Mike and I decided to camp on a Mainsail Forest road near Mono Lake and surrounded by mountain ranges,. Mono Lake looked like it was drying up, but still beautiful. The lake has no outlet; water entering the lake can only evaporate away. The water that evaporates leaves behind salts and other chemicals, so like Great Salt Lake, Mono Lake is saltier than the ocean, and its salinity varies with its water level.
With no outlet to the ocean, salt in Mono Lake builds up. Over time, so much has accumulated that white tufa columns – made of limestone, but aided in growth by the water's salinity – jut through its surface and line its banks. The knobby spires can reach a dozen feet into the air.
Mono Lake Basin was formed by the same geologic processes that shaped the Nevada and Eastern Sierra landscape over the past several million years. Extension, or pulling apart, of the Earth's crust has created north/south trending mountain ranges flanked by deep, long valleys.
The lake was nearly depleted by Southern California water diversions almost a century ago and is nothing but salt flats today. The 1994 regulation at Mono Lake established caps on how much Los Angeles can draw from the feeder creeks based on how high the lake is.
The Sierra Nevada has been glaciated repeatedly over the past three million years or so. Geologists recognize at least 11 episodes of ice advance. The most recent advance, called the Matthes glaciation in the Sierra Nevada, occurred during the Little Ice Age, between about 1350 C.E. and 1850 C.E.
Moraines are giant piles of loose sand, cobbles, and boulders that are deposited beneath and around the edges of glaciers. Geologists map moraines and their complex ridges in order to understand the various glacial periods that formed the landscapes we see in the Sierra Nevada and elsewhere. The largest moraines in the Mono Basin, like those around the Grant Lake outlet, Bloody Canyon, and Lee Vining Canyon, were mostly formed during the Tahoe glaciation, which peaked about 50,000 years ago, and the Tioga glaciation, which peaked around 20,000 years ago. At those times, ice would have completely filled the canyons and spilled out into the Mono Basin. A much larger Mono Lake would have hosted icebergs calving off these enormous ice fronts.
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