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Also known as cap rock, seal rock

Caprock or cap rock is a hard, resistant, and impermeable layer of rock that overlies and protects a layer of softer material. In petroleum geology the softer lower layer may be a reservoir of oil or natural gas. The caprock acts similarly to the crust on a pie where the crust (caprock) prevents leakage of the soft filling (softer material). In landforms like mesas and buttes the caprock consists of sturdy erosion-resistant rock like granite or basalt that resists weathering more strongly than its supporting rock and results in differential erosion. It also influences hydrology by creating wat