Rocks and the rock cycle
Use processes to explain how one rock type can become another.
Before you begin
- Solids and melting
- Weathering as breakdown
Identify how a rock forms
Igneous rock forms when molten material cools and solidifies. Sedimentary rock can form as deposited fragments are compacted and cemented, although some form by chemical or biological processes. Metamorphic rock forms when existing rock changes under heat and pressure without completely melting. Classify by formation process rather than colour alone.
Trace more than one pathway
The rock cycle has many routes and no compulsory starting point. Weathering breaks rock down, erosion transports the fragments, and deposition leaves them elsewhere. Burial may lead to sedimentary rock or metamorphism; melting followed by cooling can form igneous rock. These processes operate over different timescales, and a rock need not pass through every type.
Worked example
Granite is broken into grains, which are transported, deposited, compacted and cemented. What kind of rock can form?
Show the worked solution
- Granite fragments become sediment through breakdown and transport.
- Deposition gathers the grains in a new location.
- Compaction and cementation bind the grains into rock.
A sedimentary rock.
Try it yourself
Which process forms metamorphic rock?
Common mistakes
- Do not confuse weathering, which breaks rock down, with erosion, which transports material.
What can you explain now?
Can an igneous rock become metamorphic without first becoming sedimentary? Explain.
Compare with the explanation
Yes, through sufficient heat and pressure without complete melting.
The rock cycle is a network of possible pathways. A sedimentary stage is not a required step between all other rock types.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Original StudyForA content. AI-assisted checks completed; subject-teacher review is still pending. These lessons are not endorsed by an exam board.
NGSS science topic progressions ↗