Caves are mainly formed by water erosion on soluble rocks such as calcite or limestone, creating underground cavities that can develop into vast underground networks over time.
Beneath our feet, a whole lot of interesting things are happening, and the formation of caves starts precisely with specific geological phenomena. Often, it begins with a layer of limestone or other rocks that are easily attacked by water. Over time, this soluble rock gradually dissolves when in contact with water charged with carbon dioxide, progressively creating underground voids. Other times, it starts with a lava flow: molten lava flows, cools on the surface, but retains a liquid core that eventually drains out, leaving behind a sort of natural tunnel. Your ground also shifts: when there are faults or fractures, water easily seeps through these cracks, accelerating the dissolution of rocks and the creation of even larger cavities. In the end, a simple crack can slowly evolve and become an impressive cave.
Limestone caves mainly result from the interaction between water and limestone, which is rich in calcium carbonate. When rain passes through the atmosphere and the soil, it absorbs some carbon dioxide (CO₂), forming a slightly acidic solution called carbonic acid. This slight acidity gradually suffices to dissolve limestone, leading to a slow but effective chemical reaction. Over time, this dissolution creates underground voids: caves. The amount of water, its acidity, and its duration of action directly influence the size and depth of these underground cavities. And it is this same chemical process that builds, drop by drop, the famous stalactites and stalagmites inside the caves.
Physical erosion is the work done by water as it scrapes, scrapes again and again against rock walls. Basically, water often transports rock debris, sand, or even small stones. These particles act like sandpaper on the rock, and this is called abrasion. Over time, this wear slowly but surely hollows out the walls, forming cavities that will grow and evolve into caves. This process particularly affects soft or crumbly rocks that do not withstand this constant abrasive attack well. In some extreme cases, underground rivers can entirely sculpt vast networks of galleries through this continuous mechanical erosion.
Volcanic caves are not sculpted by water, but mostly originate from lava flows. When a flow descends the slopes of a volcano, its outer layer cools quickly and solidifies into crust, while the interior retains its heat, forming a sort of glowing river. After a while, the lava stops flowing, leaving behind an empty tunnel. This phenomenon gives rise to what is called a lava tunnel, creating caves that can vary enormously in size, with some stretching for several kilometers. Other volcanic caves are formed directly by the emission of burning gases during an eruption, creating smaller cavities formed by these bubbles trapped in the cooling rock. These caves offer a unique universe, very distinct from classical caves sculpted by water, and often quite visually impressive.
The climate plays a huge role in the formation of caves. The more it rains, the more water seeps easily into the ground, bringing with it natural acids that gradually erode the limestone. A humid and warm climate therefore seriously accelerates the appearance of caves, while a dry area significantly slows down the process. In the mountains, for example, the freeze-thaw cycles allow water to carve more quickly by continuously widening existing cracks. Vegetation also has its role: the more abundant it is, the more organic acids it produces that can dissolve certain rocks. In contrast, in desert regions, the formation of caves becomes rare and often very slow.
Some caves house unique forms of life adapted to complete darkness, known as troglobitic species. These include, in particular, blind fish or unpigmented insects.
Some caves have their own microclimate, with almost constant temperatures throughout the year, generally ranging from 10 to 15 degrees Celsius, regardless of the outside weather.
There are underwater caves called cenotes, particularly numerous in Mexico, which once served as sacred places and sources of freshwater for ancient civilizations such as the Mayans.
Here is the translation: "Tasctites hang down from the ceiling, while stalagmites rise up from the ground. A little mnemonic trick: stalacTites with a 'T' come down from the ceiling, while stalagMites with an 'M' rise up from the ground!"
Various animals have adapted to the dark, humid environment of caves, such as bats, troglobitic amphibians (exclusively adapted to underground life), certain albino insects, and specialized microscopic organisms living in subterranean environments.
No. Some caves are difficult to access, dangerous, or protected in order to preserve their fragile ecosystems or rare geological formations. Exploration is therefore regulated, and it is important to engage in it responsibly, usually accompanied by specialists.
In reality, the words 'grotto' and 'cavern' can be used interchangeably in everyday life. However, typically, the term 'cavern' refers to a large cave, particularly spacious, while 'grotto' is a more general term referring to any natural underground cavity.
Yes, caves exist on all continents and in various climates; however, they are more numerous in regions with limestone or volcanic substrates that are conducive to their formation through chemical dissolution or lava flow.
The formation of a cave varies significantly depending on its type and environmental conditions, but in general, it takes thousands or even millions of years. Limestone caves, for example, result from a slow process of chemical erosion over very long periods.
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