Earth as a History Book
Stratigraphy is the archaeologist's most fundamental tool: the principle that layers of soil, sand, and debris accumulate over time, with the oldest at the bottom and the newest at the top. Formalized by Nicolaus Steno in 1669 for geology and adapted for archaeology by Mortimer Wheeler and Kathleen Kenyon in the mid-20th century, stratigraphic excavation transformed archaeology from treasure hunting into a rigorous science of context.
The Law of Superposition
In an ideal world, each layer represents a distinct period of activity — a Roman floor, a medieval rubbish pit, a Victorian garden. Reality is messier: later digging cuts through earlier layers, worms and roots churn the soil, and erosion removes evidence entirely. This simulation lets you control disturbance and erosion to see how they degrade the stratigraphic record and create ambiguity in the archaeological timeline.
Recording the Section
Archaeologists document stratigraphy by drawing section profiles — precise scale drawings of trench walls showing each deposit's color, texture, thickness, and boundaries. These profiles, combined with plan drawings and photographs, form the permanent record of a site that is destroyed as it is excavated. The Harris Matrix, introduced in 1973, provides a formal diagram of stratigraphic relationships.
From Relative to Absolute Time
Stratigraphy alone tells you only which layers are older or younger. To pin the sequence to the calendar, archaeologists rely on datable materials within layers: radiocarbon samples, coins, pottery styles with known date ranges, or volcanic tephra from historically documented eruptions. The integration of relative and absolute dating transformed our understanding of human prehistory.