Speleogenesis

Speleogenesis is the geological process by which caves are formed in soluble rocks, most commonly carbonate rocks such as limestone and dolostone, but also gypsum and, in some cases, evaporites. It encompasses the development of cave conduits through dissolution and related chemical weathering driven by groundwater flow. The term contrasts with karstification as a landscape-scale process, though the two are closely related.

Most commonly, caves develop as meteoric water rich in carbon dioxide percolates into the subsurface and dissolves limestone or related rocks. In the phreatic stage, water fills voids and conduits, dissolving and enlarging networked passages with rounded cross sections. In the vadose stage, falling or dripping water enlarges channels and forms fractures and narrow tubes with cup-shaped scallops along the walls, creating tunnel-like features.

Dissolution is aided by carbonic acid formed when CO2 dissolves in water; under some conditions sulfuric acid or other acids produced by microbial activity can also drive speleogenesis, creating features distinct from carbonated dissolution. Hypogene speleogenesis refers to cave formation driven by rising groundwater from depth, chemically weathering rocks with acids not related to surface rainfall; this can produce maze-like patterns and polyhedral rooms.

The lithology of the host rock controls cave development: soluble rocks such as limestone, dolostone, and gypsum respond readily to water; structural features like joints, faults, and permeability pathways guide where conduits form. Caves develop within aquifers or in recharge zones and often leave behind characteristic deposits called speleothems after drainage.

Timescales range from tens of thousands to millions of years, depending on rock type, climate, and hydrology. Speleogenesis integrates hydrology, geology, and geochemistry to explain the diversity of cave forms worldwide.