The physical removal, transport, or redistribution of archaeological deposits, features, or artefacts by agents such as running water, wind, gravity (mass wasting) or ice, resulting in loss, truncation, or relocation of material and alteration of site morphology and context.

Principle

Erosion is a directional, selective process that truncates or exports parts of the archaeological record and re‑deposits some materials downslope or downstream, producing spatial displacement and preservation bias that depend on agent, energy and substrate.

Demonstration

Illustrative scenario — Situation: Heavy seasonal runoff on a river terrace erodes the terrace edge. Recognition: Stratigraphic sections show truncated deposits and artefacts in colluvial fans below. Action: Survey maps erosion scars and samples downstream deposits for secondary context analysis. Consequence: Original features are partially lost; downstream deposits are interpreted as reworked material rather than primary occupation layers.

Misapplication

Concluding that the absence of artefacts at a location implies absence of past human activity without considering that erosion may have removed evidence. The reasoning error is equating present absence with historical non‑existence rather than recognising post‑depositional loss.

Consequence

Unrecognised erosion causes underestimation of past activity, skewed density maps, truncated stratigraphic sequences and potential misdating; recognising erosion prompts targeted search for relocated deposits, use of geomorphological reconstruction and adjusted sampling.

Reversal

In very stable, cohesive substrates (bedrock, cemented gravels) or in settings without sufficient transport energy, erosion will not significantly remove deposits; in some contexts, erosion exposes buried features and thereby improves detectability even as it removes some material.

Boundary

Clearly within: Gully incision removing topsoil and archaeological layers and depositing redeposited material at the gully base. Boundary case: Sheetwash that subtly removes fine sediments over long periods producing widespread thinning rather than discrete removal. Clearly outside: In situ chemical diagenesis that alters materials chemically without physical export.

Semantic Tension

Landscape dynamics and preservation ↔ Interpretative certainty: geomorphic processes that shape landscapes are necessary to understand site formation but they create uncertainty about original extent and composition of archaeological deposits.

Synthesis

Erosion is both destructive and diagnostic: it can remove evidence and create secondary deposits whose recognition and geomorphological contextualisation are essential to reconstructing former site extent, chronology and activity patterns.