Underground lake
An underground lake is a body of standing water beneath Earth’s surface, usually occupying a cave or another natural subterranean cavity.
Phreatic zone: The subsurface region where pores and fractures are saturated with groundwater. Many cave lakes occupy cavities below the water table, within this saturated zone.
Dragon's Breath Cave: A Namibian cave containing one of the world’s largest known non-subglacial underground lakes. Its vast lake illustrates how a single subterranean cavity can hold immense water.
Groundwater: Water stored beneath Earth’s surface in soil, sediment, and rock formations. Underground lakes are a visible, open-cavity form of subsurface water.
Subterranean fauna: Animals adapted to living underground, including species specialized for caves and groundwater. Underground lakes may contain poorly known organisms isolated from surface habitats.
Water table: The upper surface of groundwater, where subsurface pressure equals atmospheric pressure. Its elevation often sets the level of water in connected cave passages.
Cenote: A water-filled natural sinkhole, especially one formed in limestone terrain. Cenotes expose groundwater at the surface while often connecting to submerged cave systems.
Speleology: The scientific study and exploration of caves and related subterranean features. Speleologists map cave lakes and investigate their geology and hydrology.
Cave mapping: The surveying and representation of cave passages, chambers, and features. Flooded or inaccessible spaces make the full extent of lake systems difficult to map.
Karst: Landscape formed as soluble rock dissolves, producing features such as caves, sinkholes, and underground drainage. Karst terrain commonly creates the cavities and conduits that hold underground lakes.
Lake Vostok: A large subglacial lake beneath Antarctica’s ice sheet, sealed from the atmosphere for millions of years. It is an underground lake beneath ice rather than one housed in a cave.