Limestone Landforms & Underground Water Features

Stalactites and Stalagmites

• Stalactites and stalagmites are limestone formations that occur inside caves. Stalactites develop from the ceiling down, and stalagmites form from the floor up. The water inside the cave dissolves limestone on the roof and drips downward. As the water evaporates, the drips harden and build up on one another forming an icicle-shaped stalactite. When water does not evaporate quickly enough, the drop falls to the floor. After hitting the floor the water evaporates, and the limestone residue builds up to form a stalagmite. Eventually, stalagmites and stalactites grow together to form a column.

Swallow Holes and Caves

• A swallow hole is where a crack or gap in the limestone surface allows water from a surface river or creek to flow in. The running water slowly erodes the limestone around the crack to create a large hole. At the same time, the water that goes through the crack erodes limestone below the soil to form a cave. Eventually, the river completely disappears into the swallow hole. This is sometimes called the "mouth" of a cave. The cave is hollowed out and grows larger as the flow of water breaks down the limestone, leaving open spaces. The water works into cracks in the limestone, forming different rooms in the cave or tunnels between rooms.

Limestone Pavement

• Large glacial planes often had a bed of thick limestone beneath them. As the glaciers melted away, and any soil eroded, a large sheet of limestone was exposed. These large sheets of limestone, also known as alvars, are called "limestone pavement" because of their resemblance to a poured concrete pad. They are most common in the northern part of the United Kingdom, Sweden and the French Alps.

Clints and Grykes

• Clints and grykes are a special, above-ground limestone formation that look similar to a checkerboard or tile floor. As rainwater flows over a sheet of limestone pavement, it works into cracks and erodes the limestone at the cracks' edges. The resulting formation is large, generally rectangular, blocks of stone separated by widened cracks. The blocks are called clints and the spaces are called grykes.