Aquiclude

Part of speech: noun

Definitions

1. A layer of rock or sediment that does not allow water to pass through, preventing groundwater from moving between aquifers
2. A geological formation acting as a barrier to the flow of water, thereby isolating aquifers from one another
3. An underground stratum that is essentially impermeable, stopping water migration and separating water-bearing layers

Etymology: "Aquiclude" is a technical coinage built from two parts: "aqui-", a combining form from "aquifer" (itself from Latin "aqua," water, plus "-fer," bearing), and the Latin verb "claudere," meaning "to shut." Put together, the name describes exactly what the rock does: it shuts water in or out. Geologists needed a term for impermeable layers that sit above, below, or between water-bearing strata, and this word supplies it. The pairing is a useful mirror image. An aquifer is a rock that lets water pass through and be stored; an aquiclude is its opposite, a layer dense or tight enough to stop that movement. Where the two sit together, the aquiclude can keep neighboring aquifers hydraulically separate, so that water in one does not drain into another.