This pressure can force rocks up and out between the cracks. If at these elevations there are inclines, gravity plays a part in moving these angular wedged blocks downslope. The farther rocks move, the smaller they become and the more rounded they become. Hydration - Chemical reaction with water. Minerals can dissolve in water like halite and calcite.
Caves form in limestone which is the sedimentary rock made of the mineral calcite.
Carbonic acid helps dissolve minerals. Clays are stable under conditions at the Earth's surface Feldspars and clays are similar in composition. Feldspar readily alters to clay when in contact with acid and water. The order in which silicate minerals weather. Minerals which form at lower temperatures and pressures are most stable.