Cave formations are produced when calcium carbonate saturated - GLG - 101 View Full Document These long, slender stalactites are called “soda straws”. They are hollow and can be 20 or more feet long. Kartchner Caverns in southern Arizona has excellent examples of these formations. (*) This is called cave drapery. The individual segments resemble bacon and is called “cave bacon”. (*) And if you are really hungry… eggs. This is another bacon formation. If you are hungry enough it probably does look like bacon. (*) The “egg” is the beginning of a stalagmite. (*) This preview has intentionally blurred sections. Sign up to view the full version. View Full Document Sinkholes and Karst Topography Sinkholes and Karst Topography MONTEZUMA’S WELL NEAR CAMP VERDE, ARIZONA MONTEZUMA’S WELL NEAR CAMP VERDE, ARIZONA Limestone is easily dissolved by acidic groundwater. Extensive caverns like Carlsbad or Mammoth Cave in Kentucky are obvious examples. Sinkholes are also created by limestone solution.

(*) Sinkholes and Karst Topography Sinkholes and Karst Topography These are both examples of sinkholes in Arizona. The image above is along the Little Colorado River (entrenched meanders). The one on the right is Montezuma’s Well. Both are the result of limestone solution to produce a cavern, and then the roof of the cavern collapsing to produce the sinkhole. (*) This preview has intentionally blurred sections. Sign up to view the full version. View Full Document Sinkholes and Karst Sinkholes and Karst Topography Topography Perhaps the most famous sinkhole in recent U.S. history is the one formed in May 1981, in Winter Park, Florida near Orlando. The sinkhole is roughly circular but elongated, (approximately 300 feet by 300 feet in size). It swallowed one house and shed, half of the municipal swimming pool, a Porsche sports car, several large oak trees, a section of the crossing street and adjoining street and an estimated 4 million cubic feet of soil. The sinkhole also damaged three other Porsche sports cars and a pick- up camper that slid into the crater. (*) Disappearing Lake These are a couple of interesting sinkhole links.

Sinkholes and Karst Topography Sinkholes and Karst Topography Figure 17.27 Acidic groundwater dissolves limestone easily. This produces caverns. As the caverns grow in size the roof becomes unstable and collapse to produce a sinkhole. As sinkholes grow in size and number a pockmarked landscape develops called Karst Topography. (*) This preview has intentionally blurred sections. Sign up to view the full version. View Full Document Sinkholes and Karst Topography Sinkholes and Karst Topography Water Table Unsaturated Zone Zone of Saturation The formation of a sinkhole begins at the water table. Water Soluble Rock Groundwater containing carbonic acid begins to dissolve the soluble rock – which in most cases is limestone. (*) Sinkholes and Karst Topography Sinkholes and Karst Topography Water Table Unsaturated Zone Zone of Saturation With fluctuations of the water table over time the cavities become larger. (*) This preview has intentionally blurred sections. Sign up to view the full version. Geology of Caves Geology of Caves W. E. Davies and I. M. Morgan US Geological Survey What is a cave?

A cave is a natural opening in the ground extending beyond the zone of light and large enough to permit the entry of man. Occurring in a wide variety of rock types and caused by widely differing geological processes, caves range in size from single small rooms to interconnecting passages many miles long. The scientific study of caves is called speleology (from the Greek words spelaion for cave and logos for study). It is a composite science based on geology, hydrology, biology, and archaeology, and thus holds special interest for earth scientists of the U.S. Geological Survey. Caves have been natural attractions since prehistoric times. Prolific evidence of early mans interest has been discovered in caves scattered throughout the world. Fragments of skeletons of some of the earliest manlike creatures (Australopithecines) have been discovered in cave deposits in South Africa, and the first evidence of primitive Neanderthal Man was found in a cave in the Neander Valley of Germany. Cro-Magnon Man created his remarkable murals on the walls of caves in southern France and northern Spain where he took refuge more than 1O,000 years ago during the chill of the ice age. Interest in caves has not dwindled.

Although firm figures for cave visitors are not available, in 1974 about 1.5 million people toured Mammoth Cave in Kentucky, and more than 67O,000 visited Carlsbad Caverns in New Mexico, two of the most famous caves in the United States. Types of Caves A simple classification of caves includes four main types and several other relatively less important types. Solution caves are formed in carbonate and sulfate rocks such as limestone , dolomite , marble , and gypsum by the action of slowly moving ground water that dissolves the rock to form tunnels, irregular passages, and even large caverns along joints and bedding planes. Most of the caves in the world-as well as the largest-are of this type. lava caves are tunnels or tubes in lava formed when the outer surface of a lava flow cools and hardens while the molten lava within continues to flow and eventually drains out through the newly formed tube. Sea caves are formed by the constant action of waves which attacks the weaker portions of rocks lining the shores of oceans and large lakes. Such caves testify to the enormous pressures exerted by waves and to the corrosive power of wave-carried sand and gravel.

glacier caves are formed by melt water which excavates drainage tunnels through the ice. Of entirely different origin and not to be included in the category of glacier caves are so-called "ice caves," which usually are either solution caves or lava caves within which ice forms and persists through all or most of the year. In desert areas, some shallow caves may be formed by the sandblasting effect of silt or fine sand being blown against a rock face. These eolian caves, some of which are spectacular in size, are surpassed in number by caves of other origins in most deserts. More common even in the driest deserts are sandstone caves eroded in part by water, particularly if the sandstone is limy. Caves commonly known as "wind caves," such as the one in Wind Cave National Park in South Dakota, are named not for the mode of origin of the cave but for the strong air currents that alternately blow in or out of the cave as the atmospheric pressure changes. Most wind caves are, in fact, solution caves. How Caves Form The melt-water streams draining out along the floor of a glacier cave or the surging, pounding waves at the mouth of a sea cave offer immediate evidence of the origin of these caves.

Solution caves, however, have always been a source of wonder to man. How do these extensive, complex, and in some places beautifully decorated passageways develop? Solution caves are formed in limestone and similar rocks by the action of water; they can be thought of as part of a huge subterranean plumbing system. After a rain, water seeps into cracks and pores of soil and rock and percolates beneath the land surface. Eventually some of the water reaches a zone where all the cracks and pores in the rock are already filled with water. The term water table refers to the upper surface of this saturated zone. calcite (calcium carbonate ), the main mineral of limestone , is barely soluble in pure water. Rainwater, however, absorbs some carbon dioxide as it passes through the atmosphere and even more as it drains through soil and decaying vegetation. The water, combining chemically with the carbon dioxide, forms a weak carbonic acid solution. This acid slowly dissolves calcite , forms solution cavities, and excavates passageways. The resulting calcium bi carbonate solution is carried off in the underground drainage system.

It was once believed that caves formed near the Earths surface-above the saturated zone-where the water moved downward through the cracks and pore spaces. This view, however, left many cave features unexplained. Why, for instance, are cave passages nearly horizontal, in places crossing folded or tilted rock structures? How would horizontal passages form at several different but persistent levels? Recent studies of the movement and chemistry of ground water have shown that the first stage in cave development-the dissolving of carbonate rocks and the formation of cavities and passage-ways-takes place principally just below the water table in the zone of saturation where continuous mass movement of water occurs. A second stage in cave development occurs after a lowering of the water table (the water table normally sinks as the river valleys deepen). During this stage, the solution cavities are stranded in the unsaturated zone where air can enter. This leads to the deposition of calcite , which forms a wide variety of dripstone features. The chemical process causing deposition of calcite is the reverse of the process of solution. Water in the unsaturated zone, which dissolved some calcite as it trickled down through the limestone above the cave, is still enriched with carbon dioxide when it reaches the ventilated cave.

The carbon dioxide gas escapes from the water (just as it escapes from an opened bottle of soda pop). The acidity of the water is thereby reduced, the calcium bi carbonate cannot remain in solution, and calcite is deposited as dripstone. Cave Features The decorative dripstone features are called speleothem s (from the Greek spelaion for cave and theme for deposit). When these structures are highlighted by lanterns or electric lights, they transform a cave into a natural wonderland. The most familiar speleothem s are stalactite s and stalagmite s. stalactite s hang downward from the ceiling and are formed as drop after drop of water slowly trickles through cracks in the cave roof. As each drop of water hangs from the ceiling, it loses carbon dioxide and deposits a film of calcite . Successive drops add ring below ring, the water dripping through the hollow center of the rings, until a pendant cylinder forms. Tubular or "soda straw" stalactite s grow in this way; most are fragile and have the diameter of a drop of water, but some reach a length of perhaps a yard or more.

The large cone-shaped stalactite s begin as these fragile tubes and then enlarge to cones when enough water accumulates to flow along the outside of the soda straws. Deposition of calcite on the outside of the tubes, most of which are near the ceiling and taper downward, results in the familiar cone shapes. Stalagmites grow upward from the floor of the cave generally as a result of water dripping from overhanging stalactite s. A column forms when a stalactite and a stalagmite grow until they join. A curtain or drapery begins to form on an inclined ceiling when the drops of water trickle along a slope. Gradually a thin sheet of calcite grows downward from the ceiling and hangs in decorative folds like a drape. Sheets of calcite that are deposited on the walls or floor by flowing water are called flowstone. Rimstone dams are raised fence-like deposits of calcite on the cave floor that form around pools of water. Helictites are curious twisted or spiraling cylinders or needles. They apparently develop when water seeps through the ceiling so slowly that slight chemical or physical changes can cause reorientation of the crystal structure of the calcite or gypsum.

Cave corals, also formed by slowly seeping water, are small clusters of individual knobs. Most cave passages contain deposits of material that have been washed into the cave. This material, known as cave fill, varies from sand and clay to stratified gravel. The pebbles in these deposits often are highly polished or frosted and sometimes are as large as 6 inches in diameter. Cave fills are particularly noteworthy because they contain materials that reflect a geologic history and a record of past climates of the surrounding area. Rock material produced by the collapse of the ceiling or walls of a cave is called breakdown and may range in size from plates and chips to massive blocks. Most breakdown present in caves today appears to have occurred thousands of years ago. It is generally associated with the early history of cave development. The size and depth of many caves in the United States are impressive. Seven caves have more than 15 passage miles. The longest is the Flint-Mammoth Cave system in Kentucky with more than 169 miles.

The other six are Jewel Cave in South Dakota (54.4 miles), Organ Cave in West Virginia (32 miles), Wind Cave in South Dakota (28.7 miles), Cumberland Caverns in Tennessee (23.2 miles), Sloan Valley Cave system in Kentucky (22.4 miles), and Crevice Cave in Missouri (20.8 miles). The deepest cave in the United States is Neff Canyon in Utah. There, a depth of 1,189 feet below the entrance is reached along a steeply sloping 1,700-foot passage. The second deepest cave is Carlsbad Caverns in New Mexico; its lowest point is 1,022 feet below the entrance. Ellisons Cave system in Georgia, a close rival of Carlsbad, has a depth of nearly 1,000 feet. The largest cave room is in Carlsbad Caverns, where the Big Room covers 14 acres. This room is 1,800 feet long and ranges up to 1,100 feet wide. The maximum height of the ceiling is 225 feet.

The size of the Big Room, the length of the caverns (14.9 miles, the 11th longest in the United States), and the depth probably make Carlsbad the biggest cave in the United States. Minerals Found in Caves Many interesting minerals are found in caves in addition to the calcite which forms the major features. Aragonite, a calcium carbonate mineral similar to calcite but not as common, often occurs in intricate needles known as anthodites. Gypsum (calcium sulfate) and related calcium sulfate minerals are next to calcite in abundance. Some caves, although they are developed in limestone , have extensive passages lined with fine, curling growths of gypsum flowers. In other caves, selenite (a less common variety of gypsum) forms long transparent rods or nests of fibrous crystals. Sulfates of sodium and magnesium are also found in caves, although they are less conspicuous than gypsum. Iron minerals in the form of oxides (limonite) and hydroxide (goethite) occur in caves and in some places form stalactite s. Manganese minerals in caves are commonly present as thin, sooty coatings on walls and ceilings and in earth fills.

Nitro calcite (calcium nitrate) is abundant in earth fills in many caves, but individual fragments are generally microscopic. Barite (barium sulfate) and celestite (strontium sulfate) also occur in earth fills. In some solution caves, clay minerals exist in relatively pure forms; these include the less common varieties attapulgite and endellite. In deep caves encountered during mining operations, a number of ore minerals have been found in the decorative wall draperies. Most common are azurite and malachite (forms of copper carbonate ). About 50 other minerals also have been reported in cave deposits. Uses of Caves Studies are underway in Europe to extend the use of caves for domestic cold storage, air conditioning, and water supply purposes. A large cave in southwestern Virginia is used as a natural tunnel by the Southern Railway. From the early 19th century through the Civil War, caves in Kentucky, Tennessee, Virginia, West Virginia, Alabama, Georgia, Arkansas, and Missouri were important sources of nitrates, an essential ingredient of gun powder. Surface or near-surface accumulations of nitrate salts form coatings on rock walls, fill cracks and crevices, and mingle with cave earth.

The origin of the nitrate salts is not clearly understood, but the salts are believed to result from the action of nitrifying bacteria on organic matter or humus. Although no accurate records of production were kept, it has been estimated that over 15,000 tons of niter earth (producing 200 tons of potassium nitrate) were removed from Mammoth Cave in Kentucky between 1811 and 1814. Caves have also been a source of bat guano, a material mined as a phosphate fertilizer in the Southern United States and Mexico. In general, the largest deposits have occurred in limestone caves within the flight range of the Mexican free-tailed bat. Geological Survey Investigations Scientists value caves as natural underground laboratories. Of paramount importance is the fact that caves and other solution cavities in limestone have a direct bearing on the under ground water system. Cavernous limestone strata are among the most productive aquifers (water-bearing beds) in the United States and are therefore important sources of water. Because of this, U.S. Geological Survey research programs concerned with limestone regions commonly include studies of the path, rate of flow, amount, and quality of water circulating through caves and hidden passageways.

Geological engineers and others concerned with ground stability are aware that regions underlain by cavernous limestone present special construction problems. Studies of the subsurface conditions are especially important in areas of limestone and gypsum because of the danger of ground failure and subsidence. Exploring Caves There are about 17,000 known caves in the United States. They occur in every State except Rhode Island and Louisiana. About 125 caves have been opened to the public for study and enjoyment. Of these, 15 are in national parks or monuments, and 30 are in State parks. The remainder are privately owned and operated. Most of these caves are in the Appalachian Mountains, the Ozark Mountains, the Black Hills, and the limestone regions of Kentucky, Tennessee, and Indiana. Caution! Exploring newly discovered or unattended caves can be extremely dangerous! Through experience, a set of safety rules has evolved that-if observed-may prevent accidents. If you plan to go cave exploring: Always tell someone where you are going and when you can be expected to return; obtain permission from the owner of the cave for the visit. Respect gates, whether they are in the field or at the cave entrance. Never enter a cave alone.

Always carry several sources of light; do not depend solely on flashlights. Make sure you have proper equipment in good working condition. Never go beyond your physical and technical capabilities. For the sake of conservation, keep visits to a minimum. Better yet, meet with knowledgeable and experienced cavers. Association with a group of experienced spelunkers is the best safety insurance that you can have. Caves are natural features and should be protected, but many have been vandalized by careless visitors or damaged by poorly planned commercial development. Some caves have been stripped of speleothem s which took thousands of years to form and in many places will not form again. All should try to prevent this random destruction of these natural wonderlands. Follow the footprints of others; look but don't touch; bring away only photographs; leave no evidence of your visit. Geology Cave Brochure Geology of the Cave The story of the geologic formation of the Cave of the Mounds begins with the creation of the rock in which the Cave is found. The Cave was formed within sedimentary rock, a limestone made of compacted seashells. This rock dates back over 400 million years to the Ordovician Period of the earth’s geologic history.

During this Ordovician Period, warm shallow seas covered the continent where we find Wisconsin today. Abundant shell life could thrive in these seas. Layers and layers of calcium carbonate shell debris accumulated and slowly hardened into limestone. Thousands of feet of limestone and other sedimentary rocks were laid down during this Ordovician Period. Millions of years ago, the seas receded leaving these layers of rock behind. Erosion began to wear them down. Today the exposed rock in Blue Mounds is a limestone called Galena dolomite, which is a specific kind of limestone containing some magnesium. Cave of the Mounds itself began to form about a million to a million and a half years ago when the Galena dolomite was still beneath the water table. The water table is defined as that level below Parrot formationwhich all of the rock is saturated with water. Rock above the water table contains air spaces, while rock below the water table has all its spaces filled with water. Often the top layer of the water table becomes acidic because rain water and melting snow absorb carbon dioxide as they seep through surface soils. The water combines with the carbon dioxide to form a weak carbonic acid, which can dissolve limestone and create cavities in the rock.

When a major crack lets large amounts of acidic water into the limestone below the water table, large amounts of rock dissolve along this crack. This is what happened at Cave of the Mounds. The cave was formed along a major crack which can be seen today. This crack is called the "lifeline" of the cave. The story of Cave of the Mounds does not end with the dissolution of limestone to form the hollow cavern. Even as the dolomite beneath the ground was being dissolved to form the cave, surface streams were eroding deeper and deeper valleys in the landscape. Calcite CrystalsAs the stream levels lowered, so did the water table. Eventually, the water table dropped below the level where the cave had been formed. Now the large natural cavity far below the earth’s surface was filled with air. Now a new stage in the life of the cave could begin. When surface water seeps through soil and then through porous limestone rock, it dissolves small amounts of limestone. Every droplet of water entering the cave below carries dissolved calcium carbonate. As the water drops enter the air-filled cave, this calcium carbonate is precipitated into the form of speleothems. Each drop leaves calcite crystals on the cave ceiling or walls or floor.

