The Ecuadorian Andes are divided into parallel volcanic cordilleras that form Ecuador's central Andean highlands region. This Sierra natural region contains ten major basins that contain roughly half of Ecuador's population.
The Ecuadorian Andes, part of the Tropical Andes (a climate-delineated region of the greater Andes mountain system of South America), runs through the center of Ecuador, from the border with Colombia in the north to Peru in the south.
The mountain range system is divided into parallel cordilleras that form Ecuador's central Andean highlands region. The cordilleras run in a slightly curved S-shape from north to south. The subduction of the Nazca Plate underneath the South American Plate formed the cordilleras.
The mountain system is a 600 km- (375 mi-) long narrow plateau bordered by two parallel chains containing numerous volcanoes. In addition, several transversal mountain spurs, known as nudos, cut across the plateau.
To the west, the generally lower elevation Cordillera Occidental includes 19 volcanoes. To the east, the generally higher Cordillera Central consists of 20 volcanoes, some of which have permanent snowcaps. A third cordillera has been identified in Ecuador's eastern jungle and named the Cordillera Oriental.
Notable mountains and volcanoes include:
Chimborazo at 6,267 m (20,561 ft): an inactive volcano, the furthest point from Earth's center
Cotopaxi at 5,897 m (19,347 ft): the third-highest active volcano in the world
Illiniza Sur at 5,245 m (17,208 ft) and Illiniza Norte at 5,126 m (16,817 ft): twin volcanos separated by a saddle about 1 km (.6 mi) long
Tungurahua at 5,023 m (16,480 ft): an active volcano in eruption since 1998 near Baños-Tunguragua
Pichincha at 4,784 m (15,696 ft): a volcano overlooking the capital city of Quito
Topographic map of Ecuador
Sierra Natural Region
La Sierra, Ecuador's central Andean highlands region, covers approximately 70,000 sq km (27,000 sq mi), or about 25% of the country. The region's elevation, often 2,750 m (9,000 ft ) or more, gives the area a temperate climate.
The Sierra Natural Region contains ten major basins, each formed by transversal mountain spurs (nudos) connecting the Ecuadorian Andes' two main branches. These spurs were created by outpouring lava from the numerous volcanoes in the range.
The Nudo del Azuay, at 4,500 m (14,763 ft), is the highest of these transversal spurs. It divides the Sierra into two subregions: the area of modern volcanism to the north and the area of ancient volcanism to the south.
The northern area consists of newer, higher mountains than those in the southern ancient volcanism section, which eroded to lower levels with time.
The basins and their adjacent slopes, which are intensively cultivated, contain roughly half of Ecuador's population.
Most Ecuadorian cities are in these valleys, including Ibarra, Ambato, Riobamba, Mindo, Baños and Cuenca. Quito, the capital city, is located in a high mountain valley on the foothills of the Pichincha volcano.