1. Relative Age Relationships
Steno’s Laws
Relative Age Relationships

2. Nicolas Steno Born in Copenhagen The son of a goldsmith
Considered by some of father of geology and stratiography

3. Early Questions
He was brought a shark head for autopsy and noticed that the shark’s teeth resembled the “stony tongue” rocks he had found embedded in other rocks. This caused him to be curious about the solids within solids he had found.

4. Findings
Steno was not only interested in “fossils as we would define them today, but minerals, crystals, incrustations, veins, and even entire rock layers or strata.”
He assumed that “all rocks and minerals had once been fluid, Steno reasoned that rock strata and similar deposits were formed when particles in a fluid such as water fell to the bottom.”

5. Relative Age
To Steno, the deeper the rock layer, the older its origin and vise versa.
If fossils were found in that layer it presented a type of timeline of the organisms that existed at that time.

6. Law of Superposition
Basically stated: the oldest layer will lie below or underneath the youngest.

7. Law of Original Horizontality
Sedimentary rocks are originally deposited lying flat
Later undergo tilting or folding

8. Law of Cross Cutting
If a rock layer is cut by a fault or igneous intrusion, the rock that is cut must be older than the layer that cuts it.
Layers are older than the rock that cuts them.

9. Law of Lateral Continutity
Rock layers will extend outwards until they grade into those produced in adjacent environments.

10. Conclusions
All that is needed to find the relative age of a rock layer is its original position.
To know the original position you must first assume how the layer was folded, in what directions, and any other factors that can be seen.