Cave formations stalagmite

Figure 7.1 Cave formations are caused when rainwater and carbon dioxide mix and form a weak carbonic acid, which then dissolves the calcium carbonate of limestone beneath the earth, allowing for cave formation. The photo shows stalactites and stalagmites and other formations at Luray Caverns in Virginia.

Stalagmites are cave formations that start on the floor and grow upward. These formations are caused when water that contains dissolved limestone drips from the ceiling of the cave and lands on the same spot. Sometimes, water dripping off of a stalactite will actually form a stalagmite directly below it. Eventually, a column forms when the stalactite and stalagmite meet. This feature can take thousands or even millions of years to form. 

FIGURE 10.3 Stalactites hang from the roof of a cave and stalagmites grow from the floor. Both are caused by the formation of carbonates from the more soluble hydrogen carbonates carried in to the cave by groundwater. 

Stalagmite A cone-shaped cave formation that is formed on the cave floor when water containing dissolved calcium carbonate drips from a cave s ceiling. 

Solution caverns or caves often contain deposits of recrystallized calcium carbonate, usually in the form of the mineral aragonite. Stalactites, stalagmites, and other cave formations are called speleothems. Created gradually by the precipitation of aragonite from groundwater, many speleothems display a layered structure. Recent study shows that bacteria and other simple life forms may contribute to the formation of cave deposits. 

Such caves are formed by the action of acidic groundwater on limestone deposits.The icicle-like formations (stalagmites and stalactites) in the caves are caused by the reprecipitation of calcium carbonate as carbon dioxide in the solution equilibrates with the surrounding air. 

The solubility of the carbonate in water containing carbon dioxide causes the formation of caves with stalagtites and stalagmites and is responsible for hardness in water. Other important compounds are the carbide, chloride, cyanamide, hypochlorite, nitrate, and sulfide. 

Carbonic acid (HjCO ) is produced by dissolving carbon dioxide in water. When formed under pressure, it is the gas used in carbonated drinks. In nature, it dissolves the limestone in caves, resulting in the formation of stalactites and stalagmites. It is corrosive as are other acids, although it is considered a rather weak acid. 

This process and its reverse account for the formation of limestone caves and the stalactites and stalagmites found there. The acidic water (containing carbon dioxide) dissolves the underground limestone deposits, thereby forming a cavern. As the water drips from the ceiling of the cave, the carbon dioxide if ->st... 

The completely recrystallized flowstone is of various types, ranging from nearly pure glassy calcite to heavily clay-stained formations. Most is in the form of wall-flowstone or half-stalactites. Flowstone cave bottom crusts and massive stalagmites are also found, whereas true stalactites appear to be absent. As mentioned above, with very few exceptions most of the flowstone is found associated with conglomerate. Flowstone crusts survive on the walls of nearly completely washed-out caverns, or in the form of highly corroded flowstone dints . Much of the flowstone appears either within confirmed former caves or in situations where the presence of a former cave is at least strongly implied. 

Calcium carbonate forms limestone, one of the most common rocks on Earth. It also forms stalactites, stalagmites, and many other types of formations found in caves. When calcium carbonate is heated, it decomposes to form solid calcium oxide and carbon dioxide gas. 

The flowing water becomes saturated with calcium carbonate as carbon dioxide is swept away, the reverse reaction becomes favored, and limestone is deposited in formations whose shapes are governed by the path of the flowing water. Stalactites and stalagmites are examples of similar formations found where water saturated with calcium carbonate drips from the ceiling to the floor of caves over eons. 

Stalactites and stalagmites in caves are formed from solutions, as shown in Figure 4. First, minerals dissolve in water as it flows through rocks at the top of the cave. This solution of water and dissolved minerals drips from the ceiling of the cave. When drops of the solution evaporate from the roof of the cave, the minerals are left behind. They create the hanging rock formations called stalactites. When drops of the solution fall onto the floor of the cave and evaporate, they form stalagmites. Very often, a stalactite develops downward while a stalagmite develops upward until the two meet. One continuous column of minerals is formed. This process will be discussed later. 

Acid in the Environment Carbonic acid plays a key role in the formation of caves and of stalactites and stalagmites. Carbonic acid is formed when carbon dioxide in soil is dissolved in water. When this acidic solution comes in contact with calcium carbonate—or limestone rock—it can dissolve it, eventually carving out a cave in the rock. A similar process occurs when acid rain falls on statues and eats away at the stone, as shown in Figure 16. When this acidic solution drips from the ceiling of the cave, water evaporates and carbon dioxide becomes less soluble, forcing it out of solution. The solution becomes less acidic and the limestone becomes less soluble, causing it to come out of solution. These solids form stalactites and stalagmites. 

An understanding of precipitation reactions is useful in many ways. They may explain natural phenomena, such as the formation of stalagmites and stalactites in caves they are simply precipitates in rocklike form. Kidney stones may result from the precipitation of calcium oxalate (CaC204). The routine act of preparing a solution requires that none of the solutes will react to form a precipitate. 

The very form and function of the earth is a consequence of a variety of complex equilibria. Stalactite and stalagmite formations in caves are made up of solid calcium carbonate (CaC03). They owe their existence to an equilibrium process described by the following equation ... 

Stalactites and stalagmites in the Drapery Room at Mammoth Cave in Kentucky. These formations are created when carbonate minerals dissolve in groundwater acidified by carbon dioxide and then solidify when the water evaporates. 

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