Last week I experienced an awkward but relatable moment in my archaeology class. “What’s the substance in the ground,” Professor Beisaw asked. The answer seemed obvious so I stated, “Dirt.” “That’s right. It’s soil! Most people would have incorrectly answered dirt,” she explained. “Oops,” I thought and immediately broke eye contact! I then thanked the heavens that I have a voice softer than a mouse and that Professor Beisaw heard a different student answered the question before me! She further explained that the soil around an artifact holds valuable information about the past, while dirt is simply the stain on a shirt. I have walked on this earth and felt the soil between my toes for over 19 years, and never once have I thought about the stories that soil might tell. I have even soiled its name by assuming that it was the same as dirt! I believe that people misunderstand archaeology because they disregard the importance of the artifact’s surroundings, specifically soil. I will attempt to illustrate soil’s importance through the use of stratigraphy.
First, the ground is composed of sloping or marginally horizontal layers or strata of different soil on top of each other. They can usually be distinguished by their color, texture, or composition. As Wendy Ashmore notes in her book, Discovering Our Past, this is called stratification. She further points out that the sequence of these layered deposits obeys the Law of Superposition, meaning the sequence of the strata reflects the order of deposits. Archaeological assessment of stratification is known as stratigraphy. The benefits of stratigraphy are astounding, but numerous people overlook them. Most notably, by recording and analyzing the artifact’s location in relation to other artifacts and strata, archaeologists can determine the function and age of the artifact.
This stratification example provides a wealth of information. Due to the law of superposition, the natural subsoil was deposited first. We can assume that the Iron Age ditch and post-hole were from the same occupation because they are in the same strata. The Iron Age soil was deposited next and then the Roman dump soil. The Roman wall was then built because it was placed deep into the soil, and next the Roman floor was built. After that are the remains of the Roman building. The medieval pit must have been built before the wall since the wall’s edge is slightly in the pit. These lines of analysis continue for the entire stratification. All this information allows archaeologist to determine the relative age of the artifacts and understand specific time periods.
The example also demonstrates the complexity of stratigraphy. Behavioral and transformative processes can disrupt strata. In a class exercise, students found between 10 to 15 strata and 9 to 16 features in the picture. These results were anything but conclusive. However, through careful examination and a well thought out research question, an archaeologist can distinguish the important aspects of the stratification. By attempting to understand the intricacies of this archaeological technique, individuals can come to understand the field as a whole.