Despite seeming like a relatively stable place, the Earth's surface has changed dramatically over the past 4.6 billion years.

Mountains have been built and eroded, continents and oceans have moved great distances, and the Earth has fluctuated from being extremely cold and almost completely covered with ice to being very warm and ice-free.

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This term means that older artefacts are usually found below younger items.

Absolute dating is the process of determining an age on a specified chronology in archaeology and geology.

Radiocarbon dating involves determining the age of an ancient fossil or specimen by measuring its carbon-14 content.

Carbon-14, or radiocarbon, is a naturally occurring radioactive isotope that forms when cosmic rays in the upper atmosphere strike nitrogen molecules, which then oxidize to become carbon dioxide.

Particular isotopes are suitable for different applications due to the type of atoms present in the mineral or other material and its approximate age.

For example, techniques based on isotopes with half lives in the thousands of years, such as Carbon-14, cannot be used to date materials that have ages on the order of billions of years, as the detectable amounts of the radioactive atoms and their decayed daughter isotopes will be too small to measure within the uncertainty of the instruments.Coins found in excavations may have their production date written on them, or there may be written records describing the coin and when it was used, allowing the site to be associated with a particular calendar year.In historical geology, the primary methods of absolute dating involve using the radioactive decay of elements trapped in rocks or minerals, including isotope systems from very young (radiocarbon dating with Radiometric dating is based on the known and constant rate of decay of radioactive isotopes into their radiogenic daughter isotopes.After death the amount of carbon-14 in the organic specimen decreases very regularly as the molecules decay.When museums and collectors purchase archaeological items for their collections they enter an expensive and potentially deceptive commercial fine arts arena.In archaeology, absolute dating is usually based on the physical, chemical, and life properties of the materials of artifacts, buildings, or other items that have been modified by humans and by historical associations with materials with known dates (coins and written history).