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 eats away at the limestone. This creates an underground hole or cave. 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.