Earth

Where do caves form?

A large number of factors influence the formation of cave systems : chemical factors and climate control the dissolving capacity of water; geological factors control the type of rock, the geological structure and the characteristics of fracturing and jointing, which in their turn control underground water circulation and the development and trend of the cave zone; topographic factors such as altitudes gradient and the presence of deep valleys control the prevalently vertical or horizontal development of karst systems.
Caves therefore show different characteristics depending on the conditions and the environment in which they were formed.
Tropical caves
In tropical environments, all caves have similar characteristics. They are often arranged in vast underground systems, generally with a prevalently horizontal development, often drained by veritable underground rivers, and cave passages are very large and rich with speleothemes. Thanks to high temperatures, dissolution reaction is fast: since water filtering underground is very aggressive due to the presence of CO₂ and organic acids deriving from the dense plant overgrowth, it rapidly dissolves large quantities of limestone near the surface, soon becoming saturated or oversaturated, thus forming large quantities of speleothemes, which are a peculiar features of tropical karst.
High mountain caves
On the extreme opposite hand, caves in high mountain areas have a prevalently vertical trend due to the energetic potential created because of the large differences in altitudes and a geological structure that is generally complex, with big shafts, which are often very deep (at times over 600 m). Due to the slower dissolution speed as a result of low temperatures, circulating water may remain aggressive even at deeper levels, thus creating deep and vertical systems. Because of low temperatures, speleothemes are on the contrary very rare. On the surface, vertical shafts and sinkholes are often peculiar features. Their formation is often due to the conjoined action of karst processes and corrosion processes controlled by the presence of ice and snow.