The crystals adhere to each other and grow into different kinds of formations. Eventually, stalactites reach down from the ceiling, stalagmites tower upward from the floor and sheets of flowstone cover the walls. Speleothems grow slowly. The rate of growth depends on how fast the water flows and on how much dissolved calcium carbonate it contains. It can take from 50 to 150 years to deposit a cubic inch of "cave onyx." Stalactites are speleothems which form on the ceiling of a cave. All stalactites begin as hollow circles when crystals of calcite form around the outer surface of a droplet of water hanging form the ceiling. As each new drop of water appears, it leaves another crystal ring. Soon long crystal soda straws hand from the ceiling. These tubular stalactites grow into cones of icicles if the initial tube becomes plugged and the crystals form around its outer surface. Sometimes water trickles along the cave’s ceiling and walls leaving thin trails of crystals. Each new trail builds upon prior ones to shape ribbon stalactites. Various minerals in the water create the many colors in the speleothems.

Reddish brown colors are oxides of iron; blue and grey colors are manganese oxides. Calcite sometimes forms lily pads or cave rafts on standing pools of water. These occur when a light plate of calcite crystals is held in suspension on the water’s surface. When the crystal plate becomes too heavy, it sinks; other plates form and fall upon one another successively until they make a pad or a raft. As water drips onto the exposed pad, it may form a stalagmite. Then the whole structure looks like a lily pad. Speleothems made of pure calcite with few other added minerals are light colored and translucent when exposed to light. Here crystals of calcite have built on one another to form a single large beautiful parrot-shaped crystal. Helectites are strangely shaped stalactites which grow sideways as well as downward. They seem to defy the laws of gravity. Tiny and rare are the oolites or cave pearls which form as the bottom of small pools of water. Grains of sand act as catalysts for the deposit of calcite crystals. Chambers of curving rock disappear into the distance underground.

The shapes and colors of the walls and ceiling are mirrored in a large reflecting pool, as if in a dream river. Anyone looking down this long tunnel begins to wonder where else the Cave leads, whether the rooms we visit are part of a much larger cave system with unseen possibilities of beauty and color. To date, efforts to find the link between the known passageways of Cave of the Mounds and other possible caves have been unsuccessful. However, the hope of uncovering other vistas like the dream river room remains real. While we dream of additional caves, we strive to cherish the beauty which has already been revealed. The Cave is a treasure to be shared. But, if it is to be shared with future generations, it must be carefully preserved. The beauty of the Cave makes it imperative the we remember the motto used by cavers everywhere: "Take nothing but pictures, leave nothing but footprints, kill nothing but time." To learn more about cave science and conservation, visit the National Speleological Society . To learn more about America's Show Caves, visit the National Caves Association . Cave of the Mounds is proud to serve a wide variety of groups...

Cave Formations Cave Formations Blog Cave Formations Cave formations are called speleothem, from the Greek word "spelaion", cave and "thema" meaning deposit. Almost all of them are made of calcite, the crystal of calcium carbonate. Different minerals and different movements in the water account for an incredible variety of cave formations. As water saturated with calcium carbonate drips through the ceiling of a cave, successive rings of calcite crystals form a tiny tube, a soda straw. If the tube fills, water flows down the outside and the calcite deposits thicken to become a stalactite. Water dripping onto the floor builds stalagmites, which in time may join stalactites to form a column. Water drizzling along a slanted ceiling builds delicate sheets of rock, called cave draperies or curtains. The deposits begin as winding trails of calcite, which later extend downward and thicken. The white portions are almost pure calcite, while other minerals, mostly iron, make the orange and red stains. When water seeps through tiny fissures in the bedrock, it can build incredible unlikely formations called helictites. Water is forced up its tiny central tub, forming a crystal at the tip.

Other speleothem grow on cave pools. Thin layers of calcite forms on the surface of pools as they evaporate. As they float, more and more calcite attaches to it in circular patterns. These "cave rafts" continue to float on the surface of the water as long as it is undisturbed until they reach a weight that pulls them under. Thicker deposits, called shelfstone form where the surface of the water touches the sides of the cavern or submerged columns. In shallow pools fed by dripping water, cave pearls may form. These small spheres are produced by layers of calcite forming around a grain of sand, much like oysters make the pearls they are named after. The agitation of the dripping water makes the pearls almost round and keeps them from sticking to one another or to the bottom of the pool. Flowerlike structures can grow. Crystals of calcium sulfate percolate through porous rock. As new crystals are formed from behind, the flower may grow in a variety of shapes. Large crystals may form in underwater chambers. What is Calcium Carbonate? (with pictures) What is Calcium Carbonate?

Last Modified Date: 28 December 2016 Copyright Protected: Top 10 unbelievable historical concurrencies Calcium carbonate is an important chemical compound made up of one atom of calcium bonded to one atom of carbon and three atoms of oxygen . Its molecular formula is CaCO3. Common names for this compound include limestone , calcite , aragonite, chalk, and marble, and while all contain the same substance, each has different processes underlying its formation. Calcium carbonate is used in cements and mortars, producing lime, in the steel industry, glass industry, and as an ornamental stone. This compound usually looks like a white powder or stone. It will fizz and release carbon dioxide upon contact with a strong acid, such as hydrochloric acid. After the carbon dioxide is released, the remainder is calcium oxide (CaO), commonly called quicklime . When calcium carbonate comes into contact with water saturated with carbon dioxide, it forms a soluble compound, calcium bicarbonate. Underground, this often leads to the formation of caves. The reaction is as follows: CaCO3 + CO2 + H2O → Ca(HCO3)2 Calcium carbonate becomes marble when highly compressed and heated deep underneath the Earth’s surface.

