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A cave is a natural underground void.
Caves are formed by geologic processes. These may involve a combination of chemical processes, tectonic forces and atmospheric influences.
Some caves are formed at the same time as the surrounding rock. These are called primary caves. Lava tube cave at Craters of the Moon Lava tubes are formed through volcanic activity. They are the most common primary caves. Lava flows downhill and the surface cools down and becomes hard. The lava now flows inside its crust, until the eruption ends. The liquid lava inside the crust flows out and leaves a hollow tube. The most important lava tubes are found on Hawaii ( Big Island). Kazumura Cave near Hilo is the longest and deepest lava tube of the world and also the eighth longest cave of the United States.
Blister caves are also formed through volcanic activity.
Secondary caves are formed inside the rock after the rock itself has formed by processes which removes material such as solution and erosion.
Erosion is a mechanical form of weathering which is caused by the abrasive action of wind or water.
Ice cave in Big Four Glacier, Big Four Mountain , Washington, ca. 1920
Solutional caves may form anywhere with rock which is soluble, and are most prevalent in limestone, but can also form in other material, including chalkChalk is a soft, white, porous form of limestone composed of the mineral calcium carbonate. It is relatively resistant to erosion and slumping compared to the clays that it is usually associated with, and so forms tall steep cliffs where chalk ridges meet, dolomiteFor the European mountain range, see Dolomites Dolomite is a mineral (formula CaMg(CO)) consisting of a calcium magnesium carbonate found in crystals and in beds as dolostone. A pure form of dolostone would be rare, however; it usually intergrades with li, marbleThis page is about the metamorphic rock. For the game with little glass spheres see marbles. Marble is metamorphosed limestone, composed of fairly pure calcite (a crystalline form of calcium carbonate, Ca C O). It is extensively used for sculpture, as an, loessLoess is a fine, silty, windblown ( eolian) type of unconsolidated deposit, or, sometimes the term refers to the soil derived from it. It is derived from glacial deposits, where glacial activity has ground rocks very fine ( rock flour). After drying, thes, iceIce is the solid form of water. The phase transition occurs when liquid water is cooled below 0 °C (273. 15 K, 32 °F) at standard atmospheric pressure. Ice can be formed at higher temperatures in pressurized environments, and water will remain a liquid or, graniteGranite is a common and widely-occurring group of intrusive felsic igneous rocks that form at great depths and pressures under continents. Granite consists of orthoclase and plagioclase feldspars, quartz, hornblende, biotite, muscovite and minor accessory, saltFor other meanings of the word salt see salt (disambiguation In chemistry, a salt is a composed of positively charged cations and negatively charged anions, so that the product is neutral and without a net charge. They are typically the product of a chemi, lavaLava is molten rock that a volcano expels during an eruption. Due to its high temperature, lava can be quite fluid when first exuded from a volcanic vent, but eventually solidifies into rock. However, the lava may flow many miles before solidification., sandstone, and gypsum. The most common process of cave formation is karstification, which is the solution of rocks by rain water.
Cave formation in limestone occurs because limestone dissolves under the action of rainwater and groundwater charged with CO2 ( carbonic acid) and naturally occurring organic acids. The dissolution process produces a distinctive landform known as karst and characterized by sinkholes, sinking stream s, and underground drainage.
Limestone solution is the single most important process forming caves and the origin of the great majority of all caves on Earth. The reason for this abundance is the facts that limestone is so common and the slowness of the solution process. If it was faster, the lifespan of limestone caves would be much shorter and their number much lower.
right Speleothems in Hall of the Mountain Kings, Ogof Craig a Ffynnon , South Wales Limestone caves are often adorned with calcium carbonate formations produced through slow precipitation, including the most common and well-known stalactites and stalagmites. These secondary mineral deposits in caves are called speleothems. The world's most spectacularly decorated cave is generally regarded to be Lechuguilla Cave ( New Mexico, USA).
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