Dr. John Wah
The Science of Soil
Sterile Versus Cultural Soil
Stratigraphy is one of the many ways archaeologists make sense of what they are excavating. By examining the different strata, or layers, of the soil, archaeologists can begin to piece together a map of the archaeological site over time. Stratigraphy can be used to figure out which soil was associated with human occupation (and therefore likely to contain archaeological materials), but it can also illustrate certain events (like a fire) or natural disasters (like a flood). Stratigraphy is also a useful excavation guide as it can show archaeologists which layers are sterile (not associated with human occupation and not containing anything archaeological) and in which layers they should be keeping an eye out for cultural materials.
Cultural material accumulates where people live and work, leaving artifacts, organic matter (like compost), and other evidence of human activity to build up in the soil. Archaeologists can “see” human occupation layers in the ground, which are often distinct from sterile layers like subsoil, flood sediment, or bedrock. These soil layers provide vital clues about how sites were used, abandoned, and often reused over time.