The most common stalagmites arespeleothems, which usually form inlimestone caves.[4] Stalagmite formation occurs only under certainpH conditions within the cavern. They form throughdeposition ofcalcium carbonate and other minerals, which isprecipitated from mineralizedwater solutions. Limestone is the chief form of calcium carbonaterock, which isdissolved bywater that containscarbon dioxide, forming acalcium bicarbonate solution in caverns.[5] Thepartial pressure of carbon dioxide in the water must be greater than the partial pressure of carbon dioxide in the cave chamber for conventional stalagmite growth.[6]
Ifstalactites – the ceiling formations – grow long enough to connect with stalagmites on the floor, they form a column.
To preserve Stalagmites, it should normally not be touched, since the rock buildup is formed by minerals precipitating out of the water solution onto the existing surface;skin oils can alter thesurface tension where the mineral water clings or flows, thus affecting the growth of the formation. Oils and dirt (mud, clay) from human contact can also stain the formation and change its color permanently.
Another type of stalagmite is formed inlava tubes while molten and fluidlava is still active inside. Their mineralogical composition, close to that ofsiliceous minerals commonly found inbasalt (for example,obsidian), the main constituent ofvolcanic glass, is different. Their mechanism of formation/crystallization is also notably different from that of limestone stalagmites (CaCO 3) but the common point is that it remains driven by gravity. Drops of molten lava (siliceous material,SiO 2) solidify onto the floor of the already emptied lava tube, when the lava temperature sufficiently decreases after the passage and the complete purge of the main lava flow. Essentially, it is still the gravity deposition of material onto the floor of a cave (or a void).
However the difference from calcareous stalagmites is that the transport of siliceous material occurs in the molten state and not dissolved in aqueous solution; CO2 degassing does not play any significant role. With lava stalagmites, their formation also happens very quickly in only a matter of hours, days, or weeks, whereas limestone stalagmites may take up to thousands or hundred thousands of years. A key difference with lava stalagmites is that once the molten lava has ceased flowing, so too will the stalagmites cease to grow. This means that if the lava stalagmites were to be broken, they would never grow back.[2] Stalagmites in lava tubes are rarer than their stalactite counterparts because during their formation, the dripping molten material most often falls onto still-moving lava flow which absorbs or carries the material away.
The generic term "lavacicle" has been applied to lava stalactites and stalagmites indiscriminately, and evolved from the word "icicle".[2]
A common stalagmite foundseasonally or year round in many caves is the ice stalagmite, commonly referred to asicicles, especially in above-ground contexts.[7] Waterseepage from thesurface will penetrate into a cave and iftemperatures are belowfreezing temperature, the water will collect on the floor into stalagmites. Deposition may also occur directly from the freezing ofwater vapor.[8] Similar to lava stalagmites, ice stalagmites form very quickly within hours or days. Unlike lava stalagmites however, they may grow back as long as water and temperatures are suitable. Ice stalagmites are more common than their stalactite counterparts because warmer air rises to the ceilings of caves and may raise temperatures to above freezing.
Ice stalactites may also form corresponding stalagmites below them, and given time, may grow together to form an ice column.
Stalactites and stalagmites can also form onconcrete ceilings and floors, although they form much more rapidly there than in the natural cave environment.[9][10]
The secondary deposits derived from concrete are the result of concrete degradation, wherecalciumions are leached out of the concrete in solution and redeposited on the underside of a concrete structure to formstalactites and stalagmites.[10]Calcium carbonate deposition as a stalagmite occurs when the solution carries the calcium laden leachate solution to the ground under the concrete structure. Carbon dioxide is absorbed into thealkaline leachate solution,[11] which facilitates the chemical reactions to deposit calcium carbonate as a stalagmite.[12] These stalagmites rarely grow taller than a few centimetres.[13]
Secondary deposits, which create stalagmites, stalactites, flowstone etc., outside the naturalcave environment, are referred to as "calthemites".[10] These concrete derived secondary deposits cannot be referred to as "speleothems" due to the definition of the word.[9]
^C. Michael Hogan. 2010. “Calcium”. eds. A. Jorgensen, C. Cleveland.Encyclopedia of Earth. National Council for Science and the Environment.
^John), Fairchild, Ian J. (Ian (2012).Speleothem science: From process to past environments. Baker, Andy, 1968-. Oxford, U.K.: Wiley.ISBN9781444361094.OCLC782918758.{{cite book}}: CS1 maint: multiple names: authors list (link)
^abHill, C A, and Forti, P, (1997). Cave Minerals of the World, 2nd editions. pp. 217 & 225 [Huntsville, Alabama: National Speleological Society Inc.]
^abcSmith, G K. (2016). "Calcite straw stalactites growing from concrete structures". Cave and Karst Science, 43(1), 4–10.
^Macleod, G, Hall, A J and Fallick, A E, 1990. An applied mineralogical investigation of concrete degradation in a major concrete road bridge. Mineralogical Magazine, Vol.54, 637–644.
^Sundqvist, H. S., Baker, A. and Holmgren, K. (2005). "Luminescence in fast growing stalagmites from Uppsala, Sweden". Geografiska Annaler, 87 A (4): 539–548.
^Smith, G K., (2015). "Calcite Straw Stalactites Growing From Concrete Structures". Proceedings of the 30th 'Australian Speleological Federation' conference, Exmouth, Western Australia, edited by Moulds, T. pp. 93–108.
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