The Tufa Towers of Mono Lake

The Tufa Towers of Mono Lake. Photo Credit: Tim Malabuyo

The rock formations along the shores of Mono Lake are identified as tufa. Mono Lake is a large, shallow saline lake situated in Mono County, California, United States. It is located in the eastern Sierra Nevada Mountains, east of Yosemite National Park and south of Lake Tahoe.

What is Tufa

Tufa is a porous, sedimentary rock composed primarily of calcium carbonate, classified as limestone. It forms through the precipitation of minerals from water in environments such as springs, lakes, or rivers.

The term "tufa" applies specifically to deposits formed in ambient-temperature water, distinguishing it from travertine, which develops in hot springs. At Mono Lake, tufa results from the interaction of calcium-rich freshwater from underground springs with the lake’s alkaline, carbonate-rich water. This chemical reaction produces solid calcium carbonate, which accumulates over time into tower-like structures. These formations develop underwater and become visible when lake levels decrease.

Characteristics of Mono Lake

Mono Lake is among the oldest lakes in North America, with an estimated age exceeding 1 million years. It receives water from rivers and streams descending from the Sierra Nevada, and lacking an outlet, it has accumulated high levels of salts and minerals. The lake’s salinity is approximately 2.5 times that of seawater, and its pH is approximately 9.8, indicating strong alkalinity due to elevated carbonate concentrations.

Mono Lake's "South Tufa" area. Photo: By Nandaro CC

Formation Process of Tufa

Tufa at Mono Lake forms entirely underwater. Calcium-rich freshwater springs emerge from the lakebed, introducing calcium into the carbonate-rich lake water. The resulting chemical reaction produces calcium carbonate (calcite, CaCO3), which precipitates as a solid around the spring. Over decades to centuries, this process constructs tufa towers, some exceeding 30 feet in height. Water diversions in the 20th century reduced the lake’s level, exposing these structures.

Mono Lake's "South Tufa" area. Photo: By Nandaro CC

Significance of the Tufa

The tufa towers of Mono Lake are composed of limestone and shaped by the lake’s unique chemical and geological conditions. They provide evidence of the lake’s long history and environmental changes. Conservation measures have stabilized water levels, ensuring the preservation of these formations.