Complex Engineering Found in Earthworks
Hopewell earthworks can have complicated designs, with many different shaped enclosures carefully situated in relation to each other and joined either by common walls or parallel passageways.
Not only was the design of the geometry complex. The building process was complicated as well. The embankment walls are not mere mounds of dirt piled into shapes. Each mound and wall is carefully constructed, with layers of different materials. The first stage was always to clear the topsoil and even some of the subsoil away, to create a flat sterile surface. Here, fires were burned before construction could begin. Also, fires were often burned on top of a layer before a layer of another material was applied.
Mounds and wall were often capped with a layer of gravel or red clay, implying that these earthworks may have been bare of vegetation or even decorated, rather than the green mounds we see today. There is some evidence that the entire surface of enclosures were stripped, sunken and unvegetated as well. This new vision of ancient earthworks makes the grand achievements of the Hopewell even more astounding in terms of the labor that must have been required.