Relative Dating and Superposition
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Objective
I can explain how the law of superposition helps determine the relative ages of rocks and fossils.
Part 1 of 4
Warm-up video
Khan Academy · 4:35Vetted channel
We don't generate video — this one is by Khan Academy on YouTube. The practice questions and exit ticket below were drafted by AI for this objective, and every question is editable in the teacher guide.
Part 2 of 4
Key concepts
3 concepts
- 1
The geologic time scale divides Earth's history into units called eons and eras, which are mapped out using clues found in rocks.
- 2
The law of superposition states that in undisturbed rock layers, the layers at the bottom are older than the layers at the top.
- 3
The law of cross-cutting relationships helps determine relative ages when an igneous intrusion or fault cuts through existing rock layers.
Part 3 of 4
Practice
10 questions
What does the law of superposition help scientists figure out?
Imagine you have a stack of books. The bottom book has a copyright date of 1990, and the top book has a copyright date of 2020. Which book is older?
Part 4 of 4
Exit ticket
Quick comprehension check
“Imagine you find two layers of rock. Layer A is on the bottom, and Layer B is on top. According to the law of superposition, which layer is older?”
Sample answer included in the free materials
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Teacher Guide
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