Granite is a plutonic rock created by hardening magma deep underground. In this way, rocks formed under high temperature and pressure conditions deep underground undergo ‘weathering’ where the temperature and pressure decrease and are easily destroyed when they rise near the surface. In particular, weathering occurs actively when rocks come into contact with moisture underground. This is a type of chemical weathering (a phenomenon in which the bonds of minerals that make up rocks break apart) and is called deep weathering (or chemical deep weathering) because it occurs underground.
When deep weathering is accelerated in this way, hard rocks are formed. It is so weak that it can be easily broken even by the force of a human hand, and the material created as a result is called saprolite. However, when granite that has received little or no weathering is exposed above the ground, it does not undergo further deep weathering due to its short contact time with moisture, forming large stone mountains. In other words, after deep weathering, Yonghwasan Mountain was exposed to the surface as a large dome-shaped rock mass with few cracks after the weathered and weakened material (saprolite) was washed away, forming the current rocky mountain.