New dating methods

Before more precise absolute dating tools were possible, researchers used a variety of comparative approaches called relative dating.These methods — some of which are still used today — provide only an approximate spot within a previously established sequence: Think of it as ordering rather than dating.Thermoluminescence: Silicate rocks, like quartz, are particularly good at trapping electrons.Researchers who work with prehistoric tools made from flint — a hardened form of quartz — often use thermoluminescence (TL) to tell them not the age of the rock, but of the tool.Researchers can first apply an absolute dating method to the layer.They then use that absolute date to establish a relative age for fossils and artifacts in relation to that layer. Anything below the Taupo tephra is earlier than 232; anything above it is later.When it comes to determining the age of stuff scientists dig out of the ground, whether fossil or artifact, “there are good dates and bad dates and ugly dates,” says paleoanthropologist John Shea of Stony Brook University.The good dates are confirmed using at least two different methods, ideally involving multiple independent labs for each method to cross-check results.

The polarity is recorded by the orientation of magnetic crystals in specific kinds of rock, and researchers have established a timeline of normal and reversed periods of polarity.Egyptologists, for example, created a relative chronology of pre-pharaonic Egypt based on increasing complexity in ceramics found at burial sites.Whenever possible, researchers use one or more absolute dating methods, which provide an age for the actual fossil or artifact.Researchers can measure the amount of these trapped electrons to establish an age.But to use any trapped charge method, experts first need to calculate the rate at which the electrons were trapped.

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