Travertine
[2][3] It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot spring or in a limestone cave.
[7][11] Travertine is often defined in a more narrow sense as dense rock, sometimes massive but more commonly banded or with a fibrous internal structure, deposited in hot springs.
Water passing through soil picks up carbon dioxide from plant roots and decaying organic matter.
When this groundwater then emerges into a cave with a lower concentration of CO2, some of the CO2 escapes, allowing calcium carbonate to precipitate and build up stalactites, stalagmites, and other speleothems.
[33] Precipitation may be enhanced by factors leading to a reduction in pCO2, for example increased air-water interactions at waterfalls may be important,[34] as may photosynthesis.
[35] Rarely, travertine may form from highly alkaline water containing dissolved calcium hydroxide (Ca+2 + 2OH−) produced during serpentinization of ultramafic rock.
Likewise, water carbonated by passage through soil will occasionally have circulated to sufficient depths that it is quite warm when it reemerges at the surface.
Water carbonated by volcanic activity will nonetheless tend to have a higher content of dissolved calcium bicarbonate and will generally be more enriched in the heavier 13C isotope.
[40] Tivoli travertine was deposited in a body 20 square kilometers (7.7 sq mi) in area and 60 meters (200 ft) thick along a north-trending fault near the dormant Colli Albani volcano.
Detailed studies of the Tivoli and Guidonia travertine deposits revealed diurnal and annual rhythmic banding and laminae, which have potential use in geochronology.
Cascades of natural lakes formed behind travertine dams can be seen in Pamukkale, Turkey, which is a UNESCO World Heritage Site.
Other places with such cascades include Huanglong in Sichuan Province of China (another UNESCO World Heritage Site), the Mammoth Hot Springs in the United States, Egerszalók in Hungary, Mahallat, Abbass Abad, Atash Kooh, and Badab-e Surt in Iran, Band-i-Amir in Afghanistan, Lagunas de Ruidera, Spain, Hierve el Agua, Oaxaca, Mexico and Semuc Champey, Guatemala.
In Central Europe's last post-glacial palaeoclimatic optimum (Atlantic Period, 8000–5000 BC), huge deposits of tufa formed from karst springs.
[48] Travertine has formed 16 natural dams in a valley in Croatia known as Plitvice Lakes National Park.
Clinging to moss and rocks in the water, the travertine has built up over several millennia to form waterfalls up to 70 m (230 ft) in height.
Turner Falls, the tallest waterfall in Oklahoma, is a 77 feet (23 m) cascade of spring water flowing over a travertine cave.
Travertine Creek flows through a spring-water nature preserve within the boundaries of the Chickasaw National Recreation Area.
[70] The Tivoli quarries supplied the travertine from which Gian Lorenzo Bernini selected material from which to build the colonnade of St. Peter's Square in Rome (colonnato di Piazza S. Pietro) in 1656–1667.
[citation needed] Twentieth century buildings using travertine extensively include the Sacré-Cœur Basilica in Paris, the Getty Center in Los Angeles, California, and Shell-Haus in Berlin.
[80] The Ronald Reagan UCLA Medical Center is clad with over 3 million pounds (about 1360 tonnes) of Ambra Light travertine from the Tivoli quarries.
[81] Architect Ludwig Mies van der Rohe used travertine in several of his major works, including the Toronto-Dominion Centre,[82] S.R.
[87][88] Until the 1980s, Italy had a near-monopoly on the world travertine market; now significant supplies are quarried in Turkey, Mexico, China, Peru, and Spain.
