Rocks are made up of many mineral grains that have fused together. They come in many forms and sizes.
The rocks on the Earth are always changing due to geological processes, such as 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.
A part of the cycle is covered in ‘How Sedimentary Rocks Form‘, but here we’ll go into more detail.
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, large rocks that undergo erosion can be any rock type, including sedimentary, igneous, and metamorphic rocks.
3. The pieces then settle in layers at the bottom of the ocean – This is called deposition
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 are the processes that turn sediment into sedimentary rock
6. When sedimentary rock is under conditions of high heat and pressure, it can transform into metamorphic rock.
Metamorphic rock can undergo erosion to become sediment once again. Eventually, this will form 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.
The igneous rock can then go through weathering, which will lead to the formation of sedimentary rock. However, Sedimentary rock, metamorphic rock and igneous rock can all slowly uplift to the surface to undergo weathering.