Limestone mountains are most easily destroyed. Limestones are riddled with many cracks, through which rainwater seeps easily. It eats away at soft limestone. Over time, narrow cracks turn into cracks, and cracks into corridors and tunnels. This is how caves arise. They can reach tens or even hundreds of kilometers in length. The longest cave in length (74 km) is Mammoth Cave in the USA, the deepest (1350 m) is Pierre-Saint-Martin Cave in France. There are many caves in the Ural Mountains in Russia, the most famous of which is Kungurskaya.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.