Here's why:
* Solubility: Limestone is primarily composed of calcium carbonate, which is soluble in acidic water.
* Carbonic Acid: Rainwater absorbs carbon dioxide from the atmosphere, forming weak carbonic acid. This acid reacts with limestone, dissolving it over time.
* Cave Formation: As the acidic water seeps through cracks and fissures in the limestone, it gradually enlarges them, forming caves and caverns.
While limestone is the most common, other rocks can also form caves:
* Gypsum: Gypsum is another soluble rock that can create caves, often in arid climates.
* Salt: Salt caves are less common but can form in areas with large salt deposits.
* Volcanic Rock: Lava tubes, formed by flowing lava, can create caves in volcanic areas.
However, limestone is the dominant rock type responsible for the vast majority of caves and caverns found around the world.
