The Rock Cycle

Rocks are made up of many mineral grains that have fused together. They come in many forms and sizes.

The rocks on Earth are constantly changing due to geological processes like erosion and weathering. This is known as the rock cycle, which takes place over millions of years.

Let’s look at the rock cycle, which connects the three main rock types: sedimentary, igneous, and metamorphic.

  • There are many different stages and processes within the rock cycle.

Rock Cycle Process

Part of the cycle is covered in ‘How Sedimentary Rocks Form‘, but here we’ll go into more detail.

Erosion

The process of erosion involves weathering and transportation (steps 1 and 2)

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

2. The pieces of broken rock get transported by natural forces, such as wind and water – This process is transportation

In the rock cycle, rocks that undergo erosion can belong to any of the three main types: sedimentary, igneous or metamorphic.

Deposition

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

Compaction and cementation

4. The layers of sediment build-up, which increases the pressure on the lower layers. The weight of the layers above squashes 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.

Compaction and cementation together transform sediment into sedimentary rock.

High heat and pressure

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

Metamorphic rocks can also undergo erosion, turning back into sediment that will eventually form sedimentary rocks again.

Melting

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

Crystallisation

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, while crystallised lava forms igneous rock with smaller crystals.

The igneous rock can then go through weathering, which will lead to the formation of sedimentary rock. However, sedimentary, metamorphic, and igneous rocks can all gradually rise to the Earth’s surface to undergo weathering.