The rock cycle is the continuous natural cycle in which igneous, sedimentary and metamorphic rocks change into one another through processes of weathering, deposition, compaction, pressure and heat.
Rocks are not permanent; over geological time they are constantly formed, broken down and reformed. The three main rock types are linked by processes that convert one into another, so that material may pass through each type many times over millions of years.
The three rock types
- Igneous rock: formed when molten magma or lava cools and solidifies, for example granite.
- Sedimentary rock: formed when weathered fragments are deposited, compacted and cemented, for example limestone.
- Metamorphic rock: formed when existing rock is altered by heat and pressure, for example marble.
Application
Understanding the rock cycle explains the properties of building stones.
| Rock | Origin | Typical use |
|---|---|---|
| Granite | Igneous | Hard-wearing cladding and paving |
| Limestone | Sedimentary | Facades and floors |
| Marble | Metamorphic | Decorative surfaces |
The origin of a stone determines its hardness, porosity and durability, which in turn govern where it can be used in construction. Weathering, which drives the cycle in nature, also affects how building stones age and erode over time.
Related terms
- natural stone
- granite
- limestone
- marble
- mineral
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