The Andes are a range of fold mountains formed about 65 million years ago.
It is the longest range of fold mountains in the world, at 7,000 km, and extends the length of South America, through seven countries, such as Argentina, Bolivia and Chile.
The Andes are about 300 km in width and have an average height of 4,000 m.
Uses of Fold Mountains
Farming
In Bolivia, many subsistence farmers grow a variety of crops on steep slopes, including potatoes, which are their main source of food.
The use of terraces creates areas of flat land on the slopes. The flat areas retain water in areas that receive little, and limit the downward movement of soils in areas where the soils are already thin.
Most crops are grown in the lower valleys, and a patchwork of fields can be seen, indicating the range of crops grown.
Some cash crops are also produced, such as soybeans, rice and cotton.
Llamas
For hundreds of years they have been used as pack animals, carrying materials for irrigation and buildings into inhospitable and inaccessible areas.
The ancient settlement of Machu Picchu relied on llamas to transport materials and goods due to its remote location.
They can carry over 25% of their body weight (125-200kg).
The mining industry often relies on them as a form of transport.
Today, male llamas are still used for this. The females are used for meat and milk, and their wool is used in clothes and rugs.
Mining
The Andes has a range of important minerals and Andean countries rank in the top ten for tin (Peru and Bolivia), nickel (Colombia), silver (Peru and Chile) and gold (Peru)
More than half of Peru's exports are from mining.
The Yanacocha gold mine is the largest gold mine in the world, and is a joint mining venture between a Peruvian mining company and a US based one (with a 51% share).
It is an open pit and the gold-bearing rock is loosened by daily dynamite blasts.
The rock is then sprayed with cyanide and the gold is extracted from the solution.
This has lead to contamination of water supplies.
The nearby town of Cajamarca has grown from 30,000 inhabitants (when the mine began) to 240,000 in 2005 - bringing an alternate source of jobs.
However, this growth also brings many problems, including a lack of services and an increased crime rate.
Hydroelectric Power
The steep slopes and narrow valleys are an advantage for hydroelectric power, as they can be more easily dammed and the relief encourages the rapid fall of water to ensure the generation of electricity.
The melting snow in the spring increases the supply of water, but the variation throughout the year is a disadvantage.
The Yuncan project dams the Paucartambo and Huachon rivers in north-east Peru, and the El Platinal project, which was predicted to start construction in 2009 will dam the Cañete river and will be the second largest in Peru.
Tourism
There are natural attractions like mountain peaks, volcanoes, glaciers and lakes.
Some tourist attractions show how people settled in these inhospitable areas, such as the remains of settlements built by the Incas, like Machu Picchu.
The Inca Trail combines both. It is 45 km long. But, it only allows 200 trekkers each day, and is closed every February for cleaning, as overuse has led to erosion.
Subsistence: Farming to provide food and other resources for the farmer's own family. Terraces: Steps cut into hillsides to create areas of flat land. Irrigation: Artificial watering of the land. Hydroelectric Power: The use of flowing water to turn turbines and generate electricity.