Submitted by Sammy Smith (sammy@thesga.org)

Careful excavation and detailed note-taking are hallmarks of well-managed archaeological projects. This is because archaeology is a destructive science—any square centimeter of an archaelogical deposit can only be excavated once. There is no second chance.

Therefore, when archaeologists excavate, not only do they look for solid objects (for example, artifacts), they optimize the opportunity for noticing faint color and texture changes in the soil that signal something significant. Drip lines are an example of a kind of subtle evidence that a sharp eye can spot in the soil.

A drip line is made by falling water, usually rainwater. It looks like a series of little holes made by the action of drips repeated in one place. The little holes etch in the soil an echo of an edge up above, like the upper brow of a rock shelter or the margin of a roof that doesn’t have a rain gutter.

The photos record another kind of drip line, made by the slats of a hanging bench in an Atlanta park.

After the object that allows the drip line to form is gone, soil fills in the little holes the water made. The new soil may be a different color and texture. Therefore, when this part of the site is carefully excavated, the drip line can look like a line of dots. The archaeologist knows there was some kind of “edge” above the drip line.

Go find a drip line. Think about what valuable information it indicates about the object above it that made the drip line. Did a roof edge make the drip line? If this were an archaeological site, and you found this drip line, what would it tell you? What if you had information about other nearby features, like building foundations?

Posted online on Friday, March 20th, 2009