Submitted by Sammy Smith (sammy@thesga.org)

Earthworms leave the soil (at least some species do) when there’s a lot of rain, because the soil can get so moist they begin to drown.

Archaeologists mostly deal with abandoned objects and places where people once lived or did other activities. After abandonment, these objects and locales are subject to various disturbances—from natural processes, from wild creatures, and from later human visitors—and even from dogs!

One post-abandonment disturbance we think about is the effect of earthworms. They burrow through the soil, producing micro-tunnels that can introduce organic matter and allow air and water to move through the soil more easily, and change the soil chemistry. Although these processes happen at a small scale relative to many archaeological features like foundations and fire pits, they still disturb the abandoned remains. Earthworm activity is an example of bioturbation, or natural processes by living things, including both plants and animals.

Researchers report that even soils that are not very hospitable to earthworms may host tens of thousands of them per acre. If an archaeological site has been abandoned for five centuries, how great an effect do you think earthworms have had on the site? What if the site has been abandoned five times that long?

Posted online on Friday, April 3rd, 2009