Relative dating wikipedia horse dating online

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.

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From the results of studies on the origins of the various kinds of rocks (petrology), coupled with studies of rock layering (stratigraphy) and the fossils they contain (paleontology), geologists have associated layers of rocks with sequence of events thought to have occurred over hundreds of millions of years.

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.

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).

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.

Between the years of 17, James Hutton and William Smith advanced the concept of relative dating.

Hutton, a Scottish geologist, first proposed formally the fundamental principle used to classify rocks according to their relative ages.

Dendrochronology is a technique of dating past climatic changes through a study of tree ring growth.

Each year a tree adds a layer of wood to its trunk and branches thus creating the annual rings we see when viewing a cross section.

By allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change.

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