The rock cycle and permeability Cambridge IGCSE Environmental Management revision
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In plain words
Rocks are not permanent. Over millions of years a mountain is worn down to sand, the sand becomes new rock, and that rock may be buried, cooked or melted and pushed back up. The endless recycling is called the rock cycle.
9 things to know
- Weathering is the breaking down of rock in the place where it stands, by the weather, by chemicals and by living things. Erosion is the wearing away and removal of the broken rock.
- Transportation is the carrying of the pieces by rivers, wind, ice or the sea. Deposition is the dropping of the pieces, which happens when whatever was carrying them loses energy.
- Sedimentation is the settling of the pieces in layers, usually under water.
- Compaction is the squeezing of the layers by the weight of the layers above, which pushes the water out. Cementation is when minerals form between the grains and glue them together. The result is sedimentary rock.
- Heat and pressure change any rock into metamorphic rock. If the rock gets hot enough to melt, it becomes magma.
- Crystallisation is the forming of crystals as magma or lava cools. It makes igneous rock.
- Any type of rock can become any other type. When buried rock is lifted back to the surface, weathering starts again.
- Permeability is how easily water can pass through the pore spaces, the tiny gaps, in rock or soil.
- Permeable rocks let water through: most sedimentary rocks, including limestone and sandstone. Impermeable rocks do not: igneous rocks, metamorphic rocks and some sedimentary rocks, such as shale.
Worked example
Describe how a piece of granite on a mountain top could become part of a sandstone.
- Weathering breaks the granite into small grains.
- The grains are eroded, and a river transports them downhill.
- Where the river slows, the grains are deposited and settle in layers. This is sedimentation.
- More layers bury them. Compaction squeezes the grains together and cementation glues them, forming sandstone.
Tips and tricks
- Weathering does not move anything. Once the pieces are carried away, you are describing erosion and transportation.
- Shale is the trap: it is a sedimentary rock, but it is impermeable.
It lands in your notebook with its questions as flashcards.
The rock cycle and permeability: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What is weathering?
Weathering breaks. It does not move.
Which process glues grains of sediment together?
Minerals form between the grains and act as glue.
Which of these rocks is permeable?
Most sedimentary rocks are permeable. Shale is the exception.
What forms when magma cools and crystals grow?
Crystallisation of molten rock makes igneous rock.
What turns a sedimentary rock into a metamorphic rock?
The rock changes without melting.
Why is sediment deposited where a river enters a lake?Stretch
A river with less energy cannot carry its load, so it drops it.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 7 marks. Write your answers on paper, then check them.
The rock cycle and permeability
Cambridge IGCSE Environmental Management 0680 · 7 marks · papermunch.org
Name ______________________________ Date ______________
Define the term permeability.[2]
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How easily water can pass through the pore spaces of rock and soil.
Describe how layers of sediment become sedimentary rock.[3]
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More sediment is deposited on top. Its weight compacts the layers and squeezes out the water. Minerals form between the grains and cement them together.
Explain why a reservoir built on granite loses less water than one built on sandstone.[2]
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Granite is impermeable, so water cannot pass through it. Sandstone is permeable, so water drains away through its pore spaces.
Answers: The rock cycle and permeability
- 1. How easily water can pass through the pore spaces of rock and soil.
- 2. More sediment is deposited on top. Its weight compacts the layers and squeezes out the water. Minerals form between the grains and cement them together.
- 3. Granite is impermeable, so water cannot pass through it. Sandstone is permeable, so water drains away through its pore spaces.