Natural springs form when pressurized aquifer or groundwater flows onto the land surface. Springs may form in various landscapes, including a valley bottom, the side of a hill and in any sort of rock. Springs are classified into different categories, including seepage, artesian and tubular springs.
A seepage spring is a small wet or moist puddle of water where groundwater slowly seeps onto the surface. It is formed when the aquifer water runs downhill and collects in an area of lower elevation. It can also occur in elevated areas where there is an abundance of groundwater. An artesian spring, on the other hand, occurs when groundwater is discharged along faults, joints or fissures in the bedrock, and it may flow on cliffs and valleys.
A tubular spring is part of the karst topography system and is associated with limestone, volcanic lava tubes and caverns. It occurs when rainwater seeps through the ground and dissolves the layers of limestone and dolomite, forming huge cavities and caves through the limestone. When the foundation of these caves collapses, it forms a karst topography, which includes springs, sinkholes and caves. It takes thousands of years to form a tubular spring. The large springs in Southern Minnesota and in Florida are most likely formed by sinkhole activity.