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Karst

earth science Maturity 11-13 Next article →

Karst is a unique type of landscape shaped by the dissolution of soluble rocks.

KarstterrainUSGS
KarstterrainUSGS

This topography forms when rocks like limestone or dolomite dissolve in water. It is defined by specific surface features and complex underground drainage systems. These systems include sinkholes, caves, and large basins known as poljes. Because water moves through the ground rather than across it, surface water is often limited. Many karst regions have very few rivers or lakes on the surface.

Causse de Sauveterre doline
Causse de Sauveterre doline

Instead, the water travels through hidden paths deep beneath the earth.

The formation of karst relies on a specific chemical process. It begins when rain falls through the atmosphere and picks up carbon dioxide. This gas dissolves in the water to create a weak carbonic acid. As this acidic rain reaches the ground, it may pass through soil. Soil respiration provides even more carbon dioxide to the water. When this solution hits the bedrock, it reacts with the calcium carbonate in the rock. This reaction dissolves the stone, slowly enlarging cracks into tunnels.

karst Dent-de-Crolle-8
karst Dent-de-Crolle-8

In rare cases, oxidation can also play a role. If oxygen-rich water reaches sulfide-rich systems, it can form sulfuric acid. This stronger acid causes even more rapid erosion of the limestone.

Karst landscapes display many different types of features. On the surface, you might find small solution flutes or limestone pavements. These pavements consist of flat rocks called clints and grikes. Medium-sized features include sinkholes, also called cenotes, and vertical shafts. Large-scale features include massive karst valleys and poljes. In tropical regions, the terrain can look very different. This is called kegelkarst, which features many cone-like hills. These hills are often called mogotes or cockpits.

87340-Li-River (29881879337)
87340-Li-River (29881879337)

Some karst is even hidden beneath layers of insoluble rock like sandstone. This is known as interstratal karst.

The study of these landscapes has a rich history. The term "karst" was borrowed from German in the late 19th century. It describes features found in the Dinaric Alps. This mountain range stretches from Italy across the Balkan peninsula to North Macedonia. In 1689, Johann Weikhard von Valvasor introduced the concept to European scholars. He described how rivers in Slovenia could flow entirely underground. Later, Jovan Cvijić became the "father of karst geomorphology." He published important work in 1893 about landforms like karren and dolines.

Carbonate-outcrops world
Carbonate-outcrops world

He even proposed a model for how these landscapes develop over time.

Understanding karst is vital for several scientific fields. In petroleum geology, scientists study paleokarst, which is fossil karst buried in rock layers. This is important because carbonate rocks host about 50% of the world's hydrocarbon reserves. Much of this fuel is found in porous karst systems. Karst hydrology is also a specific discipline that emerged in the mid-20th century. This field studies how water moves through karst aquifers. These aquifers act like large underground plumbing systems. They consist of open conduits that allow water to flow like underground streams.

MammothCaveNPS
MammothCaveNPS

Karst environments also create unique biological settings. Because the terrain is difficult for humans to travel through, ecosystems often remain undisturbed. The soil in these areas typically has a high pH. This specific chemistry encourages the growth of unusual plant species. You might find unique orchids, palms, and mangroves in these regions. However, some karst types can be dangerous. Salt karst, or halite karst, forms when salt dissolves underground. This can lead to surface collapses that present a geo-hazard.

Puerto Princesa Underground River
Puerto Princesa Underground River

Finally, karst is distinct from pseudokarst. Pseudokarsts look like karst but are formed by different processes. For example, lava caves and granite tors are examples of pseudokarst. They may have similar shapes, but they do not come from chemical dissolution of carbonate rock. Understanding the difference helps geologists correctly identify the history of a landscape. Whether it is a seasonal lake called a turlough in Ireland or a massive cave in the USA, karst shows how water and rock interact over millions of years.

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🖼️ Images & Media (15)
File:Zadar (HR), Krupa-Canyon -- 2022 -- 0003.jpg
Zadar (HR), Krupa-Canyon -- 2022 -- 0003.jpg
File:87340-Li-River (29881879337).jpg
87340-Li-River (29881879337).jpg
File:Paisatge càrstic, 2.jpg
Paisatge càrstic, 2.jpg
File:Carbonate-outcrops world.jpg
Carbonate-outcrops world.jpg
File:Causse de Sauveterre doline.jpg
Causse de Sauveterre doline.jpg
File:Limestone Eocene deposit at Sinj Stari grad - Dalmatia - Croatia IMG 20210820 083857.jpg
Limestone Eocene deposit at Sinj Stari...
File:Kostivere karst area.jpg
Kostivere karst area.jpg
File:karst Dent-de-Crolle-8.jpg
karst Dent-de-Crolle-8.jpg
File:Rubaksa tufa plug.jpg
Rubaksa tufa plug.jpg
File:KarstterrainUSGS.jpg
KarstterrainUSGS.jpg
File:Puerto Princesa Underground River.jpg
Puerto Princesa Underground River.jpg
File:MammothCaveNPS.jpg
MammothCaveNPS.jpg

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