Sedimentary Rocks

The three main types of rock are:

  • Sedimentary
  • Igneous
  • Metamorphic.

Sedimentary rocks are formed by joining many broken remains of other rocks together. Some examples of sedimentary rocks are conglomerate, mudstone and limestone.

As bits of minerals settle into layers over thousands of years, the weight of water and the layers of sediment above press down and cement the minerals into sedimentary rock

How Sedimentary Rocks Form

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

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

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

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

4. The weight of the water and layers of sediment above squash the sediment below – This process is known as compaction.

5. Sedimentary rock is formed as the sediment layers stick together – 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 might look like:

You can clearly see the layers of sediment, compacted and built up over time.

As the layers of sediment build up, fossils can be found in sedimentary rock. This is because dead organisms settle between the layers.

Ammonite fossil