Relative and Absolute AgeLaw of Superposition
Relative and Absolute Dating
There are two major ways to date geologic events:
Relative dating-how old a rock is compared to surrounding rocks
Absolute dating-actual number of years since the rock was formed
Relative Dating
The various relative dating methods tell you whether a specific rock or layer of rocks is younger or older as compared to surrounding rocks
This type of dating does not give an exact age for the rock
• The Law of Superposition states that in an undisturbed sequence of sedimentary rock:Each layer is older than the one aboveEach layer is younger than the one below
Law of Superposition
• a vertical set of strata (layers) is a chronological record of the geologic history of that strata
• Youngest layers are on top and oldest on bottom
Law of Superposition
• Absolute Dating
– Absolute dating can give you the exact age of a rock
– This is accomplished using radioactive dating, which is also referred to as radiometric dating
– Based on the regular radioactive decay of certain elements
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