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Half life dating methods

Then after another 5,000 years half of the remaining parent isotope will have decayed.

Index fossils are fossils that are known to only occur within a very specific age range.Typically commonly occurring fossils that had a widespread geographic distribution such as brachiopods, trilobites, and ammonites work best as index fossils.If the fossil you are trying to date occurs alongside one of these index fossils, then the fossil you are dating must fall into the age range of the index fossil. In a hypothetical example, a rock formation contains fossils of a type of brachiopod known to occur between 410 and 420 million years.The same rock formation also contains a type of trilobite that was known to live 415 to 425 million years ago.Since the rock formation contains both types of fossils the ago of the rock formation must be in the overlapping date range of 415 to 420 million years. There are two main methods determining a fossils age, relative dating and absolute dating.Relative dating is used to determine a fossils approximate age by comparing it to similar rocks and fossils of known ages.So, often layers of volcanic rocks above and below the layers containing fossils can be dated to provide a date range for the fossil containing rocks.The atoms in some chemical elements have different forms, called isotopes.These changes typically occur so slowly that they are barely detectable over the span of a human life, yet even at this instant, the Earth's surface is moving and changing.As these changes have occurred, organisms have evolved, and remnants of some have been preserved as fossils.

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