Artifacts are dated through specific archaeological techniques.
Dating is one of the fundamental practices in archaeology. By developing a database of readings of various areas, archaeologists can cross-identify patterns in the makeup of soil and other materials. By comparing tree growth patterns, natural disasters or artifacts, archaeologists can more accurately determine the order, and approximate date, of materials.
Superposition
The Law of Superposition identifies that younger strata, or layers, are deposited above older strata. This is only possible during normal conditions. For example, an earthquake could disturb the strata by depositing older material on top of the younger material. Another possibility is the deposition of soot over rock during high rainfall. Superposition is particularly useful when studying soil layers. This line of study is the most fundamental ways for archaeologists to study the relative ages of materials.
Cross-Dating
Cross-dating uses the consistencies in the superposition analysis to compare the time composition of various surfaces in the ground. For example, samples are taken from sites five miles apart. Each sample contains a layer of lava. With the use of cross-dating, archeologists can line up samples from different sites to determine the order of events. This method can be used, for example, to assess whether the lava from a volcano reached a certain point.
Radiocarbon Dating
Radiocarbon, also called Carbon-14, dating is a widely used and well-known dating method of organisms. Developed in 1949, the method added a valuable tool for archaeologists. The method measures the amount of C-14 that has decayed on the sample. Scientists have identified the decay rate and can therefore determine approximately how much time has passed since the organism died. The method does have its drawbacks: for example, the size of the sample needs to be large enough to go through a purification and distillation process. This removes some of the matter, including C-14.
Dendrochronology
Also referred to as tree-ring dating, dendrochronology helps give a relatively accurate read of the date. Rings found in areas with similar weather conditions can be compared. The rings tell the archeologist the variations in rainfall and seasons. The same species of tree are the only ones that can be compared for full accuracy. However, a relatively accurate read can be attained from different species of trees by analyzing the distance between rings; this is due to rainfall trends. Not all trees have distinctive seasonal patterns.
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