Foundational Concepts
Dating Methods
Relative Dating
Absolute Dating
Paleomagnetics
Geologic Time
Earth Processes
Life Processes
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Introduction to Dating Methods
Dating the age of rocks is critical to reconstructing Earth's history. Geologists rely on two basic types of dating: absolute dating and relative dating. Absolute dating establishes how many years ago a given event took place. The most important methods of absolute dating are based on the decay of naturally occurring radioactive elements. Relative dating places historical events in their correct order but does not yield numerical estimates of how many years ago the events happened. It may seem odd that the two procedures are kept distinct—if scientists can determine the numerical ages of rocks and fossils they should be able to put the evidence of ancient life in the correct historical order. The problem is that only some types of rocks and fossils can be numerically dated, so all other evidence of ancient life must be related to age-dated material by the techniques of relative dating.

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