what is a speleothem? course hero

What is a speleothem in a cave?

The term speleothem refers to the mode of occurrence of a mineral —i.e., its morphology or how it looks—in a cave, not its composition (Hill, 1997). For example, calcite, the most common cave mineral, is not a speleothem, but a calcite stalactite is a speleothem.

Why do caves have speleothems?

Caves vary widely in their displays of speleothems because of differences in temperature; overall wetness; and jointing, impurities, and structures in the rocks. In general, however, one thing caves do have in common is where speleothems form.

How are stalagmites formed?

Stalagmites are convex floor deposits built up by water dripping from an overhead stalactite or from the cave ceiling. Because falling water droplets tend to splash, stalagmites spread out as they gradually build up from the floor. Hence, they do not have central, hollow tubes like stalactites. Stalagmites are usually larger in diameter than the stalactites above them and they generally have rounded tops instead of pointed tips.#N#“That which drops” is the Greek meaning of stalagmites. When a drop of water falls from the ceiling or stalactite, it still has some material left in solution. When the drop hits the floor, carbon dioxide is given off and carbonate material is precipitated as a mound below the point of dripping; or, if a noncarbonate mineral, evaporation causes precipitation of mineral material.#N#Stalagmites can assume a fascinating variety of shapes and people have compared them to broomsticks, totem poles, toadstools, bathtubs, Christmas trees, beehives, coins and buttons, and even fried eggs!

How do calcite draperies form?

When water drops flow down a sloped ceiling before dripping to the floor, calcite can build up in a line. These lines gradually form “draperies” or “cave bacon.” This type of speleothem is found in almost every cave in the world and is universally popular because of the close resemblance to its namesake (Nelson, 2000). Iron oxide or organic solutions form the baconlike stripes. As the formations grow, small undulations in the bedrock cause the draperies to become slightly curved. With time these curves become more and more accentuated so that the draperies become highly folded or furled along their lower edges. Dripstones may form at the bottom of draperies where the furls are steep enough for water droplets to fall to the floor.

What are stalactites made of?

A stalactite may be made of other minerals, such as halite or gypsum. Classifying speleothems is tricky because no two speleothems are exactly alike. Nevertheless, speleologists have taken three basic approaches: classification by morphology, classification by origin, and classification by crystallography.

What is coralloid speleothem?

Coralloid (or corallite or cave popcorn) is a catchall term describing knobby, nodular, botryoidal, or corallike speleothems. After stalactites, stalagmites, and flowstone, coralloids are probably the most common speleothem type (Hill, 1997). Coralloids range in size from tiny beads to globular masses a few feet in diameter. Coralloids include cave popcorn, grapes, knobstone, coral, cauliflower, globularites, and grapefruit. Coralloids can form both in the open air and under water.

What are the features of caves?

The features that arouse the greatest curiosity for most cave visitors are speleothems. These stone formations exhibit bizarre patterns and other-worldly forms, which give some caves a wonderland appearance. Caves vary widely in their displays of speleothems because of differences in temperature ; overall wetness; and jointing, impurities, and structures in the rocks. In general, however, one thing caves do have in common is where speleothems form. Although the formation of caves typically takes place below the water table in the zone of saturation, the deposition of speleothems is not possible until caves are above the water table in the zone of aeration. As soon as the chamber is filled with air, the stage is set for the decoration phase of cave building to begin.

What is speleothem in caves?

The usual definition of speleothem excludes secondary mineral deposits derived from concrete, lime, mortar, or other calcareous material (e.g. limestone and dolomite) outside the cave environment or in artificial caves (e.g. mines, tunnels), which can have similar shapes and forms as speleothems. Such secondary deposits in man-made structures are termed calthemites. Calthemites are often associated with concrete degradation, or due to leaching of lime, mortar or other calcareous material.

How do speleothems form?

Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on their depositional history and environment. Their chemical composition, gradual growth, and preservation in caves make them useful paleoclimatic proxies.

What color are speleothems?

Speleothems of pure calcium carbonate or calcium sulfate are translucent and colorless. The presence of iron oxide or copper provides a reddish brown color. The presence of manganese oxide can create darker colors such as black or dark brown. Speleothems can also be brown due to the presence of mud and silt.

Why are speleothems brown?

Speleothems can also be brown due to the presence of mud and silt. Many factors impact the shape and color of speleothems, including the chemical composition of the rock and water, water seepage rate, water flow direction, cave temperature, cave humidity, air currents, aboveground climate, and aboveground plant cover.

What is the chemical composition of caves?

