Rock Layers

Compaction

• Happens when pressure is applied to a material (over long periods of time)

Cementation• Involves the deposition of a cementing

matrix in the pore spaces between the grains of sediment

Before cementation(notice the air spaces)

horizontal

• Level- like a floor

• Not higher on one side or the other

Principle of Original Horizontality

• Each new deposit of sediment forms a new horizontal layer on top of the layer below

• PRINCIPLE OF ORIGINAL HORIZONTALITY • • Sedimentary and extrusive igneous rocks are

originally laid down in horizontal layers • • any change from that is viewed as a disturbance

of those layers (something happened later) • folding, tilting (occur during mountain-

building events, for example)• sedimentary and igneous extrusive rocks that are folded

or tilted must have first been deposited in horizontal layers before being folded or tilted.

•  • 1. layer deposited• 2. layer deposited• 3. layer deposited• 4. all three layers are tilted 

Label the above (1-4)

Uniform

• The way things happen today is the same way things have always happened

Uniformitarianism

• Means that the present is the key to the past

http://sln.fi.edu/fellows/payton/rocks/create/sediment.htm

Sedimentary Rock