In caves, when dissolved by the above chemical mechanism, it creates magnificent speleothems: cave formations such as stalagmites, stalagmites, curtains, and dozens of others. There are many mineral formations characteristic of this compound, but one of the most common forms is the scalenohedron, or “Dogtooth Spar,” for its resemblance to the canine tooth of a dog. Ad In the form of calcite, this material has an interesting optical property: double refraction. This occurs when a ray of light enters the crystal and splits into distinct fast and slow beams. When an observer looks through the crystal, he or she sees two images of everything behind it. Calcium carbonate possesses other unusual properties, such as fluorescence and triboluminescence. This means that, when combined with a small amount of manganese and put under a UV light , it glows bright red. Under some conditions, the glow even persists when the UV light is removed. Triboluminescence, the property of demonstrating light when pieces of crystal are struck against each other, is more difficult to demonstrate, but it has been noted.

Ad anon159229 Post 6 Is it possible to remove the calcium carbonate in hard water by precipitating it out of solution and then physically removing it? I have water that is over 100 grains hard and I am currently using a lot of salt to soften it. I wondered if there was a better solution. anon127807 Is Calcium carbonate alone UV absorbing? anon111647 Post 4 I've heart calcium carbonate can be used for soil erosion. How does that work? How does it compare with the use of straw and excelsior (wood fiber)? Also, would it be advantageous to use calcium carbonate for soil erosion in arid regions where there is little chance of establishing grass or other vegetation? GenevaMech Post 3 @ COmparables- I can help you out. Acid rain (carbonic acid H2CO3) is simply carbon dioxide (CO2) dissolved in water (H2O). Carbon dioxide gas dissolves into the water vapor in the clouds and falls to the ground as a slightly acidic solution. Acid rain is not a new phenomenon it has been falling to earth since life has existed.

The acid rain has just become more acidic since the industrial revolution, so the controversy surrounding acid rain is about the increased acidity due to anthropogenic causes. In the 660,000 years before the industrial revolution, carbon concentrations in the atmosphere have never exceeded 350 parts per million. Under current conditions, dissolution of calcium carbonate and the precipitation of calcium bicarbonate back to calcium carbonate would simply be accelerated. Caves would form faster, stalactites would hang down further, and stalagmites would reach higher towards the roof of caves. Comparables Post 2 @ Highlighter- If acid rain dissolves calcium carbonate then why are most of these caves thousands of years, if not millions of years, old? Isn't acid rain a fairly recent phenomenon? If you can explain this a little more I would appreciate it. highlighter Post 1 The chemical process of calcium carbonate precipitation is what forms the many of the caves, stalactites, and stalagmites that you see below the earth’s surface. The dissolution of the calcium carbonate in by carbonic acid (acid rain) causes the calcium carbonate to form a solution. The dissolution of calcium carbonate forms the caves and caverns underground.

This dissolved calcium carbonate forms calcium bicarbonate, which then precipitates out of solution to become an insoluble solid (it is only soluble in a carbonic acid, not pure water). This precipitation is what forms the stalactites and stalagmites that form within caves (and the lime scale around your bathtub that is so hard to scrub off). The interesting thing about this chemical process is that the precipitate becomes more stable at colder temperatures because there is less carbon dioxide dissolved in the water. Post your comments Limestone caves - Australian Museum Australian Museum About us Limestone caves Caves form in limestone (calcium carbonate), and occasionally in dolomite (calcium magnesium carbonate), when water containing dissolved carbon dioxide (carbonic acid) seeps into rock crevices and joints. The carbon dioxide comes from decaying organic matter in soil, and also directly from the atmosphere. This slightly acidic water dissolves the rock, forming cavities which can enlarge and join up to make larger cave systems of interconnected chambers. An underground water flow can develop when many rain-fed subsurface drainages join up, or a river can be captured by an open cavity collapse structure (sink hole or doline) and flow underground.

This leads to further enlarging and sculpturing of the caves by chemical and physical weathering. Gravel, sand, silt and clay can be deposited in the caves from outside, or fine sediments from internal springs may build up. This dissected and dissolved landform with a complex groundwater system is called karst. Cave decorations When underground rivers work deeper, or water-filled cavities are drained, the resulting free spaces (often the higher or older chambers) can be decorated with various types of crystalline calcium carbonate formations. After passing through limestone, the acidic water contains calcium carbonate in soluble form, now present in solution as calcium bicarbonate. When the solution loses carbon dioxide, it deposits solid calcium carbonate again. The resulting mineral is usually calcite, but occasionally a calcium carbonate with different crystal form can grow (aragonite). The solution can lose carbon dioxide when degassing through direct exposure to air, especially when it splashes, or flows over impediments. The resulting cave formations have a waxy, glistening appearance. Loss of carbon dioxide through evaporation plays a much lesser role, usually in areas of high airflow near cave entrances, but the resulting cave formation usually look dull and chalky.

Bacterial and algal colonies can also play a role in deposition of calcium carbonate. Cave deposits or decorations are called speleothems. How a cave is decorated depends on whether the water drips, seeps, flows or sits in pools. Dripstones Straws grow from hanging drops of water. The crystals form on the outer rim of each successive drop, building up a hollow tube with internal diameter of a few millimetres. Straws sometimes reach lengths of over 6 metres. Stalactites grow from water dripping off a cave roof. A long, thin hollow tube, a straw, forms first, but its internal channel becomes blocked, forcing water to flow over its outer surface, depositing successive layers of calcite, resulting in a stalactite with typical pointed carrot shape. Stalagmites grow from splashing drips beneath the stalactites. Stalagmite shapes tend to be 'stumpy' or rounded, compared to the more pointed shape of stalactites. Columns result when a stalactite and its corresponding stalagmite meet. Shawls grow from water trickling down sloping surfaces. Layers of calcite build up into fluted curtains. Seepstones Helictites seem to defy gravity.

