4 relative dating principles

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.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).Geologists employ a handful of simple principles in relative age dating; two of the most important of these are are the principles of Just as uniformitarianism is the key underlying assumption of geology, the science's most fundamental principle is superposition, developed by Danish anatomist Nicholas Steno (1638-1686) in the 17th century.is simple, intuitive, and is the basis for relative age dating.

But, before that, they relied upon a different approach to first determine the sequence of important events in Earth's past: Relative age dating has to do with determining the temporal ordering of events in Earth's past.By using dendrochronology scientists have dated certain living trees to having ages of around 4600 years.It may surprise you to learn that geologists were able to determine much of the history of the Earth and its life without knowing anything about the actual ages of the rocks that they studied.Uniformitarian geologists began using the principles of stratigraphy to assign dates to the layers of the geological column fossils back in the late 1700s.Relative dating uses a combination of fossil studies and structural interpretation to draw conclusions about the geological history of an area.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.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.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.

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