Solutional cave

A solutional cave, solution cave, or karst cave is a cave usually formed in a soluble rock like limestone (Calcium carbonate CaCO₃). It is the most frequently occurring type of cave. It can also form in other rocks, including chalk, dolomite, marble, salt beds, and gypsum.^[1]

Gypsum stalactites in a cave formed via sulfuric acid dissolution (Lechuguilla Cave, New Mexico)

Process

Bedrock is dissolved by carbonic acid in rainwater, groundwater, or humic acids from decaying vegetation, that seeps through bedding planes, faults, joints, and the like. Over time, the surface terrain breaks up into clints separated by grikes and punctuated by sinkholes into which streams may disappear, crevices expand as the walls are dissolved to become caves or cave system. These may turn into large caverns or dolines when the roof collapses.^[2]

The portions of a solutional cave that are below the water table or the local level of the groundwater are flooded.^[3]

Limestone caves

Limestone cave Kolbinger Höhle^[4]

The largest and most abundant solutional caves are located in limestone. Limestone caves are often adorned with calcium carbonate formations produced through slow precipitation. These include flowstones, stalactites, stalagmites, helictites, soda straws, calcite rafts, and columns. These secondary mineral deposits in caves are called "speleothems".^[2][5][6]

Carbonic acid dissolution

Limestone dissolves under the action of rainwater and groundwater charged with H₂CO₃ (carbonic acid) and naturally occurring organic acids. The dissolution process produces a distinctive landform known as "karst", characterized by sinkholes and underground drainage. Solutional caves in this landform—topography are often called karst caves.

Sulfuric acid dissolution

Lechuguilla Cave in New Mexico and nearby Carlsbad Caverns are now believed to be examples of another type of solutional cave. They were formed by H₂S (hydrogen sulfide) gas rising from below, where reservoirs of petroleum give off sulfurous fumes. This gas mixes with ground water and forms H₂SO₄ (sulfuric acid). The acid then dissolves the limestone from below, rather than from above, by acidic water percolating to the surface.

Examples

Australia

• Jenolan Caves, New South Wales

Malaysia

• List of caves in Malaysia

Taiwan

• Black Dwarf Cave, Pingtung County

United States

• Jewel Cave National Monument, South Dakota
• Mammoth Cave National Park, Kentucky
• Russell Cave National Monument, Alabama
• Wind Cave National Park, South Dakota
• Oregon Caves National Monument and Preserve, Oregon
• Cumberland Caverns, Tennessee

Vietnam

• Hang Sơn Đoòng, Quảng Bình Province

Germany

• König-Otto-Tropfsteinhöhle