They grow when water slowly seeps through porous roof or wall surfaces, producing tiny droplets that precipitate calcite in the form of fine tubes with minute internal channels. The water flows through the tubes by capillary action, and changes in the direction of growth may be due to blockages in the internal channels. As the calcite grows from the tip at various angles, interesting twisted shapes result. Flowstones Flowstone forms from layers of calcite deposited when thin films of water flow down walls and across cave floors. Some resemble 'frozen waterfalls'. Flowstone often forms over gravel and silt left behind by underground rivers. When this material is washed away to leave an undercut, canopies of flowstone are left unsupported. Rimstone dams build up on slopes as slow-moving water flows over them. Bumps on the sloping surface promote turbulence and assist carbon dioxide loss. The resulting low walls can hold back water to form a pond. Poolstones Rafts are formed from thin skins of crystalline calcite which float on the surface of a pool. Calcite crystals grow as 'dog-tooth spar' when caves or smaller cavities are filled with still water. These solutions are saturated with dissolved calcium carbonate and can precipitate crystals with perfect geometrical shapes.

They stop growing when the water drains out. Calcite can crystallise as a very thin and fragile shell around air bubbles, which will eventually sink to the bottom of the pool. Cave pearls are formed when calcite grows around small grains in a pond, adding layer after layer to form small spheres. Ross Pogson , Collection Manager, Mineralogy Last Updated: Cave Terminology You Are At: AllSands Home > Science &GT; Cave terminology Cave Terminology A list of cave terminology for you speleologists! Anastomoses - are one of two very common characteristics of cave walls. They are small winding tubes that interconnect and are often found along bedding plane partings. They can sometimes be seen on flat ceilings and are often mistaken for solution pockets. Blindfish - are translucent fish that have no eyes. Amblyopsis spelaea is the famous blindfish that can be found in Mammoth Cave and could not survive outside the cave. Blind Crayfish - are crayfish that do not have eyes. They have adapted to the total darkness found in the cave. Calcite - is a mineral composed of calcium carbonate. Calcite begins to dissolve when carbonic acid from rainwater comes in contact with it.

With this process it would take hundreds of thousands of years to form a large cavern within a cave. Carbonic Acid - is a weak acid formed by the interaction of carbon dioxide and water. It can dissolve limestone. Cave - is an underground cavity that is formed naturally by the dissolving action of acidic groundwater. Cave Coral - are small knobby clusters that are formed by seeping water. They are also referred to as "cave popcorn." Cave Cricket - is a spiderlike cricket that lives in caves and on the surface. Cave Popcorn - is formed when calcium carbonate found in groundwater forms cauliflower shaped clusters that are on cave walls by splashes from waterfalls. This is also called "Cave Coral." Cave Shrimp - are translucent freshwater shrimp with no eyes. They are an endangered species that can only be found in Mammoth Cave in Kentucky. Cavern - is a large cavity found within a cave. Chamber - is the largest type of cavity in a cave. It is considerably wide and long but not necessarily great in height. Claustrophobia - is the fear of closed in spaces. Columns - are formed when stalactites join with stalagmites to form a single structure.

Dark Zone - is the area of a cave that never receives daylight. Domes - are formed by waterfalls in a cave and are holes that you can look up into and see the cave ceiling. Drapery - is a mineral deposit that is formed when water deposits calcite in thin sheets that hang in delicate folds. Dripstone - are mineral deposits that are found where stone of the cave's roof has been eroded and water then seeps into the cave's passageways. Epsomite - is a small amount of crystallized salt that forms hairlike tendrils from floors, ceilings, and walls. They form more in winter months with low humidity and then disappear as the humidity rises. Flowstone - is a secondary deposit of calcium carbonate or calcite that is precipitated by groundwater. It often resembles frozen waterfalls with sheets of calcite that resemble frosting on a cake. Fissure - is an open crack in rock or soil. Fossil - is a plant or animal trace that has been preserved in rock or sediment. Grotto - is a richly decorated room in a cave with moderate dimensions. Groundwater - is any water which floes beneath the earth's surface. Gypsum - is made of calcium sulfate.

It is a snowy white mineral decoration that can take the shape of flowers, tendrils, or sheets that can cover ceilings, walls, or floors. Helictites - have knotted or twisted shapes due to slowly seeping water that causes a thin film of calcium carbonate to stick to the side of a cave formation in a random manner. Limestone - is made up of shells that gathered on a sea floor and later hardened into layers of rock. It is composed mainly of calcium carbonate. Mirabilite - is a small amount of crystallized salt that forms hairlike tendrils from walls, ceilings and floors of caves. They appear more frequently during winter months with low humidity and disappear in warmer weather with higher humidity. Passages - are cavities in caves that are longer than they are wide or high and they may join larger cavities. Pits - are vertical openings in floors of cave passages that were created by collapsed rock or solutional activity of descending water. Rimstone Dams - are steplike terraces along streams and on cave floors that contain pools of calcium carbonated water. Rooms - are wider parts of caves than passages but not as large as chambers.

Saltpeter - was a salt that was mined from caves and used in the production of gunpowder. Scallops - are one of the most common characteristics on cave walls. They are spoon-shaped hollow areas that have been dissolved in limestone floors, walls, and ceilings. Sediment - is material that was recently deposited by wind, water, ice, or precipitated from water. Sinkholes - are "bowl-shaped" depressions that are created by the collapse of an underground cave. Soda Straws - are hollow stalactites that look like traditional soda straws in their size and shape. Speleothems - are cave formations or mineral deposits that are formed by the deposition of minerals in a cave. Spelunker - is a person who enjoys exploring caves. Speoleologist - is a person who studies the geology, formations and environments of caves and cave systems. Stalactite - is a cave formation that develops from the cave ceiling and hangs downward. Stalagmite - is a cave formation that develops from the cave floor and protrudes upward. Travertine - is a traveling rock formation that is created by calcium carbonate being redeposited.

