Sedimentary strata accumulate layer upon layer over millions of years. Because younger sediment always buries older sediment, the principle of superposition lets geologists read a cliff face like a book: the deepest exposed layer is always the oldest. Each colored slab here represents a distinct depositional era, thicker slabs meaning either a longer time span or a faster accumulation rate.
Principle of superposition: age(layer i) < age(layer i+1) for i below i+1
thickness = deposition_rate × duration
layer_age(depth d) = Σ duration_i for all layers above depth d
- Excavation depth — scrubs a virtual trench downward through time, exposing progressively older strata.
- Erosion rate — speeds up or slows the crumbling/dust-particle animation as each layer face is cut back.
- Layer highlight — colors every slab by relative age instead of its natural rock-type color, making the time gradient obvious at a glance.
- Reset dig — restores the cliff to its undisturbed surface state.
Field geologists and geoheritage sites use exactly this superposition logic to date road cuts, canyon walls, and quarry faces without any lab equipment.