For an explanation, see the main splats page
SPLATS about dating methods
The principles of dating methods
- Dating takes two forms: it can deliver an absolute age in years or an age relative to other events. Relative dating is sometimes all that is available to us.
- All geological dating methods come with a small amount of uncertainty, because they rely on probabilities and inference, based on the best available data.
- Some dating methods can be interfered with by contamination of the sample, but combining several methods can help avoid the risk of error from this source.
- The oldest fossil traces we know of go back to about 3800 million years, but as most rocks of that age have been since destroyed, life may be a little older.
- In 1920, Andrew Douglass suggested dendrochronology, using tree rings to build a sequence of years, and using other timber with overlaps to extend the scale.
- Dendrochronology can be used to date artefacts very accurately for thousands of years, relying on unique patterns that can be traced from one tree to another.
- In 1947, Willard Libby introduced the idea of carbon-14 dating. By 1949, he could present carbon dating as a fully developed technique, ready to use.
- Material less than 50,000 years old can be dated by carbon dating, provided it has organic material which has not been contaminated since it was formed.
- Thermoluminescence can identify how long some things have been buried. The thermoluminescence clock is 'reset' when the objects are exposed to direct sunlight.
- Ice cores provide good evidence of past climates and temperatures. The cores preserve stable isotope ratios in water and gases, and solids like volcanic ash.
- Isotope dating works with many igneous rocks, and this can be used to determine absolute limits to the age range of fossils lying between two igneous layers.
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