Speleogenesis is the origin and development of
cave
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...
s, the primary process that determines essential features of the
hydrogeology
Hydrogeology (''hydro-'' meaning water, and ''-geology'' meaning the study of the Earth) is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust (commonly in aquif ...
of
karst
Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...
and guides its evolution. It often deals with the development of caves through
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
, caused by the presence of water with
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
dissolved within it, producing
carbonic acid which permits the
dissociation
Dissociation, in the wide sense of the word, is an act of disuniting or separating a complex object into parts. Dissociation may also refer to:
* Dissociation (chemistry), general process in which molecules or ionic compounds (complexes, or salts) ...
of the
calcium carbonate in the limestone.
Limestone
The majority of limestone caves are created by
calcium carbonate dissolution
Dissolution may refer to:
Arts and entertainment Books
* ''Dissolution'' (''Forgotten Realms'' novel), a 2002 fantasy novel by Richard Lee Byers
* ''Dissolution'' (Sansom novel), a 2003 historical novel by C. J. Sansom Music
* Dissolution, in mu ...
by the solvent action of
meteoric waters circulating through the rock.
In the presence of carbon dioxide saturated water, calcium carbonate reacts to form the soluble calcium bicarbonate.
CaCO
3 + CO
2 + H
2O → Ca(HCO
3)
2
As meteoric waters precipitate they dissolve atmospheric carbon dioxide to form a dilute carbonic acid solution, which builds up in permeable
fissures
A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes.
Ground fissure
A ...
,
bedding planes
In geology, a bed is a layer of sediment, sedimentary rock, or pyroclastic material "bounded above and below by more or less well-defined bedding surfaces".Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds., 2005. ''Glossary of Geology'' ...
, joints, and
faults within limestone rocks. The exposed limestone then reacts to become calcium bicarbonate which dissolves in the water and is removed from the fault as the solution flows away.
Phreatic
''Phreatic'' is a term used in hydrology to refer to aquifers, in speleology to refer to cave passages, and in volcanology to refer to a type of volcanic eruption.
Hydrology
The term phreatic (the word originates from the Greek , meaning "well" ...
passages develop in conditions of complete water-fill meaning that ceilings and walls may be eroded as readily as floors. The form is generally that of an ellipse along the host fissure, whilst more circular forms generally indicate faster solvent flow and deep pockets are often indicative of slower flow.
Vadose passages develop where the water has a free surface (i.e., in the vadose zone), and are varieties of entrenched, canyon-like channels as found with surface rivers. It is common to see a younger canyon entrenched in the floor of a phreatic passage, signifying a lowering of the
water table
The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated.
T ...
.
See also
*
Speleology
*
Phreatic
''Phreatic'' is a term used in hydrology to refer to aquifers, in speleology to refer to cave passages, and in volcanology to refer to a type of volcanic eruption.
Hydrology
The term phreatic (the word originates from the Greek , meaning "well" ...
References
External links
Exploring Earth: Observe an animation of cave formation an animation of cave formation in limestone deposits.
an interactive explanation of how rain, waves, lava, and bacteria can form caves.
Speleogenesis.com- a communication platform for physical speleology and karst science research.
Cave geology
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