Editing Mono Lake (section)

==Tufa towers==
Many columns of [[limestone]] rise above the surface of Mono Lake. These limestone towers consist primarily of [[calcium]] [[carbonate]] minerals such as [[calcite]] (CaCO<sub>3</sub>). This type of limestone rock is referred to as [[tufa]], which is a term used for limestone that forms in low to moderate temperatures.<ref>{{cite journal|doi=10.1016/S0012-8252(96)00030-X|last1=Ford|first1=T.D.|last2=Pedley|first2=H.M.|year=1996|title=A review of tufa and travertine deposits of the world|journal=Earth-Science Reviews|volume=41|pages=117–175|issue=3–4|bibcode = 1996ESRv...41..117F }}</ref>

===Tufa tower formation===
Mono Lake is a highly alkaline lake, or [[soda lake]]. [[Alkalinity]] is a measure of how many [[Base (chemistry)|bases]] are in a [[Solution (chemistry)|solution]], and how well the solution can neutralize [[acid]]s. [[Carbonate]] (CO<sub>3</sub><sup>2-</sup>) and [[bicarbonate]] (HCO<sub>3</sub><sup>−</sup>) are both bases. Hence, Mono Lake has a very high content of [[Total inorganic carbon|dissolved inorganic carbon]]. Through supply of [[calcium]] ions (Ca<sup>2+</sup>), the water will precipitate [[Calcium carbonate|carbonate-minerals]] such as [[calcite]] (CaCO<sub>3</sub>). Subsurface waters enter the bottom of Mono Lake through small springs. High concentrations of dissolved calcium ions in these subsurface waters cause huge amounts of calcite to precipitate around the spring orifices.<ref name=":72">{{Cite journal|last=Dunn|first=James|date=1953|title=The origin of the deposits of tufa in Mono Lake|journal=Journal of Sedimentary Petrology|volume=23|pages=18–23|doi=10.1306/d4269530-2b26-11d7-8648000102c1865d}}</ref>

The tufa originally formed at the bottom of the lake. It took many decades or even centuries to form the well-recognized tufa towers. When lake levels fell, the tufa towers came to rise above the water surface and stand as the pillars seen today (see [[Mono lake#Lake Level History]] for more information).<ref>{{cite web|url=https://www.monolake.org/learn/aboutmonolake/naturalhistory/tufa/|title=Tufa|date=22 September 2020 |publisher=Mono Lake Committee|access-date=2023-05-29}}</ref>

===Tufa morphology===
[[File:Thinolite sketches.png|thumb|upright=0.8|These are original sketches of thinolite made by Edward S. Dana from his book from 1884: ''Crystallographic Study of the Thinolite of Lake Lahontan''.<ref name=":82">{{cite book|last=Dana|first=ES|year=1884|title=A crystallographic study of the thinolite of Lake Lahontan|number=12|publisher=Government Printing Office}}</ref>]]
Description of the Mono Lake tufa dates back to the 1880s, when [[Edward Salisbury Dana|Edward S. Dana]] and [[Israel Russell|Israel C. Russell]] made the first systematic descriptions of the Mono Lake tufa.<ref name=Russell1889>{{cite book|last=Russell|first=IC|year=1889|chapter=Quaternary history of Mono Valley, California|title=U. S. Geol. Survey 8th Ann. Rept. for 1886-1887|pages=261–394}}</ref><ref name=":82"/> The tufa occurs as "modern" tufa towers. There are tufa sections from old shorelines, when the lake levels were higher. These pioneering works in tufa morphology are referred to by researchers and were confirmed by James R. Dunn in 1953. The tufa types can roughly be divided into three main categories based on morphology:<ref name=":72"/><ref name=Russell1883>{{cite book|last=Russell|first=IC|year=1883|chapter=Sketch of the geological history of Lake Lahontan|title=U. S. Geol. Survey 3rd Ann. Rept. for 1881-1882|pages=189–235}}</ref>

*Lithoid tufa - massive and porous with a rock-like appearance
*Dendritic tufa - branching structures that look similar to small shrubs
*Thinolitic tufa - large well-formed crystals of several centimeters