Most cave chemistry involves calcium carbonate (CaCO 3) containing rocks such as limestone or dolomite, composed of calcite or aragonite minerals. Carbonate minerals are more soluble in the presence of higher carbon dioxide (CO 2) and lower temperatures. Calcareous speleothems form via carbonate dissolution reactions whereby rainwater reacts with soil CO 2 to create weakly acidic water via the reaction:

What are cave minerals made of?

The vast majority of speleothems are calcareous, composed of calcium carbonate (CaCO 3) minerals ( calcite or aragonite ). Less commonly, speleothems are made of calcium sulfate ( gypsum or mirabilite) or opal.

What are stalactites that have a central canal with twig-like or spiral projections that appear?

Helictites are stalactites that have a central canal with twig-like or spiral projections that appear to defy gravity. Include forms known as ribbon helictites, saws, rods, butterflies, hands, curly-fries, and "clumps of worms". Chandeliers are complex clusters of ceiling decorations. Ribbon stalactites, or simply "ribbons", are shaped accordingly.

What are the two materials that form speleothems?

In addition to calcite, other materials which form speleothems are aragonite and gypsum. Aragonite has the same chemical formula of calcite#N#C a C O 3#N#CaCO_ {3} C aC O3#N#​#N#. Difference is in crystalline structure.

What causes a speleothem to grow sideways?

Usually are made of gypsum and exist in many different shapes. Growth direction is caused by gypsum precipitation. Curvatures are caused by variation flux of saturated water.

What are the most common rock formations in caves?

Speleothems are rock formations inside caves, the most known are stalactites and stalagmites. These and other formations are shown in this post.

What are Speleothems in Muppets Tonight?

Speleothems are cave formations that can be produced in the form of stalactites, which hang from the ceiling, and stalagmites, which rise from the ground. Platinum Collection Build Your Own Bundle. Choose up to 7 games.

What are cave formations that can be produced in the form of stalactites, which hang from the ceiling,?

Speleothems are cave formations that can be produced in the form of stalactites, which hang from the ceiling, and stalagmites, which rise from the ground.

What episode does the stalagmite complain about toothache?

A set of two stalactites and four stalagmites appear in a sketch in episode 307 of The Muppet Show, in which one stalagmite complains of a toothache while the rest of the speleothems echo him.

Who performed the stalactites in Muppets Tonight?

The two lead stalagmites were performed by Richard Hunt and Jerry Nelson. In episode 108 of Muppets Tonight, a set of four differently designed stalactites can be seen on the set of Jason Alexander and Gonzo's closing number, " Bats: the Musical .".

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Why are speleothems important?

Since caves exist all over the Earth, speleothems have the potential to become a pivotal land-based climate record. Other land features help fill in the picture of climate in the past. Water marks trace the shorelines of ancient lakes where none exist now.

What is the substance that forms in the speleothem?

Uranium from the surrounding bedrock seeps into the water and forms a carbonate that becomes part of each layer of the speleothem as it forms. Uranium decays into thorium, which sticks to the clay in the bedrock instead of seeping into ground water and from there into the speleothem.

Why do scientists look for similar patterns of growth in speleothems in caves over a broad area?

Scientists must look for similar patterns of growth in speleothems in caves over a broad area to infer that the climate changed. The cross section of a stalagmite reveals a sequence of layers, laid down over time.

What is the name of the cave in New Mexico?

One of the world’s largest underground chambers, the Carlsbad Cavern is resplendent in the intricate finery of the rock formations that form there. Beyond their breath-taking beauty, the formations in Carlsbad and the more than 100 other caves in the area provide a record of rainfall in the southwestern United States.

What rock formations hold information on past rainfall and temperatures?

Spectacular rock formations in Carlsbad Cavern hold information on past rainfall and temperatures. (National Park Service Photo by Peter Jones)

What is the name of the mineral formations in caves?

Geologists refer to the mineral formations in caves as “speleothems. ”. While the water flows, the speleothems grow in thin, shiny layers. The amount of growth is an indicator of how much ground water dripped into the cave. Little growth might indicate a drought, just as rapid growth could point to heavy precipitation.

Why are artifacts important to scientists?

While these artifacts in the Earth are valuable to scientists reconstructing large-scale climate patterns on land , most have been disturbed by subsequent weathering. For a global picture of past climate, scientists also need a consistent record that covers a broad section of the Earth. For that, they turn to the oceans.

Overview

Chemical and physical characteristics

Formation processes

Climate proxies

Types and categories

Calthemites

See also

External links