compaction and cementation
Oh no, what's happening now?
This might not be so bad after all - I'm feeling whole again.
As the layers of sediment build up, the pressure on the lower layers increases. The layers are squeezed together and any water mixed in with the sediments is forced out. This process is called compaction.
At the same time the particles of sediment begin to stick to each other - they are cemented together by clay, or by minerals like silica or calcite. This process is called cementation.
After compaction and cementation the sedimentary sequence has changed into a sedimentary rock. Sedimentary rocks like sandstone, shale and limestone differ from other rocks in that they:
- are formed from layers of sediment built up over many years
- are grains of sediment cemented together by various minerals
- may contain fossils - remains of plants and animals that were caught up in the sediment.
