Dating methods in history
Measuring carbon-14 in bones or a piece of wood provides an accurate date, but only within a limited range.Says Shea: “Beyond 40,000 years old, the sample is so small, and the contamination risk so great, that the margin of error is thousands of years.This includes factoring in many variables, such as the amount of radiation the object was exposed to each year.These techniques are accurate only for material ranging from a few thousand to 500,000 years old — some researchers argue the accuracy diminishes significantly after 100,000 years.Thermoluminescence: Silicate rocks, like quartz, are particularly good at trapping electrons.
Both methods date rock instead of organic material. But unlike radiocarbon dating, the older the sample, the more accurate the dating — researchers typically use these methods on finds at least 500,000 years old.Both plants and animals exchange carbon with their environment until they die.Afterward, the amount of the radioactive isotope carbon-14 in their remains decreases.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.Paleomagnetism is often used as a rough check of results from another dating method.