Andes

The Andes are a very long line of mountains in South America.

They go from the warm north all the way to the icy south. Some peaks are snowy volcanoes. High, flat land sits between the mountains, and people and llamas live there.

The Andes are a wall of mountains that runs down the whole western edge of South America. They stretch from the continent's northern coast on the Caribbean Sea to its southern tip, about 8,900 kilometers, by Britannica's measure. Seven countries share them: Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile and Argentina.

The Andes are not one single line of peaks. They are many parallel ranges, called cordilleras, with high plateaus and valleys in between. The highest peak is Aconcagua, in Argentina, at 6,959 meters by Britannica's figure, and Britannica calls it the highest point in the Western Hemisphere. No one is sure where the name Andes comes from; it may come from a word for east, or from words meaning copper.

Britannica describes the Andes as a vast series of extremely high plateaus topped by higher peaks, forming an unbroken rampart some 8,900 km long from the southern tip of South America to its Caribbean coast. The system separates a narrow western coastal strip from the rest of the continent. It is commonly divided into the Southern Andes (Fuegian, Patagonian and Chilean cordilleras), the Central Andes, including the Peruvian cordilleras, and the Northern Andes of Ecuador, Colombia and Venezuela, though there is no universal agreement on the boundaries.

Throughout most of the system run two main ranges, the Cordillera Occidental and the Cordillera Oriental; where the eastern range bulges outward it encloses high plateaus such as the Altiplano, shared by Argentina, Chile, Bolivia and Peru. Aconcagua, at 6,959 m, is the highest point in the Western Hemisphere; Britannica places its peak in Argentina, with its western flanks rising from the coastal lowlands of Chile north of Santiago. The origin of the name is uncertain: Quechua anti, east, or anta, copper, or, perhaps more likely, the older Aymara anta, a copper color.

At the bottom of the Andes it can be hot.

The higher you go, the colder it gets. At the very top it is icy and windy. Up high there is a big, flat land with a huge lake.

In the Andes, climbing up is like changing climates. Britannica describes the Peruvian and Ecuadorian Andes: warm and tropical up to about 1,500 meters, mild between about 2,500 and 3,500 meters, where most people live, freezing at night higher up, and polar above about 4,800 meters, with icy winds.

The Altiplano, or high plain, lies between two ranges in Bolivia and Peru. It is about 800 kilometers long and 130 kilometers wide, sits 3,400 to 3,900 meters high, and has no river that flows out to the ocean. Lake Titicaca fills its northern end, and Britannica calls it the highest navigable lake in the world.

Temperature generally rises northward from Tierra del Fuego to the Equator, but altitude, the cold Peru (Humboldt) Current, rainfall and topography create sharp contrasts; hot rainforest or desert can lie a few miles from tundralike puna. In the Peruvian and Ecuadorian Andes, Britannica gives a tropical zone up to about 1,500 m, subtropical to 2,500 m, the most hospitable zone from 2,500 to 3,500 m, cold with nightly frost from 3,500 to 4,500 m, the páramo-type puna with constant subfreezing temperatures from about 4,100 to 4,800 m, and polar conditions above 4,800 m.

The permanent snow line rises from about 790 m at the Strait of Magellan to about 6,100 m at latitude 27° S, then falls to about 4,600 m in Colombia. The Altiplano, some 800 km long and 130 km wide at 3,400 to 3,900 m, is one of the largest interior basins in the world and has no drainage outlet to the ocean; Lake Titicaca, 110 miles (about 177 km) long, fills its north and drains south through the Desaguadero River to Lake Poopó.

Llamas, alpacas and vicuñas live on the high, cold grassland.

The Andean condor is a huge bird that soars over the mountains. Spectacled bears live in the forests. A plant called Queen of the Andes grows a giant flower spike.

Animals of the Andes live at different heights. The South American members of the camel family, the llama, guanaco, alpaca and vicuña, live mostly on the Altiplano, though they can live lower down too. Scientists think the Andean condor can fly as high as about 7,900 meters.

In Peru, UNESCO protects Huascarán National Park in the Cordillera Blanca. There, vicuñas were close to extinction in the 1960s but have since recovered, one of South America's great conservation successes. The park is also home to spectacled bears, pumas, the Andean mountain cat, more than 100 kinds of birds, including the condor and the giant hummingbird, and about 800 kinds of plants. The most famous is the Queen of the Andes, with its huge flower spike.

Britannica notes that what lives where in the Andes depends on altitude, climate, moisture, soil and food, with the permanent snow line as the upper limit. Cats rarely live above about 4,000 m, while white-tailed mice rarely live below it and reach about 5,200 m; the camelids are animals mainly of the Altiplano, and the condor is thought to fly as high as about 7,900 m. South of about 35° S the flora becomes austral, with mid-latitude rainforests of Araucaria, oak, coigue, cypress and larch.

UNESCO's Huascarán National Park (inscribed 1985, 340,000 ha) protects the heart of the Cordillera Blanca, which it calls the world's highest tropical mountain range, with 27 snow-capped peaks above 6,000 m and Peru's highest, Huascarán, at 6,768 m. Páramo and puna grasslands dominate. The vicuña, close to extinction in the 1960s, has recovered; spectacled bear, puma, North Andean deer and the endangered Andean mountain cat live there, with more than 100 bird species and around 800 plant species, among them the endangered Queen of the Andes. UNESCO estimates that as much as a quarter of the Cordillera's glacial ice may have disappeared since the late 1960s.

People have lived in the Andes for thousands of years.

They grow potatoes and corn on steps cut into the hills. They keep llamas and alpacas for wool. Long ago, people built very long roads across the mountains.

People have lived in the Andes for at least 10,000 to 12,000 years. A significant share of people in Peru and Bolivia live above about 3,000 meters. Britannica says shepherds in southern Peru once lived year-round at 5,212 meters, the highest permanent home it records.

Many people in the Andes speak Quechua or Aymara, and many speak Spanish. Farmers grow corn, potatoes and broad beans, often on terraces, steps cut into steep slopes. Herders keep llamas and alpacas, and some still spin wool with drop spindles. Long ago, the Incas and earlier Andean peoples built the Qhapaq Ñan, a network of roads more than 30,000 kilometers long. UNESCO made it a World Heritage Site in 2014.

Britannica dates the oldest human remains in the Andes to 10,000 to 12,000 years ago, though people probably arrived earlier. Oxygen shortage above about 3,650 m demands deep physiological adaptation; the highest permanent residents on record were shepherds in southern Peru at 5,212 m. From Bolivia to Colombia most major cities lie in the Andes, and in Peru and Bolivia a significant share of people live above about 3,050 m. Quechua speakers form the great majority of Peru's highland population, with Aymara speakers around Lake Titicaca; roughly half of Bolivia's population is Aymara- and Quechua-speaking.

Farming is hard: water is scarce, frosts are common and valleys are small, so terraces extend the cropland. Herding of sheep, goats, llamas and alpacas is widespread, and Andean mining is among the most important in the world, with copper in Chile and Peru and tin in Bolivia. UNESCO's Qhapaq Ñan, Andean Road System (2014) recognizes a network of more than 30,000 km, built over centuries and greatest in the 15th century, with four main routes from Cusco, crossing passes above 6,000 m and linking rainforest, valleys, desert and coast. Today a railway crosses the Ticlio Pass at about 4,800 m.