminology and classify features precisely
2. Reference specific geological time periods and processes
3. When interpreting data, consider the quality and limitations of the evidence
4. Apply your understanding of The Rock Cycle to fieldwork observations and map data
5. For evaluation, weigh competing geological theories with evidence
⚠️ Common Errors
✗ The rock cycle always goes igneous to sedimentary to metamorphic to igneous ✓ The rock cycle has many possible paths; rocks can go directly from igneous to metamorphic, or sedimentary to igneous, etc. It is a network, not a single loop
✗ Once a rock becomes metamorphic it cannot become sedimentary ✓ Any rock at the surface can be weathered and eroded, metamorphic rocks exposed by uplift can become sediment just like any other rock type
✗ Weathering and erosion are the same process ✓ Weathering is the in-situ breakdown of rock; erosion is the removal and transport of the broken material, they are different processes
✍️ Model Answer
Full-Mark Response
Describe the rock cycle and explain the processes that transform rocks from one type to another. [6 marks]
The rock cycle describes the continuous transformation of rocks between three types: igneous, sedimentary and metamorphic. Igneous rocks form when magma or lava cools and crystallises. At the surface, weathering breaks them down, erosion removes the debris, and rivers, wind or ice transport and deposit the sediment. Through compaction and cementation (lithification), sediment becomes sedimentary rock. If sedimentary rock is subjected to heat and/or pressure through burial or tectonic activity, it metamorphoses into metamorphic rock. Metamorphic rock can be further heated until it melts, becoming magma that cools to form new igneous rock. Alternatively, any rock type exposed at the surface can be weathered and eroded back into sediment. The cycle is driven by two energy sources: internal heat from Earth's core (driving melting, metamorphism, magma generation, tectonic uplift) and external solar energy (driving weathering, erosion, transport and deposition). The rock cycle is not a simple loop but a network, rocks can follow many paths. For example, igneous rock can go directly to metamorphic without becoming sedimentary, or sedimentary rock can melt directly to become igneous. Subduction returns crustal material to the mantle, where it may be recycled into new magma, completing the longest-timescale part of the cycle.
📊 AO Deep Dive
Assessment Objective Analysis
AO1 (Knowledge & Understanding): Demonstrate knowledge and understanding of the rock cycle, including key geological concepts, observational data and theoretical models relevant to OCR J357.
AO2 (Application of Knowledge): Apply knowledge and understanding of the rock cycle to both familiar and unfamiliar geological contexts, using field evidence and theoretical principles to explain phenomena.
AO3 (Analysis & Evaluation): Analyse geological data related to the rock cycle, evaluate evidence from observations and investigations, and construct reasoned arguments using scientific methodology.
📝 Exam Questions by Topic
🎬 Video Resources
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