Before revision: upright=1.8|Schematic of an aquifer showing confined zones, groundwater travel times, a spring and a well An aquifer is an underground layer of water-bearing , permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt).
After revision: upright=1.8|Schematic of an aquifer showing confined zones, groundwater travel times, a spring and a well An aquifer is an underground layer of water-bearing material, consisting of permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt).