Caves are underground passages and are created through a eroding of chemical, water and pressure. The majority of caves are found in combination areas. Sometimes, water only drips very slowly and gradually ___ at the limestone. This creates an underground hole or ____. Some caves are formed by a hydrogen gas coming from deep below the Earth. Other caves are sea caves. The ___ pound the coastline, ____ weak areas in the rock. in limestone caves, unique features called stalactites and stalagmites can be found.