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Roger Weller, geology instructor
by Elsbeth Chavira
Caliche by definition is: A mineral
deposit rich in sodium nitrate occurring naturally in Chile, Peru, and the
southwest United States, and used as fertilizer, in explosives, and as a raw
material for manufacturing nitric acid. Soil in these arid and semiarid regions
have layers of caliche on ounder the surface. The layer can be white or light
colored and can vary in thickness between a few inches to a few feet.
Hayden Butte in Tempe (Arizona State University)
Caliche, also known as hardpan or duricrust, can make digging incredibly difficult. It acts as a natural cement, binding together organic materials. It can be made up of silt, gravel, sand and clay cemented by calcium carbonate, sodium chloride, and other soluble minerals.
Depending on what impurities are present the color of caliche varies. It can range from white, cream, light pink and reddish brown. In the picture below you can see there is both white and pinkish colors through the thick caliche layer.
South Mountain in Phoenix (Arizona State University)
Caliche is a sedimentary rock that can be formed a few different ways. It is generally formed when topsoil losses mineral and organic solutes, a process also known as leaching. At approximately 3-10 feet under the topsoil the minerals accumulates in the next layer of soil. Caliche layers form of less-soluble minerals, after all carbonates have leached from the soil in arid regions. In semiarid regions the caliche consists of carbonates. The calcium carbonate deposits slowly accumulate to form small grains, then clumps, until it forms a thick layer.
When it rains in more arid regions the rain water sinks into the ground rather quickly. The surface of the ground dries, while the rain water underneath rises. Dissolved minerals from the lower layers is carried up by the moving water. This process generally forms a thinner layer of caliche.
Plants can also play a part in the formation of caliche. Water is necessary for the growth of plants. When the roots take in the water they leave behind calcium carbonate.
Caliche can make It very difficult environment for a plant to live. This natural concrete can make it impossible for the plant roots to penetrate it, which can limit the nutrients and water needed to sustain life. Water can not drain properly, and keeping plants from getting enough oxygen. When the water is not able to drain correctly it also allows salt to build up on the top soil and is not good for plant growth.
Caliche layer photo taken in Lea County, New Mexico (photo by Cheryl Kent)
While caliche causes problems in agriculture it does its used for other purposes. It is used worldwide in the construction industry. The chemical composition in caliche meets requirements and is used as a principal raw material in Portland cement. There are caliche reserves in Llano Estacado in Texas that used the caliche to manufacture Portland cement.
It can also be used in the construction of roads. Caliche can be used as a base or as the surface material for a road. It is used most often as a base when it is local, because it is an inexpensive material. Caliche is one of the most used materials in road construction in South Africa.
(Whittlesey Landscape Supplies)
In dry, arid regions there are layers of Caliche under the topsoil. This is made up of soil particles being cemented together by calcium carbonate. Though caliche can be a annoyance to farmers and gardeners it has also proved to be a useful construction material.