Transcript Age Dating

Geologic Time
Using the rock record to age date rock
layers
Age Dating
 Geoscientists have devised a set of laws to
help us understand (the “It’s so obvious”
Laws)
Age Dating
Uniformitarianism- Earth’s processes have
remained the same over time
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(rock cycle, water cycle, climate, etc.)
If you know how a rock formed 1 million
years ago…
then you know how the same type of rock
formed 3 billion years ago
Age Dating
 Stratification
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rocks form in layers or strata
By looking at the surrounding layers,
geoscientists can infer the relative age of a
rock layer.
Relative Age Dating
 Law of Superposition
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oldest rocks on the bottom
Age Dating
 Law of Original Horizontality
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layers originally deposited horizontally
If they are folded or tilted…
Then they have been disturbed
Age Dating
 Law of Cross-cutting
Relationships
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rock/faults that cut through rock layers must
be younger than the layers
Age Dating
 Principle of Fossil Succession
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fossils succeed each other in a definite
order