Astalagmite(UK:/ˈstæləɡˌmaɪt/,US:/stəˈlæɡmaɪt/;fromGreekσταλαγμίτης(stalagmítēs);fromAncient Greekσταλαγμίας(stalagmías)'dropping, trickling' and-ίτης(-ítēs)'one connected to, a member of')[1] is a type of rock formation that rises from thefloorof acavedue to the accumulation of materialdepositedon the floor fromceilingdrippings. Stalagmites are typically composed ofcalcium carbonate,but may consist oflava,mud,peat,pitch,sand,sinter,and amberat (crystallized urine ofpack rats).[2][3]
The corresponding formation hanging down from the ceiling of a cave is astalactite.
Formation and type
editLimestone stalagmites
editThe most common stalagmites arespeleothems,which usually form inlimestonecaves.[4]Stalagmite formation occurs only under certainpHconditions within the cavern. They form throughdepositionofcalcium carbonateand other minerals, which isprecipitatedfrom mineralizedwater solutions.Limestone is the chief form of calcium carbonaterock,which isdissolvedbywaterthat containscarbon dioxide,forming acalcium bicarbonatesolution in caverns.[5]Thepartial pressureof 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 oilscan alter thesurface tensionwhere 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.
Lava stalagmites
editAnother type of stalagmite is formed inlava tubeswhile molten and fluidlavais still active inside. Their mineralogical composition, close to that ofsiliceousminerals 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; CO2degassing 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]
Ice stalagmites
editA common stalagmite foundseasonallyor year round in many caves is the ice stalagmite, commonly referred to asicicles,especially in above-ground contexts.[7]Waterseepagefrom thesurfacewill penetrate into a cave and iftemperaturesare belowfreezingtemperature, 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.
Concrete derived stalagmites
edit
Stalactites and stalagmites can also form onconcreteceilings 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, wherecalciumionsare leached out of the concrete in solution and redeposited on the underside of a concrete structure to formstalactitesand stalagmites.[10]Calcium carbonatedeposition 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 thealkalineleachate 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 naturalcaveenvironment, 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]
Records
editThe largest known stalagmite in the world exceeds 70 metres (230 ft) in height and is inSơn Đoòng Cave,Vietnam.[14]
In theZagros Mountainsof south Iran, approximately 6 km (3.7 miles) from the ancient city ofBishapur,in theShapur caveon the fourth of five terraces stands the 3rd-centurycolossal statue of Shapur I,second ruler of theSassanid Empire.The statue, carved from one stalagmite, is nearly 7 m (23 ft) high.[citation needed]
Photo gallery
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Coves d’Artà,Mallorca, Spain -
Seven-star Cave,Guilin, China -
A “crayfish back”,Jenolan Caves,New South Wales, Australia -
Hérault,France -
Castellana Grotte,Apulia, Italy
References
edit- ^σταλαγμίας,Henry George Liddell, Robert Scott,A Greek-English Lexicon,on Perseus.
- ^abc Larson, Charles (1993).An Illustrated Glossary of Lava Tube Features, Bulletin 87, Western Speleological Survey.p. 56.
- ^Hicks, Forrest L. (1950)."Formation and mineralogy of stalactites and stalagmites"(PDF).12:63–72.Retrieved2013-07-08.
{{cite journal}}:Cite journal requires|journal=(help) - ^"How Caves Form".Nova.PBS.Retrieved2013-07-01.
- ^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) - ^Keiffer, Susan (2010)."Ice stalactite dynamics".Retrieved2013-07-08.
- ^Lacelle, Denis (2009)."Formation of seasonal ice bodies and associated cryogenic carbonates in Caverne de l'Ours, Québec, Canada: Kinetic isotope effects and pseudo-biogenic crystal structures"(PDF).Journal of Cave and Karst Studies. pp. 48–62.Retrieved2013-07-08.
- ^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.
- ^"Son Doong Cave (Hang Sơn Đoòng)".Wondermondo. 15 June 2014.
External links
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