The area that we are working in today has a roasting pit that the Mogollon people used for cooking. We are finding charcoal left behind by their cooking fires. Karl tells us that charcoal is an "archaeologist's delight." Charcoal is another artifact that helps archaeologists tell how old a site is.
When a large amount of charcoal is found, it is collected to do a "flotation sample." This sounds pretty scientific, but the process is really very simple. The fill from the roasting pit, which includes lots of charcoal, is put in water. The charcoal floats to the top and is skimmed off, dried, and sent to a lab. At the lab, a botanist can analyze it and tell what kinds of plant material are present. This charcoal also provides information about the environment that the prehistoric people lived in.
The archaeologist then decides what kind of plant charcoal to send to a lab for radiocarbon dating. Radiocarbon dating tells you the date when something died, so archaeologists want to carefully choose what type of material to date. For instance, a tree could have been used to build a pithouse or a pueblo long after the tree died. The radiocarbon date would not be accurate in determining when that site was built. But if the material you are dating is corn, for example, you know that it was used within a few years of when it died. This helps to give the archaeologist a pretty reliable estimate of when people used a particular site. So, when we find charcoal, we get excited!
Credits: Courtesy of Shayne Russell