The Andes are the world's longest exposed mountain range, with a length of 4,400 miles (7,000 km), 125 miles (200 km) wide, and an average height of 13,000 ft (4,000 m). In comparison, the world's longest submerged range is the mid-ocean ridge, which is 40,400 miles (65,000 km) long. The Andes are famous as the largest mountain range in South America, extending for most of the west coast of South America. The mountains were formed during the Jurassic and Cretaceous periods, when the Antarctic Plate and the Nazca Plate caused extensive uplifting as they pushed east into the South American Plate.
As the most important mountain range in South America, the Andes are rich both in biodiversity and cultural diversity. People have lived in the mountains for over 10,000 years, and 6,000 years ago developed irrigation techniques they used to grow maize and potatoes. During the 1400s, the Inca Empire developed in the northern Andes, and expanded southwards, terracing parts of the mountains and using them as territories to expand their empire.
One of the most famous sites in the Andes is Machu Picchu, the ruins of an Incan city at 7,874 ft (2,400 m), sometimes called "the Lost City of the Incas." Machu Picchu is one of the only Incan cities that was not discovered by the Spaniards when they conquered the Incan Empire in the early 1500s, hidden in the Andes high above the Amazon Rainforest. This means that it was never plundered or destroyed, unlike most other Inca sites. However, it was forgotten for almost 400 years, only being called to the attention of the western world in 1911 by Hiram Bingham, a lecturer at Yale University. Today, the site receives over 400,000 visitors annually.
The Andes stretch through seven countries: Argentina, Bolivia, Chile, Columbia, Ecuador, Peru, and Venezuela. The tallest peak is Aconcagua, at 22,841 ft (6,962 m), the world's tallest mountain outside of Asia. As the tallest mountain on the continent of South America, it is part of the Seven Summits. Another notable mountain in the Andes is Mount Chimborazo, the spot in the world farthest from the center of the Earth (due to the planet's equatorial bulge). Like many other mountains in the Andes, Chimborazo is a volcano, though it last erupted over 1000 years ago. As a volcanically active region, the Andes are part of the "Ring of Fire" that surrounds the Pacific.