At over 700,000 years of age, Mono Lake is one of the oldest lakes in North America. It is the remnant of a large Ice Age lake that at one point filled and even overflowed the Mono Basin. This Ice Age lake covered 338 square miles and reached a depth of about 900 feet. Today, fed only by melting snow and underwater springs, the lake covers about 60 square miles, 13 miles east-west by 8 miles north-south.

The Mono Basin has been shaped over millions of years by faulting and volcanic activity. Today, it is a dry sagebrush desert with volcanic hills rising to its north, east and south and the awesome Sierra Nevada Range rising steeply to its west. For the last three to four million years the western floor of the basin has been tilting and slipping downwards while the Sierra has been rising. At the same time "its southern and northern margins tilted slowly towards its center, forming a bathtub like basin that filled with water to form Mono Lake. All of this has produced the contrast of a desert lake bordered by high, forested, stream-riven mountain peaks. Positioned as it is in a basin, Mono Lake now has no outlet. Salts and minerals wash into the lake from Eastern Sierran streams and the water never leaves the basin. Freshwater evaporating from the lake each year has left the salts behind where they concentrate the way they do in the Great Salt Lake. Mono Lake's water is now about two and a half times as salty and eighty times as alkaline as seawater. This gives a slippery or soapy feel to the water which Mark Twain, during

Mono Lake's most notable features are probably its peculiar tufa formations. These bizarre white rock formations are formed when calcium-rich fresh spring water wells up through the alkaline lake water, which is rich in carbonates. The calcium and carbonate combine, precipitating out as limestone. Over many years the hardened minerals pile up inch by inch around the mouth of the spring, forming strangely beautiful towers, spires, knobs and minarets. They are, in effect petrified springs. "This tufa-forming reaction happens only in the lake itself. As the lake level drops and exposes the tufa towers, they cease to grow. As Mono Lake's level dropped through natural evaporation and the diversion of it's freshwater sources to provide drinking water for the Los Angeles area, the lake bed's tufa formations were gradually exposed to view.

The best place to see and wander through these fantastic natural sculptures is in the South Tufa Area where you will find a veritable city of tufa towers, rising both onshore and in the water. The formations in this area are estimated to be between 200 and 900 years old. A boardwalk and pathways allow visitors to explore these tufa towers along the lake's shoreline and its bordering marshes. "Far older tufa towers, some of them as much as 13,000 years old, can still be found high above the current lake, along Mono's ancient shore. Tufa is found in other alkaline bodies of water, but the variety and quantity of Mono's towers is unique. While the surface of Mono Basin is placid, there is a lot of activity underground. The Basin has a long history of vulcanism. Black Point, on the lake's northern perimeter, was once an underwater volcano. The volcanic hills that mark the north and east boundaries of the basin date back some 11 million years. The Mono Craters to the south of the lake, with their dove-colored slopes of ash and pumice are considered to be the youngest mountain range in North America because they began forming less than 60,000 years ago.

Panum, the northernmost of these craters, erupted only 600 years ago. There is a hiking trail that climbs up and around its plug dome. Volcanologists rate these mountains at the top of the list of continental American volcanoes most likely to blow any day. Mono Lake's islands are also volcanic and only popped up recently, geologically speaking. Paoha Island is thought to be only about 200 years old. Hot springs and steam vents in the basin show that volcanic activity is still present and seismic records indicate that these newborn mountains have not yet finished growing.

Mono Lake has been referred to as a "dead sea" but it actually abounds with life. No fish can live in the concentrated minerals and salts of the lake, but brine shrimp and brine flies thrive in astronomical numbers. "Mono" is the Yokut Indian word for "brine fly". The shrimp and flies feed on the microscopic, one-celled algae that bloom in the winter, turning the lake pea soup green. In turn the shrimp and flies provide food for thousands of migratory birds (more than eighty species) that visit the lake each spring and summer. With Paoha Island providing isolation from predators, the Mono Basin has become one of the world's most prolific breeding grounds for California gulls, eared grebes, snowy plovers and Wilson's phalaropes. About 50,000 adult California gulls fly to Mono Lake from the coast each spring to nest. Approximately 90% of the California population of this species is born at Mono Lake. Mark Twain noted "the peculiarity of a sky full of seagulls so far from the sea." Ospreys, great horned owls, and violet-green swallows also sometimes nest in the tufa formations.

Mono Lake's level began dropping in 1941 when the Los Angeles Department of Water and Power diverted four of the five major streams that fed the lake in order to slake the thirst of southern California. As a result, the lake's level dropped an average of 18 inches per year, a total drop of about 45 feet, and its water doubled in salinity, from about 5 to 10 percent. The shoreline marshes and stream habitats vital to wildlife began to disappear and the breeding grounds were threatened when the falling water levels turned the islands into a peninsula open to predators. Wind-blown alkali dust also had an adverse effect on Mono Basin air quality. All of these concerns led citizen groups like the Mono Lake Committee and the National Audubon Society to begin a legal effort to protect Mono Lake. Before long Mono Lake was "at the center of one of the hardest-fought environmental wars of the century, a preeminent political hot potato pitting Los Angeles water consumers against lovers of the land and landowners in the eastern Sierra Nevada. On September 28, 1994, after 16 years of court battles, research and formal hearings, the State Water Resources Control Board issued an order to protect Mono Lake and its tributary streams. The order aimed to raise the lake level by 17 feet over 20 years. So now the creeks are running again, and the lake has begun to rise. Stream and waterfowl habitat restoration efforts are underway. Fish have re-inhabited the streams and Bald Eagles have returned to the area.

The Mono Basin seems to affect different people in different ways, but by anyone’s definition it is a peculiar place. Mark Twain referred to Mono Lake as “one of the strangest freaks of Nature found in any land.” He also commented on “the region’s predictable two seasons: the breaking up of one winter and the beginning of the next.” At the time of his visits the lake was commonly referred to as the Dead Sea of California. He described it in the following words: “Mono Lake lies in a lifeless, treeless, hideous desert…. This solemn, silent, sailless sea---this lonely tenant of the loneliest spot on earth---is little graced with the picturesque. It is an unpretending expanse of grayish water, about a hundred miles in circumference, with two islands in its center, mere upheavals of rent and scorched and blistered lava, snowed over with gray banks and drifts of pumice-stone and ashes…”.

John Muir, on the other hand, referred to the Mono Basin as "a country of wonderful contrasts, hot deserts bordered by snow-laden mountains, cinders and ashes scattered on glacier-polished pavement, frost and fire working together in the making of beauty." Add to this the strange and remarkable tufa towers and you have one of the most extraordinary landscapes in California. If you are lucky, at dusk you may catch "a glimpse of the awesome alpenglow, the strange phenomenon of reflected light that bathes the High Sierra with rose and gold long after the suns rays have vanished. "The Mono Basin Scenic Area Visitor Center is a great place to start your visit to this area. The center is located just off Highway 395, north of Lee Vining and includes a variety of exhibits about the natural and human history of the Mono Basin.