1. Earth Systems 3209
Unit 2: Relative Dating

3. relative dating 6 Major Types: Superposition Horizontality
Cross-cutting relations
Inclusions
Unconformities
Fossils

4. Cross sectional layering
Used to show a 2D image of the layers of rock in the crust
Used in determining
relative dating

5. 1. Law of Superposition Book and cylinder demos
In an undeformed sequence of sedimentary rock, each bed is older than the one above and younger than the one below.
*The youngest is always on top

6. 2. Principal of original Horizontality
states that most layers of sediment are deposited in a horizontal position.
If rock layers are folded or inclined, then the layers must have been moved
into that position by crustal
disturbances. (folding/faulting)

7. Faulting and Folding
When pressure (compressional or tensional forces) has been added to rocks.
depending on the type and environment, they may break or bend.

8. Faulting and Folding
Faulting – Movement of rock units along a crack in the rock.
The fault below is caused by compressional forces.

9. Faulting and Folding
Folding – Bending of rock units caused by compressional forces, as seen below.

11. 3. Cross-cutting relations
Book demo
An igneous rock is younger than the rock strata (or beds or layers) that it cuts across.
A geological feature such as a fault is younger than the rock strata (or beds or layers) that it cuts across.

12. Label the two types of Cross Cutting in the following diagram.

13. Order the layers from oldest to youngest

14. Contact Metamorphism
When molten rock comes into contact with older rock
the heat causes a kind of baking that changes the original rock.
Often represented as x’s on diagrams

15. Contact Metamorphism

16. Group work
Practice questions