How Old Is It?
How do archaeologists know how old the site or artifact is that they find? Scientists developed different ways to date artifacts or features. These dating methods methods are very different ways to measure age and time.
One scientific method widely used by archaeologists to identify the age of an artifact is radiocarbon dating. Since all living things take in the element of carbon, the material must once have been part of something that lived in order for radiocarbon dating can be used. Radiocarbon dating can be used to date bone, wood, charcoal, clothing, wool, fur, shells, or antlers, but it can't be used to date on stone, metal, or pottery.
Radiocarbon dating reports how many years “before present” or BP or years ago. Radiocarbon dates tell us when something was alive, but not when the material was used. If we test a wooden tool, the radiocarbon dates tell us when the tree lived, not when people used the wood as a tool.
Stratigraphy involves studying the different layers of soils, rock or dirt at a site. It is doesn’t give an absolute date like radiocarbon dating. Each layer has its own color and texture. Lower layers are usually older than the ones above it. The top layers are usually the youngest or most recent. Archaeologists study layers to find out what is in them, including artifacts. For example, if you find a projectile point in a top layer and a scraper in a lower layer, the scraper is probably the older artifact.
Sometimes the stratigraphy of a site gets mixed up. An animal might dig a hole through it. A flood might wash some of it away or an earthquake might turn it upside down. Then understanding the stratigraphy becomes very difficult and more information or an excavation may be needed to figure it out.
Activity - Stratigraphy and Crossdating
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