Tufa 

Tufa towers at Mono Lake, California.
Tufa forming the Trona Pinnacles, California.
This article is about the geological formation. For the Xianbei clan with the family name Tufa during China's Sixteen Kingdoms period, see Southern Liang.
Not to be confused with tuff, a type of volcanic rock.

Tufa is the name for a form of calcite rock.

Tufa is a calcium carbonate (CaCO3) deposit that forms by chemical precipitation from bodies of water with a high dissolved calcium content. Tufa is not to be confused with tuff, which is volcanic.

Tufa deposition occurs in seven known ways:

  1. Mechanical precipitation by wave action against the shore. This form of tufa can be useful for identifying the shoreline of extinct lakes (for example in the Lake Lahontan region).
  2. Precipitation from supersaturated hot spring water entering cooler lake water.
  3. Precipitation in lake bottom sediments which are fed by hot springs from below.
  4. Precipitation from calcium-bearing spring water flowing into an alkaline lake.
  5. Precipitation throughout a lake as the lake water evaporates, leaving the lake supersaturated in calcium.
  6. Through the agency of algae. Microbial influence is often vital to tufa precipitation and may be involved in the other methods listed.
  7. Precipitation from cold water springs (for example in the foothills of the Rocky Mountains near Hinton, Alberta).

Tufa is common in many parts of the world. There are some prominent towers of tufa at Mono Lake and Trona Pinnacles in California, USA, formed by the fourth method mentioned above whilst submerged and subsequently exposed by falling water levels. Tufa is also common in Armenia and Great Britain.

Practical use

Tufa is today occasionally shaped into a planter. Its porous consistency makes tufa ideal for alpine gardens. A concrete mixture called hypertufa is used for similar purposes.

See also

External links

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