| A | B |
|---|
| infiltration | the process by which precipitation that falls on land enters the ground |
| porosity | the percentage of pore space in a material |
| zone of saturation | the depth below Earth's surface at which groundwater completly fills all the pores of a material |
| water table | the upper boundary of the zone of saturation |
| permeability | the ability of a material to let water pass through it |
| aquifer | where most groundwater flows through permeable layers |
| cave | a natural underground opening with a connenction to Earth's surface |
| sinkhole | a depression in the ground caused by the collapse of a cave or by the direct dissolution of bedrock by acidic rain or moist soil |
| karst topography | limestone regions that have sinkholes, sinks, and sinking streams |
| stalactite | cone-shaped or cylindrical structures that hang from a cave's ceilings like isicles |
| stalagmite | mound-shaped dripstone deposits underneath the stalactites |
| travertine | another type of dripstone formation that are composed of another type of limestone |
| spring | natural discharge of groundwater |
| hot spring | a spring that discharges water that is much warmer than the average annual temperature |
| geyser | explosive hot springs that erupt at regular intervals |
| well | holes that are dug or drilled deep into the ground to reach a reservoir of groundwater |
| drawdown | teh difference between the original water-table level and the water level in the pumped well |
| recharge | the water from precipitation and runoff that is added back to the zone of precipitation |
| artesian well | a spring that discharges pressurized water |
