The Sierra Madre is the principal mountain system of Mexico that encloses the central Mexican Plateau. Consisting of the Sierra Madre Oriental, Sierra Madre Occidental, Sierra Madre del Sur, and Sierra Madre de Oaxaca, the mountains form a broad northwest-southeast arc extending the length of Mexico.
The Sierra Madre is the principal mountain system of Mexico that encloses the central Mexican Plateau. Extending the length of Mexico, the mountains form a broad northwest-southeast arc.
The Sierra Madre mountain system includes:
Sierra Madre Occidental: mountain range in northwest Mexico
Sierra Madre Oriental: mountain range in northeast Mexico
Sierra Madre de Oaxaca: mountain range in south-central Mexico
Sierra Madre del Sur: mountain range in southern Mexico
Sierra Madre de Chiapas: mountain range in extreme southern Mexico, Guatemala, El Salvador, and Honduras
The Sierra Madre mountain system is part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of ridges that form the western backbone of North America, Central America, South America, and West Antarctica.
Topographic map of Mexico: Sierra Madre System
Sierra Madre Occidental
The primarily volcanic Sierra Madre Occidental is a primary mountain range system of the North American Cordillera that runs 1,250 km (780 mi) on a northwest-southeast course parallel to the Pacific coast of Mexico; through northwestern and western Mexico and along the Gulf of California.
Forming the western border of the Mexican Plateau, the range extends from northern Sonora state near the Mexico-U.S. border at Arizona, southeastwards to the Trans-Mexican Volcanic Belt and Sierra Madre del Sur ranges.
Deep river valleys, or barrancas, cut the high plateau formed by the range, the most spectacular of which is the complex known as Copper Canyon (Barranca del Cobre) in southwestern Chihuahua state. This plateau is formed from volcanic rock overlying a basement of metamorphic rock.
This uplift has caused changes in weather patterns; increased mountain rainfall has provided areas where ecosystems can form in wetter areas than the surrounding land. This water source creates watersheds that feed the arid surroundings with water, making it possible to irrigate and farm crops.
The wet ecosystems are islands of biodiversity, differing significantly from what would otherwise be a desert landscape. For example, oak forests are the predominant plant life and extend into the lowland deserts.
The Continental Divide in Mexico runs along the Sierra Madre Occidental. As the name suggests, the Continental Divide marks the point where watersheds are divided, determining the direction of water flow. In Mexico, the Sierra Madre Occidental is the primary geographical feature that forms the Continental Divide.
On the western side of the Sierra Madre Occidental, rivers and streams flow westward, eventually draining into the Pacific Ocean. On the eastern side, waterways flow eastward, ultimately contributing to the Gulf of Mexico and the Caribbean Sea, part of the Atlantic Ocean basin.
Sierra Madre Oriental
Spanning 1,000 km (620 mi), the Sierra Madre Oriental runs from the Rio Grande (on the border between Coahuila and Texas) south through Nuevo León, southwest Tamaulipas, San Luis Potosí, Querétaro, and Hidalgo; to northern Puebla where it joins with the east-west running Eje Volcánico Transversal of central Mexico.
The northernmost is the Sierra del Burro and the Sierra del Carmen, which reach the border with the United States at the Rio Grande. North of the Rio Grande, the range continues northwestward into Texas and beyond as the Davis and Guadalupe Ranges.
Mexico's Gulf Coastal Plain lies east of the range, between the mountains and the Gulf of Mexico coast. The Mexican Plateau, which averages 1,100 m (3,600 ft) in elevation, lies between the Sierra Madre Oriental and the Sierra Madre Occidental further west. The climate of the Sierra Madre Oriental is drier than the rainforest areas further south.
This extended range of tall mountains is noted for its abundant biodiversity and many endemic species of plants and wildlife, from the dry north to the wetter south. The Sierra Madre Oriental pine-oak forests are found at high elevations (1,000 - 3,500 m or 3,300 - 11,500 ft above sea level).
To the east, the Tamaulipan matorral occupies the range's lower slopes in Nuevo León and northern Tamaulipas. In comparison, the Veracruz moist forests cover the lower slopes of the central ridge, and the eastern slopes at the southern end of the range are home to the Veracruz montane forests.
West of the range, the Mexican Plateau is home to deserts and xeric shrublands, including the Chihuahuan Desert to the north, the Meseta Central Matorral on the central part of the plateau, and the Central Mexican Matorral on the southern plateau.
Elevation map of Mexico, including its main topography features.
Sierra Madre de Oaxaca
The Sierra Madre de Oaxaca mountain range is in southern Mexico, primarily in Oaxaca, extending north into Puebla and Veracruz.
The mountain range begins at Pico de Orizaba and extends southeasterly for 300 km (190 miles) until the Isthmus of Tehuantepec. Peaks in the Sierra Madre de Oaxaca average 2,500 m (8,200 ft) in elevation, with some peaks exceeding 3,000 m (9,800 ft).
The eastern slopes of the range are wetter, intercepting moisture-laden winds from the Gulf of Mexico. As a result, some drier valleys lie to the west in the rain shadow of the range.
The Sierra Madre de Oaxaca pine-oak forests ecoregion lies above 1,600 m (5,200 ft) in elevation. On the other hand, the humid Oaxacan montane forests ecoregion lies below 1,600 m (5,200 ft) in height on the eastern slopes above the Veracruz lowlands.
To the east, the xeric Tehuacan Valley matorral ecoregion occupies the Tehuacan Valley. To the northwest, the Jalisco dry forests ecoregion occupies the upper basin of the Santo Domingo River, which lies in the rain shadow of the Sierra Madre de Oaxaca.
The Southern Pacific, dry forests ecoregion, lies to the south along the Pacific Coast of Mexico, extending into the upper basin of the Tehuantepec River and the Valley of Oaxaca.
Culturally and geographically, the Sierra Madre de Oaxaca System can be split into many smaller sierras or sub-ranges, each with unique ecology and human culture.
Sierra Madre del Sur
The Sierra Madre del Sur is located in southern Mexico, extending 1,000 km (620 mi) from south Michoacán, east through Guerrero, to the Isthmus of Tehuantepec in eastern Oaxaca.
The Sierra Madre del Sur joins with the Eje Volcánico Transversal (Trans-Mexican Volcanic Belt) of central Mexico in northern Oaxaca but is separated from this range further west by the valley of the Río Balsas, and its tributary, the Río Tepalcatepec.
The mountains' highest point is 3,703 m (12,149 ft) in central Guerrero. Only one major highway crosses the range between Acapulco and Mexico City. The range is noted for its very high biodiversity and many endemic species.
The Sierra Madre del Sur pine-oak forests ecoregion occupies the higher reaches of the range. These forests are part of a chain of Mesoamerican pine-oak forests that stretch from the Southwestern United States to Costa Rica along the American Cordillera.
Tropical dry forests and ecoregions in the subtropical dry broadleaf forests biome cover the lower elevations. The Jalisco dry forests occupy the western end of the range's Pacific slope.
The Southern Pacific dry forests occupy most of the Pacific slope of the range, from Michoacan in the west through Guerrero and Oaxaca. The basin of the Balsas River, north of the Sierra, is home to the Balsas dry forests.
Topographic map of Mexico / Central America