Through time, many hypotheses were developed regarding the formation of the large [[thinolite]] crystals (also referred to as [[glendonite]]) in thinolitic tufa. It was relatively clear that the thinolites represented a calcite [[pseudomorph]] after some unknown original [[crystal]].<ref name=":82"/> The original crystal was only determined when the mineral [[ikaite]] was discovered in 1963.<ref name=Pauly1963>{{cite journal|last=Pauly|first=H|year=1963|title="Ikaite", a New Mineral from Greenland|journal=Arctic|volume=16|issue=4|pages=263–264|doi=10.14430/arctic3545|doi-access=free}}</ref> Ikaite, or hexahydrated CaCO<sub>3</sub>, is [[Metastability|metastable]] and only crystallizes at near-freezing temperatures. It is also believed that calcite crystallization inhibitors such as [[phosphate]], [[magnesium]], and [[organic carbon]] may aid in the stabilization of ikaite.<ref name=Council1993>{{cite journal|last1=Council|first1=TC|last2=Bennett|first2=PC|year=1993|title=Geochemistry of ikaite formation at Mono Lake, California: Implications for the origin of tufa mounds|journal=Geology|volume=21|issue=11|pages=971–974|doi=10.1130/0091-7613(1993)021<0971:GOIFAM>2.3.CO;2 |bibcode=1993Geo....21..971C }}</ref> When heated, ikaite breaks down and becomes replaced by smaller crystals of calcite.<ref name=Shearman1989>{{cite journal|last1=Shearman|first1=DJ|last2=McGugan|first2=A|last3=Stein|first3=C|last4=Smith|first4=AJ|year=1989|title=Ikaite, CaCO3̇6H2O, precursor of the thinolites in the Quaternary tufas and tufa mounds of the Lahontan and Mono Lake Basins, western United States|journal=Geological Society of America Bulletin|volume=101|issue=7|pages=913–917|doi=10.1130/0016-7606(1989)101<0913:ICOPOT>2.3.CO;2 |bibcode=1989GSAB..101..913S }}</ref><ref name=Swainson2001>{{cite journal|last1=Swainson|first1=IP|last2=Hammond|first2=RP|year=2001|title=Ikaite, CaCO3· 6H2O: Cold comfort for glendonites as paleothermometers|journal=American Mineralogist|volume=86|issue=11–12|pages=1530–1533|doi=10.2138/am-2001-11-1223 |bibcode=2001AmMin..86.1530S |s2cid=101559852 }}</ref> In the Ikka Fjord of [[Greenland]], ikaite was also observed to grow in columns similar to the tufa towers of Mono Lake.<ref name=Buchardt2001>{{cite journal|last1=Buchardt|first1=B|last2=Israelson|first2=C|last3=Seaman|first3=P|last4=Stockmann|first4=G|year=2001|title=Ikaite tufa towers in Ikka Fjord, southwest Greenland: their formation by mixing of seawater and alkaline spring water|journal=Journal of Sedimentary Research|volume=71|issue=1|pages=176–189|doi=10.1306/042800710176|bibcode=2001JSedR..71..176B}}</ref> This has led scientists to believe that thinolitic tufa is an indicator of [[Paleoclimatology|past climates]] in Mono Lake because they reflect very cold temperatures.<ref>{{cite journal|last1=Whiticar|first1=MJ|last2=Suess|first2=E|title=The Cold Carbonate Connection Between Mono Lake, California and the Bransfield Strait, Antarctica|journal=Aquatic Geochemistry|volume=4|pages=429–454|year=1998|issue=3/4 |doi=10.1023/A:1009696617671|s2cid=130488236 }}</ref>

===Tufa chemistry===
Russell (1883) studied the chemical composition of the different tufa types in [[Lake Lahontan]], a large [[Pleistocene]] system of multiple lakes in California, Nevada, and Oregon. Not surprisingly, it was found that the tufas consisted primarily of [[Calcium oxide|CaO]] and [[Carbon dioxide|CO<sub>2</sub>]]. However, they also contain minor constituents of [[Magnesium oxide|MgO]] (~2 wt%), [[Iron oxide|Fe/Al-oxides]] (.25-1.29 wt%), and [[Phosphorus oxide|PO<sub>5</sub>]] (0.3 wt%).{{citation needed|date=May 2023}}