Relative age and relative dating
Wide rings are produced during wet years and narrow rings during dry seasons.This technique has posed a different problem for creationists, as this dating method does not make use directly of accelerated decay.Geologists have divided the Earth's history into Eras -- broad spans based on the general character of life that existed during these times -- and Periods -- shorter spans based partly on evidence of major disturbances of the Earth's crust.The "relative" positions of layers and fossils to assign estimated dates to strata.Often when geologists examine rock outcrops like the one illustrated above they are interested in not only the types of rocks present, but the order in which they formed.When they put events in chronological order like they use Relative Dating.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.During the same interval of time in another part of the world, the land surface subsided and was covered by the seas.
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.
Further, he proposed that wherever un-contorted layers were exposed, the bottom layer was deposited first and was, therefore, the oldest layer exposed; each succeeding layer, up to the topmost one, was progressively younger.
It only sequences the age of things or determines if something is older or younger than other things.
Some types of relative dating techniques include climate chronology, dendrochronology, ice core sampling, stratigraphy, and seriation.Therefore, the actual length of geologic time represented by any given layer is usually unknown or, at best, a matter of opinion.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).The same thing can be done with geologic features in a rock outcrop.