The Rock Cycle

Rocks are made from many grains being joined together. As you know, rocks come in many shapes and sizes. The three main types of rock are:

  • Sedimentary
  • Igneous
  • Metamorphic

The rocks in the Earth are always changing due to the changes in the Earth, such as erosion. This is known as the rock cycle, which takes place over millions of years.

We will cover the rock cycle, which links all three types of rock. Below is the diagram of the rock cycle which shows sedimentary, igneous and metamorphic rock being weathered into sediment.

There are many different cycles within the rock cycle, so it is not just one big straightforward cycle, there are many loops within it.

Rock cycle Process

This process is described in the process of forming sedimentary rock. As you can see below, erosion consists of weathering and transportation.


1. Large rocks break up into smaller pieces (sediment) – This process is weathering

2. The pieces of broken rock get transported by wind, water, etc. – This process is transportation

  • In the rock cycle, the large rocks mentioned in the erosion process do not have to be sedimentary rock, they can also be igneous or metamorphic rock.


3. The pieces then settle in layers at the bottom of the ocean – This is called deposition.

Compaction and Cementing

4. The layers of sediment build up, which increases the pressure on the lower layers. The weight of the the layers above squash the sediment together – This process is known as compaction.

5. Sedimentary rock is formed as the sediment layers stick together – This process is called cementation.

  • This is the process in which the sediment forms sedimentary rock

Rocks may not stay in the form of sedimentary rock forever, as rocks are part of a cycle.

High Heat and Pressure

6. When sedimentary rock is under the conditions of high heat and pressure, it can form metamorphic rock.

  • Metamorphic rock can also go through weathering to turn into sediment, which will turn back into sedimentary rock.


7. When metamorphic rock melts, it turns into magma.


8. Magma can crystallise and turn into intrusive igneous rock. However, it could also become lava, which will crystallise to form extrusive igneous rock.

  • Crystallised magma forms igneous rock with large crystals and crystallised lava forms igneous rock with small crystals
  • The igneous rock can then go through weathering, which will lead to the formation of sedimentary rock

Sedimentary rock, metamorphic rock and igneous rock can all slowly uplift to the surface to undergo weathering.