The Ecuadorian Andes are divided into parallel volcanic cordilleras that form the central Andean highlands region of Ecuador. 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 which run in a slightly curved S-shape from north to south. The cordilleras were formed by the subduction of the Nazca Plate underneath the South American Plate.
The mountain system is essentially a 600 km- (375 mi-) long narrow plateau, bordered by primarily two parallel chains that contain numerous volcanoes. 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 includes 20 volcanoes, some of which have permanent snowcaps. A third cordillera has been identified in the eastern jungle of Ecuador and has been named the Cordillera Oriental.
In the south, the cordilleras are not well defined. A mountain mass in southern Ecuador, known as the Loja Knot, marks the transition between the Peruvian Andes and the Ecuadorian Andes.
Notable mountains and volcanoes include:
Chimborazo (6,267 m (20,561 ft)): inactive volcano, the furthest point from Earth's center
Cotopaxi (5,897 m (19,347 ft)): tallest active volcano in the world.
Illiniza (5,248 m (17,218 ft))
Tungurahua (5,023 m (16,480 ft)): active volcano in eruption since 1998 near Baños-Tunguragua
Pichincha (4,784 m (15,696 ft)): volcano overlooking the capital city of Quito
Topographic map of Ecuador
Sierra Natural Region
La Sierra, the central Andean highlands region of Ecuador, covers approximately 70,000 sq km (27,000 sq mi), or about 25% of the country. The elevation of the region, often 2,750 m (9,000 ft ) asl or more, gives the region a temperate climate.
The Sierra region contains ten major basins, each formed by transversal mountain spurs (nudos) that connect the two main branches of the Ecuadorian Andes. These spurs were created by the outpouring of 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 and 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 with time have eroded to lower levels.
The basins and their adjacent slopes, which are intensively cultivated, contain roughly half of Ecuador’s population. Most Ecuadorian cities are set 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.