Ecuador is divided into three continental regions--the Costa, Sierra, and Oriente--and one insular region--the Galápagos Islands. The continental regions extend the length of the country from north to south and are separated by the Andes Mountains. The Galápagos Islands, officially called the Archipiélago de Colón, are located 1,000 kilometers west of the Ecuadorian coast within 1 south of the equator.
The Costa, located between the Pacific Ocean and the Andes Mountains, consists of coastal lowlands, coastal mountains, and rolling hills that separate river valleys. The widest part of the region stretches 150 kilometers from Cabo San Lorenzo in Manabí Province to the foothills of the Andes Mountains. In the southern part of Guayas Province, east of the Gulf of Guayaquil, the narrow coastal plain is only fifteen to twenty kilometers wide. The lowlands of the Costa do not exceed 200 meters in elevation, whereas the coastal mountains extend no higher than 1,000 meters. The coastal mountain chain, known as the Cordillera Costañera, divides the region into the Costa Externa, next to the coast, and the Costa Internal, next to the Andes. The Cordillera Costañera reaches from Esmeraldas in the north to Guayaquil in the south. North of Portoviejo in Manabí Province, the Cordillera Costañera loses its character as a mountain chain and becomes a series of hills and small mountains.
The Sierra consists of two major chains of the Andes mountains, known as the Cordillera Occidental (Western Chain) and Cordillera Oriental (Eastern Chain), and the intermontane basin or plateau between the two chains. Several transversal mountain spurs, known as nudos, cut across the plateau. The Nudo del Azuay, at 4,500 meters the highest of these transversal spurs, divides the Sierra into two subregions--the area of modern volcanism to the north and the area of ancient volcanism to the south. The former area consists of newer, higher mountains than those in the ancient volcanism section, which with time have eroded to lower levels.
The Sierra has at least twenty-two peaks over 4,200 meters in height. Of the two cordilleras, the Cordillera Oriental is wider and generally higher, with peaks averaging over 4,000 meters. The Cordillera Occidental, however, contains the highest point in Ecuador, which is the Mount Chimborazo at 6,267 meters. The Sierra also contains the highest point on the equator, Mount Cayambe at 5,790 meters.
The Sierra has at least thirty peaks of volcanic origin, including six still active. These peaks, which vary in width from 80 to 130 kilometers, are located in the area of modern volcanism known as the Avenue of the Volcanos. The most active volcano is Mount Sangay, 5,230 meters high. Although its last major outpouring of lava occurred in 1946, specialists consider Mount Sangay to be in a constant state of eruption because of fires and bubbling lava at its crater. Mount Cotopaxi, at 5,897 meters the highest active volcano in the world, last erupted in 1877 and is now listed as "steaming." Its crater is 800 meters in diameter. In addition to the other damage caused by eruptions, volcanos in the Sierra have melted snowcaps, which in turn generate massive mudslides and avalanches. Earthquakes and tremors also are common in the region.
The intermontane plateau between the two cordilleras is divided by the nudos into roughly 10 basins, or hoyas, that range from 2,000 to 3,000 meters in altitude. The average altitude of the plateau is 2,650 meters.
The Oriente to the east of the Cordillera Oriental consists of two subregions: the Andean piedmont and the Eastern lowlands. The piedmont drops from a height of 3,353 meters to the featureless lowlands, which spread out at an altitude of 150 to 300 meters.
The Galápagos Islands consist of a chain of large, medium, and small islands that have a combined area of roughly 8,000 square kilometers. The largest island is Isabela Island, also known as Albemarle Island, which is 120 kilometers long with an area of 4,275 square kilometers. All of the islands are of volcanic origin, and some have active cones. Santo Tomás, located on Isabela Island, is the highest peak of the Galápagos at 1,490 meters. Its crater is ten kilometers in diameter.
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