Presentation on theme: "Relative Dating. I. Relative Dating Relative Dating comparedRelative Dating is when you give the age of a rock or fossil compared to another rock or fossil."— Presentation transcript:
I. Relative Dating Relative Dating comparedRelative Dating is when you give the age of a rock or fossil compared to another rock or fossil. OLDER –Example: Rock A is OLDER than Rock B. –An actual age in years is not determined.
II. Rules of Relative Dating 1.Law of Superposition 1.Law of Superposition: When sedimentary rock layers are deposited, younger layers are on top of older deposits.
Rules of Relative Dating 2. Law of Original Horizontality 2. Law of Original Horizontality: Sedimentary rock layers are deposited horizontally. If they are tilted, folded, or broken, it happened later.
Rules of Relative Dating 3. Law of Cross-Cutting Relationships YOUNGER 3. Law of Cross-Cutting Relationships: If an igneous intrusion or a fault cuts through existing rocks, the intrusion/fault is YOUNGER than the rock it cuts through
III. Correlation matched up rocks and fossilsRock layers in different places and be correlated or matched up by matching up the rocks and fossils in the layers.
IV. Unconformity eroded missing sectionWhen rock has been eroded, so you have a missing section of time in the rock record.
Why are some of the layers tilted? What happened to the top of the folded rocks? The missing rock layers is called an __________.
What type of rocks formed above? What events might have caused the rock layers to become tilted? Why is the top flat? What caused the angular unconformity?
Index Fossils Some species of organisms only lived for a short period of time before they became extinct. If you use radiometric dating to get an age for the fossil, then you know that the rock the fossil is found in is also that age. Paleozoic Era Trilobite: Index fossil for the Paleozoic Era Age: 590-250 mya
Graptolite Ordovician PeriodIndex Fossil of the Ordovician Period Age: 500-335 myaAge: 500-335 mya
Fossil B lived 10 million years ago – 2 million years ago. Fossil A lived 20 million years ago- 8 million years ago. What do you know about the age of the rock containing both fossils?
What is B? Place the layers in order from oldest to youngest