What is relative dating

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William Smith's collecting and cataloging fossil shells from rocks led to the discovery that certain layers contained fossils unlike those in other layers (see: fossil sorting).Using these key or index fossils as markers, geologists began to identify a particular layer of rock wherever it was exposed.For example, it is believed that during a particular episode the land surface was raised in one part of the world to form high plateaus and mountain ranges.After the uplift of the land, the forces of erosion attacked the highlands and the eroded rock debris was transported and redeposited in the lowlands.Relative dating is a dating method that used to determine determine the relative ages of geologic strata, artifacts, historical events, etc.

Similarly, dendrochronology measures the tree rings in trees and assumes they represent years.Hutton, a Scottish geologist, first proposed formally the fundamental principle used to classify rocks according to their relative ages.He concluded, after studying rocks at many outcrops, that each layer represented a specific interval of geologic time.During the same interval of time in another part of the world, the land surface subsided and was covered by the seas.With the sinking of the land surface, sediments were deposited on the ocean floor.

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