- Title
- Stalagmites and stalactites
- Creator
- Frisia, Silvia; Woodhead, Jon D.
- Relation
- Encyclopedia of Caves p. 1041-1048
- Publisher Link
- http://dx.doi.org/10.1016/B978-0-12-383832-2.00116-X
- Publisher
- Academic Press
- Resource Type
- book chapter
- Date
- 2019
- Description
- Stalactites and stalagmites are the most common type of cave secondary mineral deposits, collectively known as speleothems. Stalactites are centimeters to meters in scale, hang from the ceiling and grow toward the cave floor (Fig. 1). Stalagmites grow from the cave floor upward and are commonly fed by water dripping from an overhead stalactite (Fig. 2). Stalagmitic flowstones (Fig. 2) are a particular type of stalagmite formed by a thin flowing film of water itself fed by groups of dripping stalactites, and coat the cave floor and walls. When a stalagmite and the overhanging stalactite merge, they form a column (Fig. 3). Most stalactites and stalagmites are composed of low-magnesium calcite and, less frequently, aragonite, the rhombohedral and orthorhombic phases of calcium carbonate (CaCO3), respectively. Rare stalactites and stalagmites consisting of the Mg-carbonate huntite, halite (NaCl), gypsum (CaSO4 2H2O), opal (amorphous hydrated SiO2), and limonite (FeO(OH) nH2O) and even ice (H2O) have been found. To date, there is no evidence of stalactites or stalagmites entirely consisting of dolomite, a highly ordered double carbonate of calcium and magnesium CaMg(CO3)2. However, dolomite has been detected along with calcite, aragonite, and quartz in stalagmites and stalactites in Australian caves (Dhami et al., 2018). Stalactites and stalagmites likely started to develop in caves when the first carbonate rocks had been subaerially exposed and eroded that is well over 1 billion years ago. Most speleothems that have been extensively studied date from the Quaternary, and the genesis of these is commonly driven by the process of degassing, which occurs when drip waters having a high carbon dioxide concentration (pCO2) interact with the cave atmosphere that has a relatively low pCO2. It is, therefore, believed that occurrence of stalagmites and stalactites greatly increased since the rise of vascular plants in the Devonian, which led to an acceleration of chemical weathering, greater availability of soil CO2, and a decline in global atmospheric CO2 concentration. Chemical weathering of Ca-bearing silicate minerals by acidic waters generated in peat soil, for example, is very effective in yielding calcite stalactites and stalagmites in caves cut in to granite and gneiss; in such cases karst dissolution does not play a role in the genesis of these speleothems, but the presence of vascular plants does. The focus of the following sections is, therefore, on the genesis, structure, and chemical properties of calcium carbonate stalagmites and stalactites.
- Description
- 3rd
- Subject
- talactites; stalagmites; calcite; aragonite; climate change
- Identifier
- http://hdl.handle.net/1959.13/1460142
- Identifier
- uon:45868
- Identifier
- ISBN:9780128141243
- Language
- eng
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