What steps led to this rock formation?
What do you see? The rock is a sandstone, so first there were rocks that weathered and eroded. The cross-bedding indicates that the sand was deposited in a dune. The sand was then buried deeply enough that it turned into rock. This concept will explore how something like sand could become a rock.
Sedimentary Rock Formation
Accumulated sediments harden into rock by lithification, as illustrated in the Figure below. Two important steps are needed for sediments to lithify.
- Sediments are squeezed together by the weight of overlying sediments on top of them. This is called compaction. Cemented, non-organic sediments become clastic rocks. If organic material is included, they are bioclastic rocks.
- Fluids fill in the spaces between the loose particles of sediment and crystallize to create a rock by cementation.
The sediment size in clastic sedimentary rocks varies greatly (see Table in Sedimentary Rocks Classification).
This cliff is made of sandstone. Sands were deposited and then lithified.
- Sedimentary rocks are made of fragments of older rocks or pieces of organisms.
- Compaction and cementation lead to lithification of sedimentary rocks.
- Compaction is the squeezing of sediments by the weight of the rocks and sediments above them. Cementation is when cement from fluids bind sediments together.
- How does compaction lead to lithification?
- How does cementation lead to lithification?
- What is the difference between clastic and bioclastic sedimentary rocks?
Use this resource to answer the questions that follow.
- Describe the first step of lithificsation.
- What happens when the water is pushed out?
- What is the material located between the mineral grains called?