Troglobites - are animals that live their entire life cycle within a cave. Troglodyte - is a human cave dweller. Troglophiles - are animals that like living in caves but do not depend on the cave's environment as part of their survival. Trogloxens - are animals that visit caves occasionally but live above ground. Windows - are irregular openings through thin rock walls of caves. Cave Formations (Stalactites, Stalagmites, Soda Straws, Columns, Shields, etc.) Cave Formations (Stalactites, Stalagmites, Soda Straws, Columns, Shields, etc.) Cave formation is the process by which a cave is created. Cave "formations" are the unusually-shaped rocks that you see inside a cave, such as stalactites. As the water level drops and a cave forms underground, the water-filled passages gradually become air-filled. (The fancy terms: a "phreatic" channel becomes a "vadose" channel.) Most of the surface water reaching the top of the air-filled passage will continue to drip down into the stream of water that emerges as a spring.

Once the humidity in those passages drops below 100%, however, some of the surface water will evaporate into the atmosphere of the cave. When a drop of water evaporates underground in a cave, it may leave behind a tiny deposit of the calcium carbonate that the drop had dissolved during its journey down from the earth's surface. Thin films of calcite can grow into half-inch wide "soda straws" with a drop of water on the bottom. Such soda straws can grow over a foot long. Once a piece of grit or a grain of calcium carbonate blocks the water's flow through the middle of a soda straw, the film of water will drip along the outside of the formation. This process creates - over hundreds or thousands of years - the stalactites that hang from a cave ceiling. If the drips of water fall to the cave floor before evaporating completely, they carry a portion of the dissolved calcium carbonate with them. When the water droplets then evaporate on the cave floor, they form stalagmites that grow upwards from the floor of the cave to the ceiling. Stalagmites are often located just below a stalactite, and when the two finally grow together a "column" is formed.

Other cave formations include flowstone, cave coral, helictites, and a variety of other shapes that reflect the rate of evaporation, the chemical composition of the local rock, and even tiny wind currents in the cave. The colors in the formations reflect the local minerals. Water flowing through iron ores (hematite and limonite) will create reddish/yellow bands alternating with the white calcite, creating formations that resemble slabs of bacon with layers of fat and lean meat. Manganese will create black streaks on the cave walls and a black coating on the rocks in a flowing stream. The rate at with formations grow varies, but can be rapid. Limestone and marble buildings less that 100 years old (such as the Lincoln Memorial) may have soda straws several inches long, showing that the chemical process of dissolving calcium carbonate is not restricted to caves and gravestones. cave formations (speleothems) at Grand Caverns (Rockbridge County) Cave formations are rarely created on the earth's surface, because wind and rain erode the soft calcium carbonate faster than it can be created through evaporation. There are a few locations where the calcium in the water may be deposited outside a cave or spring.

The most-visited such site is Mammoth Hot Springs at Yellowstone National Park. At Falling Springs near Covington, at Falls Ridge Preserve in Montgomery County, and at Natural Bridge in Rockbridge County, water emerges from a spring still loaded with dissolved limestone. It deposits travertine (a form of calcium carbonate) along the edge of the pools and on the streambed just below the spring, and can coat sticks and leaves with a film of rock within just a few months. The formations are fragile, however. One careless step by a visitor can destroy decades of rock formation. In addition, cave visitors are warned "don't touch" because the oils on our fingers will block the continued growth of a cave formation. The water droplet with its thin film of calcite will slide off the formation, before it can evaporate and deposit another addition to the "living rock." Some caves are exposed when erosion from the surface intersects the cave, removing the roof and exposing the cave formations to wind and rain. It takes only a short time (a few decades) to erode away the obvious signs that there was once a cave at that location.

There's a small stream entering the Shenandoah River about a mile downstream of the Route 50 bridge, where the old formations are just barely visible today along a streambank that was once a cave passage. Natural Bridge - the last remains of a cave roof Cave formation – Maropeng – Official Visitor Centre Home » Visitors » Sterkfontein Caves » Sterkfontein exhibition » Exhibition guide » Cave formation Cave formation The caves at Sterkfontein were formed in dolomitic limestone over millions of years. They began to form as early as 20-million years ago. Most caves including Sterkfontein – are formed by the dissolving action of weakly acidic rainwater, which seeps into the soluble rock through the soil. Visitors to Sterkfontein learn about the formation of caves In ancient Neoarchaen times, 2.58-billion years ago, dolomite formed in the bed of a shallow sea. Within the last 20-million years, the Sterkfontein Caves were formed within the dolomitic rock. Slightly acidic groundwater dissolved solution cavities beneath the water table. This zone beneath the groundwater surface or water table is known as the phreatic zone.

Over time, the water table dropped and the caves became air-filled voids in which stalactites and stalagmites could form. Water from the surface percolating through cracks in the dolomite absorbed calcium carbonate. On reaching the cavern ceiling, carbon dioxide was released, and a thin film of calcium carbonate was deposited. The deposits built up over time to form stalactites and other formations. Stalactites and stalagmites The term stalactite comes from the Greek word stalaktos, which means “dripping”, because these other-worldly formations are produced by “drips” from the ceilings of limestone caves. Water reacts with chemical elements in the ground and rock, and seeps slowly through the roof of the cave, depositing calcium carbonate, which hardens and builds up over time to form a stalactite. Stalagmites are corresponding formations on the floors of caves, rising up over time as drops of water, rich in calcium carbonate, fall from the roof of the cave. The term stalagmite comes from the Greek word, stalagma, to “drop”.

