What are sedimentary rocks made of?

Sedimentary rocks are made of minerals and debris that have been weathered or eroded from rocks over long stretches of time. This sediment can be laid down by water, by the movement of earth or glaciers, by evaporation or by biological processes.

After they are laid down, water is compressed from the sediment, and other processes change it into hard but brittle rock. Some types of sedimentary rock form in the ocean and are known as marine deposits, while those that form on earth are called terrestrial deposits. Clastic rocks are grouped by the size of their grain, while biochemical and chemical rocks such as limestone are classified by their chemistry.