New carbon dating
Sometimes only one method is possible, reducing the confidence researchers have in the results. “They’re based on ‘it’s that old because I say so,’ a popular approach by some of my older colleagues,” says Shea, laughing, “though I find I like it myself as I get more gray hair.” Kidding aside, dating a find is crucial for understanding its significance and relation to other fossils or artifacts.In his process, an object is placed in a vacuum chamber and a supercritical fluid—a hybrid gas/liquid—is applied as a solvent (as in dry cleaning).Next, Rowe passes plasma—an "electrically excited ionized gas"—over the artifact, which selectively strips carbon from the sample.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.
For example, New Zealand’s massive Taupo volcano erupted in A. Relative chronology: Researchers have often constructed timelines of a culture or civilization based on the stylistic evolution of its decorative or dramatic arts — that’s why the method is also sometimes called stylistic seriation.
Methods fall into one of two categories: relative or absolute.