Growth patterns in tree rings are used in dendrochronology dating techniques.
Finding a fossil or artifact is exciting, but it raises many questions, not least of which is "How old is it?" Geologists, paleontologists, physicists and archaeologists have developed a host of techniques to determine just how old a particular object is, and often an accurate date can only be found by combining several approaches at once.
Instructions
1. Examine the location where the object was found for clues that would allow you to establish the date of the site. Often, if an object itself cannot be dated directly, the context in which it was found will give sufficient information to narrow down the age. If the site is buried or partially buried, there may be datable layers above or below the object. For example, a layer of volcanic ash lying above the object could indicate that the object is at least older than the eruption that produced that ash.
2. Look for other objects in the same site whose age may be more easily determined. Objects found together are likely to be of the same age, though not always. For example, imagine a college student finding a pair of socks next to an old newspaper in the layers of debris on the dorm room floor. The date on the newspaper is a clue as to how long the socks have been there. The same principle can apply to archaeological or paleontological sites: artifacts with inscriptions in a known language can provide clues, or a piece of charcoal or wood that can be dated by carbon-14 or tree ring examination might also narrow down the date.
3. Examine the object itself for distinctive characteristics indicating age. For artifacts, this can include styles and techniques of manufacture, as well as consideration of the materials: a stainless steel blade cannot date from before the invention of stainless steel, for example. For fossils of living creatures, identifying the species can be a big help, since other fossils of the same species may have been reliably dated by other means.
4. Test samples from the site and from the object by an appropriate radio isotope dating method, if possible. Not all objects or artifacts can be dated by these methods, and not all isotopes are applicable for all age ranges. Carbon 14 is very good for dating organic material up to about 50,000 years old but is useless when there is no carbon present, as in a stone arrowhead. However, a stone arrowhead could be dated by C-14 if it were found next to a firepit with charcoal in it. Layers of volcanic ash can sometimes be dated by different isotopes and other laboratory techniques, such as thermoluminescence.
Tags: have been, narrow down, object itself, stainless steel, stone arrowhead