How to remember the difference StalaCtite has a “c” for “ceiling” StalaGmite has a “g” for “ground” Stalactites hang “tite” to the ceiling above Stalagmites “mite” grow all the way to the ceiling Bones and breccia in caves Solution and roof collapse created entrances to the caves in the form of vertical shafts. Soil, rocks, bones and vegetation fell in from the surface – the animals and plants from which fossils formed did not actually live in the caves. Example of a fossil of a sabre-tooth cat encased in breccia, found in the Sterkfontein Caves The bones that found their way into these shafts were often just fragments left by the activities of predators and scavengers around the shaft entrances. But sometimes – far less often – a whole animal would fall down a cavity and be fossilised in the infill. The famous australopithecine skeleton “Little Foot”, which was found deep inside a Sterkfontein grotto, is an example of this.

Over time, the material that fell into the cave shafts built up to form talus cones, which look like giant, inverted ice-cream cones, on the cave floor. These deposits were cemented by lime-charged water to form concrete-like breccia, a type of rock. Bones within these talus cones were mineralised by calcium carbonate and stained with manganese and iron from the dolomitic soil. Sometimes floor collapses into lower caves or erosion by surface water disrupted the stratified layers, mixing the deposits. This means that even if some deposits are deeper than others, they are not necessarily older than those nearer the surface. The bulk of the Sterkfontein cave deposits were not disrupted in this way. University of the Witwatersrand geologist Professor Tim Partridge classified the deposits from oldest to youngest as geological Members 1 to 6 of the Sterkfontein formation. The infills span a period from about 4.2-million years ago to less than 200,000 years ago. The different infills have characteristic fossil and/or artefact (stone tool) content. Over time, the water table dropped and the caves became air-filled voids in which stalactites and stalagmites could form.

Water from the surface percolating through cracks in the dolomite absorbed calcium carbonate. On reaching the cavern ceiling, carbon dioxide was released, and a thin film of calcium carbonate was deposited. The deposits built up over time to form stalactites and other formations. Limestone Features - Geo for CXC CXC Results Limestone Features Limestone is the name given to rock which is composed mainly of calcium carbonate. Calcium carbonate is a chemical compound of calcium, carbon and oxygen. The chemical formula for calcium carbonate is CaCO3. Limestone is a sedimentary rock which is formed underwater. Some limestone consists mainly of coral or the shells of other small marine creatures. Limestone may also be precipitated from seawater. Limestone is a permeable rock. This means that water can enter limestone through pores, joints or cracks in the rock. Another characteristic of limestone is that it can be slowly dissolved by water. When groundwater or rainwater absorbs carbon dioxide, it becomes a weak acidic solution which is especially effective at dissolving limestone. Because of these simple facts, wherever limestone is in contact with rainwater or groundwater, some interesting limestone features tend to develop.

Common Limestone Features Sink holes: A sink hole (or swallow hole) is a natural depression or hole in the Earth’s surface commonly found in limestone areas. They are formed when joints or fissures in the rock are enlarged by carbonation or when the roof of an underground cavern collapses. Sometimes a river or stream may “disappear” down a sink hole and continue flowing underground. The photo below shows a large sinkhole located in China. This limestone feature is a large sinkhole known as the Xiaozhai Tiankeng Caves: A cave is a naturally occurring underground hollow or passage, especially one with an opening to the surface of the Earth. Caves often form in limestone areas when underground water dissolves the rock, forming tunnels passages and even large caverns. There are several caves in Barbados, the most famous of which is Harrison’s cave. Part of Harrison’s Cave can be seen in the photo below. Limestone Features seen at Harrison’s Cave, Barbados Many interesting limestone features can be found within limestone caves. Some common ones are stalactites, stalagmites and pillars. Stalactites:Water dripping from the ceiling of a cave contains dissolved calcium carbonate. Some of this calcium carbonate may be deposited on the ceiling of the cave.

Over time the deposition of calcium carbonate will form an elongated feature which hangs down from the ceiling. This feature is known as a stalactite. Several stalactites can be seen in the photo above. Stalagmites: As water drips from the ceiling onto the floor of the cave, calcium carbonate may be deposited on the floor of the cave. Over time this may form an elongated feature which rises vertically from the cave floor. This feature is known as a stalagmite.Several stalagmites can be seen in the photo above. Note: A simple way to avoid confusion is to remember that stalactite has a “c” for “ceiling” and stalagmite has a “g” for “ground”. Pillars: A stalagmite may form directly below a stalactite as water drips from the ceiling of the cave onto the floor. The stalactite may continue to grow downwards and the stalagmite may continue to grow upwards until the two limestone features eventually meet. When this happens they form a new feature known as a pillar or column which extends all the way from the ceiling of the cave to the floor. A limestone pillar can be seen in the photograph below.

This limestone pillar is found in the Cango Caves in South Africa Karst Landscapes In many limestone areas, the chemical weathering processes of solution and carbonation have produced distinctive landscapes known as karst landscapes. Karst landscapes are dominated by features such as sinkholes, disappearing streams and caves. One well known karst landscape in the Caribbean is the Cockpit Country in Jamaica. On the map of Jamaica below, the Cockpit Country is shown as an area outlined in pink. Map of Jamaica showing Cockpit Country, (Map by DieBuche) The Cockpit country is a large area with many small hills and depressions. This karst landscape was formed in an area with white limestone. In this area, the rock has many joints. These joints cross each other as some run from east to west and others run generally from north to south. Water collects in these joints. Therefore the rock near the joints is dissolved relatively quickly forming depressions. Small hills form in areas which are further away from the joints as the rock in these areas is not dissolved as quickly. The photo below shows a small part of the Cockpit Country. The Cockpit Country, Jamaica There are many caves and sinkholes within the Cockpit Country.

No rivers or streams can be found on the surface in the area because they have all disappeared into swallow holes and flow underground through caves.

Question: What are the formations of calcium carbonate which hang down from the roof of a cave?
Answer: Stalactites