Stalactite
Encyclopedia
Speleothem
A speleothem , commonly known as a cave formation, is a secondary mineral deposit formed in a cave. Speleothems are typically formed in limestone or dolostone solutional caves.-Origin and composition:...
(secondary mineral) that hangs from the ceiling of limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
cave
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
s. It is a type of dripstone. The corresponding formation on the floor of the cave is known as a stalagmite
Stalagmite
A stalagmite is a type of speleothem that rises from the floor of a limestone cave due to the dripping of mineralized solutions and the deposition of calcium carbonate. This stalagmite formation occurs only under certain pH conditions within the underground cavern. The corresponding formation on...
.
Formation and type
Deposition (geology)
Deposition is the geological process by which material is added to a landform or land mass. Fluids such as wind and water, as well as sediment flowing via gravity, transport previously eroded sediment, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of...
of calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
and other minerals, which is precipitated from mineralized water solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
s. Limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
is the chief form of calcium carbonate rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...
which is dissolve
Dissolution (chemistry)
Dissolution is the process by which a solid, liquid or gas forms a solution in a solvent. In solids this can be explained as the breakdown of the crystal lattice into individual ions, atoms or molecules and their transport into the solvent. For liquids and gases, the molecules must be compatible...
d by water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
that contains carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, forming a calcium bicarbonate
Calcium bicarbonate
Calcium bicarbonate , also called calcium hydrogencarbonate, does not refer to a known solid compound; it exists only in aqueous solution containing the calcium , bicarbonate , and carbonate ions, together with dissolved carbon dioxide...
solution in underground caverns. The chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
for this reaction is:
-
- + + →
This solution travels through the rock until it reaches an edge and if this is on the roof of a cave
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
it will drip down. When the solution comes into contact with air the chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
that created it is reversed and particles of calcium carbonate are deposited. The reversed reaction is:
-
- → + +
An average growth rate is 0.13 millimetre (0.00511811023622047 in) a year. The quickest growing stalactites are those formed by fast-flowing water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
rich in calcium carbonate and carbon dioxide, these can grow at 3 millimetre (0.118110236220472 in) per year.
Every stalactite begins with a single mineral-laden drop of water. When the drop falls, it deposits the thinnest ring of calcite. Each subsequent drop that forms and falls deposits another calcite ring. Eventually, these rings form a very narrow (0.5 mm), hollow tube commonly known as a "soda straw
Soda straw
A soda straw is a speleothem in the form of a hollow mineral tube. They grow in places where water leaches slowly through cracks in rock, such as on the roofs of caves...
" stalactite. Soda straws can grow quite long, but are very fragile. If they become plugged by debris, water begins flowing over the outside, depositing more calcite and creating the more familiar cone-shaped stalactite. The same water drops that fall from the tip of a stalactite deposit more calcite on the floor below, eventually resulting in a rounded or cone-shaped stalagmite
Stalagmite
A stalagmite is a type of speleothem that rises from the floor of a limestone cave due to the dripping of mineralized solutions and the deposition of calcium carbonate. This stalagmite formation occurs only under certain pH conditions within the underground cavern. The corresponding formation on...
. Unlike stalactites, stalagmites never start out as hollow "soda straws." Given enough time, these formations can meet and fuse to create columns.
Stalactites can also form in lava tubes, although the mechanism of formation is very different.
Concrete
Stalactites can also form on concreteConcrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
, and on plumbing where there is a slow leak and limestone (or other minerals) in the water supply, although they form much more rapidly there than in the natural cave environment (description and experiments see literature).
The way stalactites form on concrete is due to different chemistry than those that form naturally in limestone caves and is the result of the presence of calcium oxide
Calcium oxide
Calcium oxide , commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature....
in concrete. This calcium oxide reacts with any rainwater that penetrates the concrete and forms a solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
of calcium hydroxide
Calcium hydroxide
Calcium hydroxide, traditionally called slaked lime, is an inorganic compound with the chemical formula Ca2. It is a colourless crystal or white powder and is obtained when calcium oxide is mixed, or "slaked" with water. It has many names including hydrated lime, builders lime, slack lime, cal, or...
