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Rock Factory
Cambridge IGCSE Environmental Management 0680 EXAM YEARS 2027-2029 Sedimentary rocks
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How sedimentary rocks form
This free game is part of our Cambridge IGCSE Environmental Management (0680) course for exams in EXAM YEARS 2027-2029.
What are sedimentary rocks?
Sedimentary rocks are made from sediment: fragments of older rock, the remains of living things, or minerals left behind by water. They form slowly, in layers, at low temperatures near the Earth's surface.
In Rock Factory, you follow a chunk of mountain on its 90-million-year journey to becoming sedimentary rock. In each chapter you predict what happens next, then watch it play out in 3D.
The six steps of sedimentary rock formation
- Weathering: rock is broken down where it is, by physical, chemical or biological processes.
- Erosion: the broken pieces are worn away and removed.
- Transportation: rivers, wind, ice and the sea carry the sediment. The further it travels, the smaller and more rounded it becomes.
- Deposition: the sediment settles out, usually in lakes and seas. Heavier particles settle first.
- Compaction: new layers press down on older ones, squeezing out water.
- Cementation: dissolved minerals crystallise between the grains and glue them together.
Layers and fossils
Sedimentary rocks form in layers called strata. New layers are laid on top of old ones, so the lower layers are usually older. Sedimentary rocks are also where we find fossils, because plant and animal remains are buried gently without being melted. The chalk of the White Cliffs of Dover is made from the skeletons of tiny sea creatures.
Types of sedimentary rock
- Clastic (made from rock fragments): conglomerate, sandstone, shale and mudstone.
- Chemical (left behind when water evaporates): rock salt.
- Organic (made from the remains of living things): chalk and coal.
Exam tips
- Don't mix up the rock types: cooling magma makes igneous rock, heat and pressure make metamorphic rock.
- Well-rounded grains in a rock are a clue that the sediment travelled a long way.
- Learn the six steps in order. They are often asked as a sequence or a flow diagram.
Frequently asked questions
How are sedimentary rocks formed?
Through weathering, erosion, transportation, deposition, compaction and cementation. Sediment builds up in layers, is squeezed, and is then glued together by minerals.
Why are fossils found in sedimentary rocks?
Sedimentary rocks form at low temperatures, so the remains of plants and animals are buried without being destroyed. Igneous rocks form from melted rock, which destroys any remains.
What are examples of sedimentary rocks?
Sandstone, conglomerate, shale, mudstone, chalk, coal and rock salt.
What is the difference between compaction and cementation?
Compaction is when the weight of new layers squeezes sediment together and pushes out water. Cementation is when dissolved minerals crystallise between the grains and glue them together.
Is Rock Factory free?
Yes. The game is free to play in your browser, with no sign-up. It covers rocks and minerals in the Cambridge IGCSE Environmental Management course.