unconfined aquifer An aquifer characterized by the absence of an aquitard above it, so that thewater table forms the upper boundary of the aquifer and is free to move with atmospheric influences such as atmospheric pressure
An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, orsilt) from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude (or aquifuge), which is a solid, impermeable area underlying or overlying an aquifer. If the impermeable area overlies the aquifer pressure could cause it to become a confined aquifer.