California: Mono Lake
Mono Lake is a saline soda lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in an endorheic basin. The lack of an outlet causes high levels of salts to accumulate in the lake. These salts also make the lake water alkaline. This desert lake has an unusually productive ecosystem based on brine shrimp that thrive in its waters, and provides critical habitat for two million annual migratory birds that feed on the shrimp and alkali flies. Historically, the native Kutzadika'a people derived nutrition from the Ephydra hians pupae, which live in the shallow waters around the edge of the lake. Many columns of limestone rise above the surface of Mono Lake. These limestone towers consist primarily of calcium carbonate minerals such as calcite (CaCO3). This type of limestone rock is referred to as tufa, which is a term used for limestone that forms in low to moderate temperatures. Description of the Mono Lake tufa dates back to the 1880s, when Edward S. Dana and Israel C. Russell made the first systematic descriptions of the Mono Lake tufa. The tufa occurs as "modern" tufa towers. However, there are tufa sections from old shorelines, when the lake levels were higher. These pioneering works in tufa morphology are still referred to by researchers today and were confirmed by James R. Dunn in 1953. The tufa types can roughly be divided into three main categories based on morphology: 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 These tufa types vary interchangeably both between individual tufa towers but also within individual tufa towers. There can be multiple transitions between tufa morphologies within a single tufa tower. Rusell (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 CaO and CO2. However, they also contain minor constituents of MgO (~2 wt%), Fe/Al-oxides (.25-1.29 wt%), and PO5 (0.3 wt%).
Mono Lake is a saline soda lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in an endorheic basin. The lack of an outlet causes high levels of salts to accumulate in the lake. These salts also make the lake water alkaline. This desert lake has an unusually productive ecosystem based on brine shrimp that thrive in its waters, and provides critical habitat for two million annual migratory birds that feed on the shrimp and alkali flies. Historically, the native Kutzadika'a people derived nutrition from the Ephydra hians pupae, which live in the shallow waters around the edge of the lake. Many columns of limestone rise above the surface of Mono Lake. These limestone towers consist primarily of calcium carbonate minerals such as calcite (CaCO3). This type of limestone rock is referred to as tufa, which is a term used for limestone that forms in low to moderate temperatures. Description of the Mono Lake tufa dates back to the 1880s, when Edward S. Dana and Israel C. Russell made the first systematic descriptions of the Mono Lake tufa. The tufa occurs as "modern" tufa towers. However, there are tufa sections from old shorelines, when the lake levels were higher. These pioneering works in tufa morphology are still referred to by researchers today and were confirmed by James R. Dunn in 1953. The tufa types can roughly be divided into three main categories based on morphology: 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 These tufa types vary interchangeably both between individual tufa towers but also within individual tufa towers. There can be multiple transitions between tufa morphologies within a single tufa tower. Rusell (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 CaO and CO2. However, they also contain minor constituents of MgO (~2 wt%), Fe/Al-oxides (.25-1.29 wt%), and PO5 (0.3 wt%).