Geology And Geophysics

How Stalagmites Form

Jose Juan Gutierrez's image for:
"How Stalagmites Form"
Image by: 

Stalagmites are formed by dripping water coming out from the fractures on the ceiling of a cave.  The dripping water contains mineralized solutions and carbon dioxide which build up on the floor of a cave, forming a stalagmite. Stalagmites are known as speleothems which are formations in a cave.  Stalagmites grow up from cave floors. The formation of stalagmites may take from a few hundred years to up to one million years.

How stalagmites form:

When rainwater seeps through the fractures in rock, it gathers carbon dioxide and minerals from limestone which creates carbonic acid. The dissolved substance is carried through the openings of the ceiling of a cave, and when the water is exposed to the air inside the cave, it releases the carbon dioxide, and calcite is deposited in the walls, ceilings and floors of the cave.  The constant dripping of water produces stalactites on the ceiling or stalagmites on the floor of a cave.

The water dripping at the end of a stalactite descends to the floor of a cave and deposits calcite, forming a cone-like shape stalagmite. Most of the time, stalagmites and stalactites get formed in pairs, creating one big column. The color of stalagmites and stalactites is determined by the mineral content, as well as the acids from the surface vegetation.  These elements add the orange, red and black shades to speleothems.

After hundreds or perhaps millions of years, the single drops of water containing dissolved calcite deposit the mineral, forming a stalagmite on the floor of a cave. A stalagmite can grow anywhere between ¼ of an inch to one inch every one hundred years.  If another speleothems (stalactite) which forms on the ceiling of a cave and a stalagmite grow together, they can form a column. Typically, stalagmites and stalactites in caves are composed of calcite, a mineral found in sedimentary rocks. Calcite is made of calcium and carbonate (CaCO3); however, stalagmites and stalactites can also be formed less frequently by aragonite and in rare occasions by gypsum.

Speleothems take various shapes, from tall thin columns to ornate multitier towers, depending on the rate at which calcite crystals form.  The rate of calcite crystal growth is determined by the outside temperature and the amount of rainfall. Temperature influences the rate at which plant and animals decay which determines the quantity of carbon dioxide in the soil.  Speleothem shape is determined by the way in which water gets inside, ceiling height, cave atmosphere and the path in which water flows inside the cave.

Stalactites and stalagmites acquire a variety of shapes and colors that each of them represents a unique appearance. Stalactites and stalagmites are considered natural heritage objects and for this reason are protected by the law in many countries. According to, the tallest stalagmite in the world measures 62.2 meters (204 feet) high and is situated in Cueva Martin Infierno, Cuba.

More about this author: Jose Juan Gutierrez

From Around the Web

  • InfoBoxCallToAction ActionArrow
  • InfoBoxCallToAction ActionArrow