Sedimentary Rocks

The three main types of rock are:

  • Sedimentary
  • Igneous
  • Metamorphic

Sedimentary rocks form by the accumulation and compaction of broken fragments from other rocks. Some examples of sedimentary rocks are conglomerate, mudstone and limestone.

Over thousands of years, as mineral particles settle into layers, the weight of the overlying water and sediment compresses them, leading to the formation of sedimentary rock.

How Sedimentary Rocks Form

1. Large rocks break into smaller pieces, known as sediment – This process is called weathering.

2. Natural forces like wind and water transport the broken rock pieces – This process is called transportation.

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

3. The pieces settle in layers at the bottom of bodies of water, such as oceans – This process is called deposition.

4. The weight of the water and layers of sediment above compresses the layers below – This process is called compaction.

5. The layers of sediment bind together to form sedimentary rock – This process is called cementation.

Here is the order of the whole process to form sedimentary rocks:

1) Weathering2) Transportation3) Deposition4) Compaction5) Cementation

This is what sedimentary rock can look like:

You can see the visible layers of different colours and textures, which shows the different types of sediment. The surface of the rock may be rough or smooth, depending on the type of sediment that formed it.

sedimentary rocks may contain fossils, as dead organisms can become trapped between the layers of sediment during its formation.