additionally , underground rivers f

additionally , underground rivers find their way into caves though entrance holes they make the cave bigger through erosion when an underground river exits a cave, it is called a spring apart from the limestone caves, some caves are formed by a hydrogen gas it comes from deep below the earth and rises to the surface the gas dissolves or eats away at the rock and creates a cave other caves are sea caves they are found along coastlines
the waves pound the coastline, eroding weak areas in the rock