Geologic Time

long period when deposition stopped, erosion removed previously formed rocks,then resumed

establishing the equivalence of rocks of similar age in different area

The principle that states: layers of sediment are generally deposited in a horizontal position.

each bed is older than the one above it and younger than the one below it.

Records Earth's History

during the pause in deposition, a period of deformation (folding, tilting) and erosion occurred

tells us the sequence in which events occurred, not how long ago they occurred.

separates older metamorphic or intrusive igneous rocks from younger sedimentary rocks

a fault cuts through rock layers, the fault or intrusion is younger than the rocks affected.

Forces and processes we observe today have been at work for a long time

when two sedimentary rock layers are separated by an erosional surface.

Rock contained within other rocks