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Contents of 7.3 How do geologists determine the relative ages of rocks in widely separated places?

• The principle of lateral continuity states that sedimentary beds are continuously deposited over large areas until some sort of barrier limits their deposition.
• The principle of faunal succession states that fossil assemblages in rocks change through time as some species become extinct and new ones appear. Each species of organism has a limited time interval of existence. Fossil-bearing rocks are placed in relative-age progression by determining the interval of geologic time represented by the fossils that they contain.

7.3 How do geologists determine the relative ages of rocks in widely separated places?