Sedimentary Rocks


Sediment: means small pieces of rock

Formed by weathering, erosion and deposition.

o       Weathering: the breaking down of rocks and other materials on Earths surface      

          (caused wind and water)

o       Erosion: The moving of materials caused by weathering

o       Deposition: The process where sediments that were carried by erosion are put in a new     location. (Usually involves compacting and cementing of many materials together)


Sedimentary rocks are classified by the composition of the materials in them. 


There are three main categories:


     Clastic Rocks: made from fragments of existing rocks and the size and shape of those        pieces.  They are cemented together with clay, mud or sand.

Sandstone: made from sand-sized pieces

Shale: dust sized fragments (with mud or clay)

(If over of the rock is made of pebbles, the rock is a conglomerate. Puddingstone is      an example of a conglomerate.


Organic Rocks: made from organisms that were once living.

Organic means living

Many were formed from shells of crustaceans and microorganisms.

Limestone, and coral reefs are examples

Chalk is a type of fine-grained limestone.

Coal is another example


Chemical Rocks: formed when seas dried up, leaving minerals dissolve in the water.

Some Limestone forms this way.

Rock salt and Gypsum are other examples.