Rocks

The Formation of Sedimentary Rocks.

Compaction eventually forces the water out of the sediment.
Salts in the water crystallise under pressure
and cement the sediment particles together (like glue).
This is how sedimentary rock is made.

Crystalline Salt Cementing Rock Particles in Sedimentary Rock

How can Sedimentary Rocks be Identified?

Sedimentary rock is often formed in layers,
because the original sediment is laid down in layers.
This gives the rock a typical layered structure,
which can be seen in mudstone, and more clearly in shale.

Sedimentary rocks are often of a similar appearance
to the sediments which formed them (sandstone looks like sand!).

Fossils are only found in sedimentary rocks.

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