How Caves Form in Limestone
The technical terms are introduced by capital initials.
Most of the world’s caves are in Limestone.
Caves need three materials: a soluble rock like Limestone or Gypsum, water and Carbon-dioxide (CO2).
Their host limestone also needs to be of appropriate physical structure and raised into hills, then subjected to reasonably consistent precipitation for many tens or hundreds of thousands of years.
Limestone is a sedimentary rock of which the world’s greater proportion was laid down in warm, relatively shallow, seas. The rock was laid in horizontal layers – Beds – separated by Bedding-planes which generally reflect geologically-brief changes in the environment. The suite of beds is known as a Formation, generally named after its “type areaâ€.
Later continental uplift (tectonic processes) raise the formation along with its underlying rocks, usually tilting and folding it to at least some extent in the process. Since most rocks are brittle they cannot take much stress, and limestone beds crack into grids of fine fractures called Joints. The uplift and folding often also causes Faulting – major breaks with the rock mass one side of the Fault Plane being raised, lowered or moved horizontally past that on the opposite side. (Note: Plane – the “Fault Line†sometimes misused as a political metaphor is that of the fault-plane cutting the land surface.)
Now we have the hills, next we need rain-water that has absorbed atmospheric CO2 to create Carbonic Acid (weak, natural soda water in fact!). It may be augmented by acids from the soil, too. This solvent permeates through all those joints, bedding-planes and faults; flowing very, very slowly under considerable pressure applied by its depth, from its sinks on the surface to its springs at the base of the formation. In doing so, it dissolves the limestone (chemical weathering), creating meshes of tiny micro-conduits that over many tens of thousands of years coalesce and capture each other to form cave passages.
Once this happens, the rate of erosion can increase – though still to perhaps only a few millimetres per thousand years under generally temperate climates.
A cave, or a series within a cave system, that still carries its formative stream is called “Activeâ€, and is still being developed.
Surface changes such as the valley floor being lowered by erosion, or down-cutting within the cave by its stream, changes the water’s route and the original, now dried-out, stream-way is called “Fossil†or “Abandonedâ€. Such passages may be filled with silt left by floods as the main flow gradually abandons them; or may become richly decorated with Speleothems – calcite deposits such as stalactites and stalagmites precipitated from ground-water still oozing through the joints in the limestone above the cave. In time such passages may start to break down as there is no stream to dissolve away slabs falling from the roof as permeating ground-water attacks the rock above.
In the end, surface lowering of the landscape as a whole, breaches and destroys the cave. Nothing is permanent in Nature!
Caves in limestone are also parts of Karst Landscape. i.e. a landscape developed by the dissolution of limestone, giving surface features like Dolines, Limestone Pavement, and in the tropics, distinctive hills such as those represented in Chinese Willow-pattern images. ‘Karst’ is from the Slavic word ‘Kras’, the name for its world type-area.
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The above is purely an introduction to a vastly more complex and subtle series of processes, of course, and you need to refer to appropriate text-books on geology and cave studies to learn them.
The scientific study of caves is Speleology – embracing geology, hydrology, Biology, Archaeology and other disciplines.
Simply visiting caves to enjoy them for their scenery and the physical and mental challenges they present, is called Caving, though you can’t study a cave unless you can negotiate its obstacles. The enthusiasts are simply Cavers throughout the English-speaking world – you see “spelunkers†sometimes on ‘Answers’ but it's an old slang word not found in caving literature.
So in summary (mostly that someone added!):
Regions dominated by limestone have many characteristic landforms, including limestone caves, also called solution caves. The caves form as limestone rock is dissolved away over the course of many years. Rain-water absorbs carbon diosxide from the atmosphere and the soil as it seeps through the ground. They react chemically to form carbonic acid, a very weak acid that slowly dissolves the limestone.
The mineral is often redeposited later as stalactites or stalagmites, characteristic formations of a limestone cave, though most of the dissolved calcium carbonate is carried away entirely in the water emerging from the cave's rising (the spring that is its outlet.)
Mammoth Cave is a limestone cave system, located in Kentucky, USA. It is a type of karst landscape, characterized by the dissolution of soluble rocks like limestone, resulting in unique underground formations and passageways.
limestone
Caves usually and mostly forms in sedimentary rocks. Example, Limestone.
In caves, you are most likely to find sedimentary rocks, particularly limestone, which is formed from the accumulation of organic materials and minerals. Limestone is especially prone to chemical weathering, leading to the formation of karst landscapes with features like stalactites and stalagmites. Other types of rocks, such as dolostone and gypsum, may also be present in some cave systems.
Stalagmite. The opposite, growing downwards from the roof, is a "stalactite".
Fallen boulders, calcite formations and sediment! Mammoth Cave is a karst cave; formed within limestone.
Mammoth Cave is a limestone cave system, located in Kentucky, USA. It is a type of karst landscape, characterized by the dissolution of soluble rocks like limestone, resulting in unique underground formations and passageways.
No, not all caves are made of limestone. Caves can be formed in various types of rocks, including granite, sandstone, and volcanic lava flows. Limestone caves are common because limestone is soluble and can be eroded by water to create cave systems, but caves can also form in other types of rocks through different geological processes.
limestone
Limestone
limestone
The rocks found in most caves are typically sedimentary rocks such as limestone, shale, and sandstone. These types of rocks are more susceptible to erosion by water, which is a common process in cave formation. Additionally, sedimentary rocks often contain minerals that are easily dissolved by water, leading to the creation of cave features like stalactites and stalagmites.
Limestone - sedimentary deposition of calcarious marine organisms. Marble - compressed (metamorphosed) limestone.
Rocks or Bats i think
Caves most commonly form in areas with limestone or other soluble rocks that are easily eroded by water. The process of cave formation typically involves the dissolution of rock by acidic groundwater, creating underground voids. Over time, these voids can develop into large cave systems through ongoing erosion and geological processes.
In limestone uplands offering a suitable combination of geology and long-term climate hence hydrology to encourage cave development. Other types of cave occur in other rocks but the vast majority are in limestone.
Most sinkholes form when mildly acidic water dissolves limestone underground, this forms a limestone cave. A sinkhole occurs when the cave collapses.