. The chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
for this is:
-
- + →
Over time this calcium hydroxide solution reaches the edge of the concrete and, if the concrete is suspended in the air, for example, in a ceiling or a beam, then this will drip down from the edge. When this happens the solution comes into contact with air and another chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
takes place. The solution reacts with carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
in the air and precipitates calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
.
-
- + → +
When this solution drops down it leaves behind particles of calcium carbonate and over time these form into a stalactite. They are normally a few centimeters long and with a diameter
Diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
of approximately 5 millimetre (0.196850393700787 in).
Records
The White Chamber in the Jeita GrottoJeita Grotto
The Jeita Grotto In 1958, Lebanese speleologists discovered the upper galleries above the lower cave which have been accommodated with an access tunnel and a series of walkways to enable tourists safe access without disturbing the natural landscape. The upper galleries house the world's largest...
's upper cavern in Lebanon contains an 8.2 m (26.9 ft) stalactite which is accessible to visitors and is claimed to be the longest stalactite in the world. Another such claim is made for a 20 m (65.6 ft) stalactite that hangs in the Chamber of Rarities in the Gruta Rei do Mato
Gruta Rei do Mato
The Gruta Rei do Mato is a cave located near Sete Lagoas in Minas Gerais, Brazil, at the edge of the BR 040 highway, close to the off ramp to the city. From Sete Lagoas the cave can easily be reached by bus, taxi or car. Sete Lagoas is 70 kilometres from Belo Horizonte.The Gruta Rei do Mato has...
(Sete Lagoas
Sete Lagoas
Sete Lagoas is a city in the Brazilian state of Minas Gerais. The municipal area is 537 km² while the population was 217,506 in 2007.-Location:...
, Minas Gerais
Minas Gerais
Minas Gerais is one of the 26 states of Brazil, of which it is the second most populous, the third richest, and the fourth largest in area. Minas Gerais is the Brazilian state with the largest number of Presidents of Brazil, the current one, Dilma Rousseff, being one of them. The capital is the...
, Brazil). However, vertical cavers have often encountered longer stalactites while exploring. One of the longest stalactites viewable by the general public is in Doolin Cave, County Clare
County Clare
-History:There was a Neolithic civilisation in the Clare area — the name of the peoples is unknown, but the Prehistoric peoples left evidence behind in the form of ancient dolmen; single-chamber megalithic tombs, usually consisting of three or more upright stones...
, Ireland, in a karst
KARST
Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
region known as The Burren
The Burren
The Burren is a karst-landscape region or alvar in northwest County Clare, in Ireland. It is one of the largest karst landscapes in Europe. The region measures approximately 250 square kilometres and is enclosed roughly within the circle made by the villages Ballyvaughan, Kinvara, Tubber, Corofin,...
; what makes it more impressive is the fact that the stalactite is held on by a section of calcite less than 0.3 sqm.
Origin of the term
Stalactites are first mentioned (though not by name) by the RomanAncient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
natural historian Pliny
Pliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...
in a text which also mentions stalagmites and columns and refers to their creation by the dripping of water. The term "stalactite" was coined in the 17th century by the Danish Physician Ole Worm
Ole Worm
Ole Worm , who often went by the Latinized form of his name Olaus Wormius, was a Danish physician and antiquary.-Life:...
who created the word from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
root stalasso, (σταλάσσω), "to drip".
External links
- The Virtual Cave's page on stalactites
- "Stalactites" by Enrique Zeleny, Wolfram Demonstrations ProjectWolfram Demonstrations ProjectThe Wolfram Demonstrations Project is hosted by Wolfram Research, whose stated goal is to bring computational exploration to the widest possible audience. It consists of an organized, open-source collection of small interactive programs called Demonstrations, which are meant to visually and...
.