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A stalagmite (UK: /ˈstæləɡmt/ or US: /stəˈlæɡmt/; from the Greek σταλαγμίτης – stalagmitês, from σταλαγμίας – stalagmias, "dropping, trickling")[1] is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings. Stalagmites are typically composed of calcium carbonate, but may consist of lava, mud, peat, pitch, sand, sinter and amberat (crystallized urine of pack rats).[2][3]

The corresponding formation hanging down from the ceiling of a cave is a stalactite.

Formation and type

Limestone stalagmites

The most common stalagmites are speleothems, which usually form in limestone caves.[4] Stalagmite formation occurs only under certain pH conditions within the cavern. They form through deposition of calcium carbonate and other minerals, which is precipitated from mineralized water solutions. Limestone is the chief form of calcium carbonate rock, which is dissolved by water that contains carbon dioxide, forming a calcium bicarbonate solution in caverns.[5] The partial 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]

If stalactites – the ceiling formations – grow long enough to connect with stalagmites on the floor, they form a column.

Stalagmites 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 the surface tension where the mineral water clings or flows, thus affecting the growth of the formation. Oils and dirt from human contact can also stain the formation and change its color permanently.

Lava stalagmites

Another type of stalagmite is formed in lava tubes while lava is still active inside. The mechanism of formation is similar to that of limestone stalagmites. Essentially, it is still the deposition of material on the floors of caves; however with lava stalagmites, formation happens very quickly in only a matter of hours, days, or weeks, whereas limestone stalagmites may take up to thousands of years. A key difference with lava stalagmites is that once the lava has ceased flowing, so too will the stalagmites cease to grow. This means if the stalagmite were to be broken it would never grow back.[2] Stalagmites in lava tubes are rarer than their stalactite counterparts because during formation the dripping material falls onto still-moving lava floors that absorb or carry 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

A common stalagmite found seasonally or year round in many caves is the ice stalagmite, commonly referred to as icicles, especially in above-ground contexts.[7] Water seepage from the surface will penetrate into a cave and if temperatures are below freezing temperature, the water will collect on the floor into stalagmites. Deposition may also occur directly from the freezing of water 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

Another type of stalagmite is formed in lava tubes while lava is still active inside. The mechanism of formation is similar to that of limestone stalagmites. Essentially, it is still the deposition of material on the floors of caves; however with lava stalagmites, formation happens very quickly in only a matter of hours, days, or weeks, whereas limestone stalagmites may take up to thousands of years. A key difference with lava stalagmites is that once the lava has ceased flowing, so too will the stalagmites cease to grow. This means if the stalagmite were to be broken it would never grow back.[2] Stalagmites in lava tubes are rarer than their stalactite counterparts because during formation the dripping material falls onto still-moving lava floors that absorb or carry 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

  1. ^ σταλαγμίας, Henry George Lidde