The name of this lake means Stone Puma, a puma being a mountain lion. Lake Titicaca is indeed a large creature of the mountains. Lying on a vast, high plateau between two arcs of the Andes Mountains, it is the highest lake in the world that is also deep enough to be navigable: Its elevation is just over 12,500 feet (3,812 m) above sea level.
By volume of water Lake Titicaca is the largest lake in South America and the 19th largest in the world. In extent it covers more than 3,000 square miles (8,000 km2), stretches more than 110 miles (177 km) long, lies 50 miles (80 km) cross at its widest point, and reaches a maximum depth of about 1,200 feet (300 m) during the summer in a year of good rainfall.
Lake Titicaca, lying part in southern Peru and part in northern Bolivia, is also both a tropical and a desert lake. It actually remains warm enough to help heat its environment year round; its latitude, about 15°S, makes it comparable to Guatemala (about 15 degrees from the equator in the other direction). The lake loses almost as much water to evaporation each year (more than 90 percent) as it receives from its rivers and the limited rainfall; only ne river flows out of Titicaca and it transports little water away. The lake receives low levels of precipitation ince it lies in the rainshadow of the Andes. (For more on rainshadows, please see chapter 1: Caspian Sea.) Though the vast Amazonian rain forest lies over the Andes’ Eastern Mountains beyond Lake Titicaca, the lake’s rainfall, scant, occurs primarily during its short December to March summer. So the lake is gradually becoming saltier. (When low levels of freshwater enter a lake, natural salts build up as they leach out from the rocks and soil.) Its overall salt level here is about .1 ounce per gallon (800 mg/l).
Lake Titicaca sits on a vast plateau called the Altiplano (or high plain), a broad, long north-south stretch of arid and between the Cordillera Oriental (the Eastern Mountains of the Andes) and the Cordillera Occidental (the Andes’s Western Mountains, which include active Lake Titicaca G 67 volcanoes). The largest salt flat in the world, the Salar de Uyuni, is to its southwest. Its dry shoreline can be seen in the color insert on page C-4. Peaks of the Andes can be seen from Lake Titicaca, and this mountain range is very active tectonically, resulting in frequent earthquakes at Titicaca. These “shudders” regularly damage the roads and
railways the people use to get their farm products to market in the many surrounding towns. Textile manufacturing, mining, and illegal drugs such as heroin are also part of commercial activity here, with indigenous people in the area now trying to achieve more control over the oil and gas resources. Lake Titicaca is home to more than 40 islands, two main kinds of native fish (a catfish and a smaller black-striped fish), trout (which were introduced and altered local ecology for the worse by introducing a fish parasite), and a species of frog that grows to almost one foot (.3 m) long. The lake is so high in altitude and so far from any other cool freshwater environments that its native organisms were probably introduced originally on the feathers and in the wastes of birds who flew to it. It still has relatively few fish compared to most lakes. A narrow ridge separates the lake into two basins, though they are connected by a natural canal called the Strait of Tiquina. Only a small amount of water is exchanged between them. The larger, deeper, northwestern basin is called Lake Grande in Peru and Lake Chucuito in Bolivia and the smaller, southeastern one goes by the name of Lake Pequeno in Peru and Lake Huinaymarca in Bolivia.
Lake Titicaca is of both glacial and tectonic origin. Since the tectonic activity began first chronologically, it shall be discussed first. The activity began with the Andes. The Andes Mountains, near Titicaca (as can be seen in the color insert on page C-3) extend down virtually the entire west coast of South America. Even the Falkland Islands off the continent’s southeastern tip are a continuation of this immense, high mountain range. And the Andes hemselves form a partial arc of an even more extensive planetary feature, called the Ring of Fire. This “ring” is the tectonically active rim of the whole Pacific Ocean. It extends its “geoaction” all the way up the west coast of the United States from California up to southern Alaska, then west to Russia, south through Japan, the Philippines and Indonesia, and all the way to New Zealand. An Earthsized geological phenomenon, the Ring of Fire is noted for its dramatic and often drastically destructive earthquakes and active volcanoes. These “fireworks,” which also build up volcanic mountains around the world, are the result of clashes between the Pacific plate and the various other continental plates that abut it. 68 G Lakes It is not a coincidence that the Andes are near the Peruvian coast here, or that mountains are near the coast anywhere on the Ring of Fire. The Andes of South America are a mighty uplift caused as the Pacific crustal plate collides here with the South American or Nazca plate. Part of the land gets pushed up, or uplifted, and lava also gets blasted out of volcanoes; the result is highlands, volcanic mountains, and other mountains.
The geological action occurs because the land on the oceanic plate gets shoved under the continental plate and toward the mantle and core of the Earth; the phenomenon is called a subduction zone. This kind of slow but steady drama has been going on in western South America for a long time already, and it will continue as far as geologists
can see into the future. The Ring of Fire is not cooling down, here or anywhere. The Andes are still growing. But the process does have stages.