Earth Science

Earth History

Correlation Using Relative Ages

Study Tip
Think of correlation as a map making method. Explorers who want to map out the location of an unknown area need to take in account any significant features on the path that may give indication of their specific location. In a similar fashion, scientists look at specific clues to make their map for geologic history.

Correlation

  • Correlation is a method used to determine the age relationships between rocks that are not in the same local region.

Clues for Correlation

  • There are three kinds of clues that scientists look for when they want to figure out the relative age of a specific location.
Study Tip
Think of correlation as a map making method. Explorers who want to map out the location of an unknown area need to take in account any significant features on the path that may give indication of their specific location. In a similar fashion, scientists look at specific clues to make their map for geologic history.
  • Distinctive Rock Formations may be recognizable across multiple regions.
White Cliffs of Dover
The famous White Cliffs of Dover in southwest England can be matched to similar white cliffs in Denmark and Germany.
  • Index Fossils are fossils that are both widespread and only existed for a brief period of time, which allows us to determine the approximate age of the rock layer.
White Cliffs of Dover
Mucrospirifermucronatus is an index fossil that indicates that a rock was laid down around 416 to 359 million years ago.
  • Key Beds are recognizable layers of rock that are used in a similar manner like index fossils.
White Cliffs of Dover
The white clay is a key bed that marks the Cretaceous-Tertiary Boundary.
Concept Check
  • What is correlation, and what are the three types of correlation?