Relative Age Dating

Question 1

Principle of original horizontality

Answer 1

Sedimentary layers are horizontal when they are originally deposited. Strata that are not horizontal have been deformed by movement of the earths crust

Question 2

Principle of faunal succession

Answer 2

Groups of fossil plants and animals occur in the geologic record in a definite and a determinable order

Question 3

Principle of crosscutting relations

Answer 3

Geologic features such as faults and igneous intrusions are younger than the rocks they cut

Question 4

Principle of inclusion

Answer 4

A rock body that contains inclusions of pre-existing rocks is younger then the rock from which the intrusions came from

Question 5

What is an unconformity

Answer 5

A period of time where deposition stopped

Erosion removed previously formed rocks and then the deposition resumed

Question 6

What is an angular unconformity

Answer 6

Rock layers found below a layer of younger sedimentary rock are tilted or folded

Question 7

Disconformity

Answer 7

Younger layers of sedimentary rock lie on top of older layers of flatline sedimentary rock that show signs of erosion

Question 8

Nonconformity

Answer 8

Sedimentary rock layers lie on top of an eroded surface

Question 9

Principle of superposition

Answer 9

In a sequence of undeforned sedimentary rocks the oldest beds are on the bottom and the youngest are on top

Question 10

What are the five principles

Answer 10

Original horizontality

Faunal succession

Cross cutting relations

Inclusion

Superposition