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.“If you’re trying to look at archaeological sites at the order of 30,000 or 40,000 years ago, the ages may shift by only a few hundred years but that may be significant in putting them before or after changes in climate,” he says.

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James Hutton and William Smith advanced the concept of geologic time and strengthened the belief in an ancient world.

For each dating or chronological method there is a link in the box at right to take you to that section of this page.

There, you will find a brief description of the method, plus links to take you to other webpages with more extensive information.

The clock was initially calibrated by dating objects of known age such as Egyptian mummies and bread from Pompeii; work that won Willard Libby the 1960 Nobel Prize in Chemistry.

But even he “realized that there probably would be variation”, says Christopher Bronk Ramsey, a geochronologist at the University of Oxford, UK, who led the latest work, published today in Science.Further, he proposed that wherever uncontorted 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.The Major Divisions of Geologic Time are shown here, arranged in chronological order with the oldest division at the bottom, the youngest at the top. Specifically, stratigraphy refers to the application of the Law of Superposition to soil and geological strata containing archaeological materials in order to determine the relative ages of layers.By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.But that assumes that the amount of carbon-14 in the atmosphere was constant — any variation would speed up or slow down the clock.Overview of Methods Superposition Stratigraphy Dendrochronology Radiocarbon C14 Radiometric Dating Methods Obsidian Hydration Dating Paleomagnetic/Archaeomagnetic Luminescence Dating Methods Amino Acid Racemization Fission-track Dating Ice Cores Varves Pollens Corals Cation Ratio Fluorine Dating Patination Oxidizable Carbon Ratio Electron Spin Resonance Cosmic-ray Exposure Dating This is an excellent overview of dating methodologies, and is a chapter in a textbook on Archaeology.