Mountain systems
| Range | Where | Length km | Highest m |
|---|---|---|---|
| Sierra Madre Occidental | Sonora to Jalisco, parallel to the Pacific; Copper Canyon; Cerro Mohinora | 1,250 | 3,300 |
| Sierra Madre Oriental | Coahuila to Veracruz, parallel to the Gulf; Cerro El Potosí | 1,000 | 3,713 |
| Trans-Mexican Volcanic Belt | East–west at 19° N; Orizaba, Popocatépetl 5,426 m, Iztaccíhuatl 5,230 m | 900 | 5,636 |
| Sierra Madre del Sur | Guerrero and Oaxaca coast; Cerro Nube | 1,100 | 3,720 |
| Sierra Madre de Chiapas | Chiapas, into Guatemala; Tacaná volcano | 280 | 4,060 |
| Peninsular Ranges | Baja California; Picacho del Diablo | 1,000 | 3,096 |
Between the two Sierra Madres lies the Mexican Plateau (Altiplano), 1,000–2,500 m high, which holds most of the population. The volcanoes map covers the belt in detail and the Sierra Madre map the ranges.
Plates and the Middle America Trench
The relief has one main cause. Off the Pacific coast, from Jalisco south to Chiapas, the small Cocos and Rivera plates are being forced under the North American plate along the Middle America Trench, 50 to 150 km offshore and over 5,000 m deep. Cocos moves in at roughly 6 cm a year, Rivera more slowly. Melt off the sinking slab builds the volcanoes; friction on the plate interface makes the earthquakes — the 1985 magnitude 8.0 off Michoacán, felt 400 km inland, and both September 2017 shocks.
The Trans-Mexican Volcanic Belt is the anomaly. Volcanic arcs normally run parallel to their trench; this one crosses the country east to west at 19° N, obliquely to the coast. The explanation is slab geometry: beneath central Mexico the Cocos plate flattens almost horizontally before steepening again inland, pushing the melting zone north of where an ordinary arc would sit. That put Orizaba, the Nevado de Toluca and the Colima volcano on one line, and the basins of Mexico City, Puebla and Toluca between them.
The Gulf of California, a rift still opening
The north-west is different. The Gulf of California is not a bay but a young ocean basin: about six million years ago the Baja California peninsula was still attached to the mainland, and the plate boundary jumped inland to tear it away. Baja now rides north-west with the Pacific plate at about 5 cm a year, and the gulf is a chain of short spreading centres linked by transform faults — the same system that continues on land in California as the San Andreas. It is 1,100 km long and over 3,000 m deep in the south, so Baja California Sur is cut off from Sinaloa by deep water rather than by a plain.
Elevation, not latitude
Most of Mexico lies inside the tropics, so height, not latitude, decides what a place is like; mean elevation is 1,111 m. The bands Mexicans have always used are still the most useful reading of the terrain layer, and the climate map gives the temperatures that go with them.
| Band | Elevation m | Terrain | Examples |
|---|---|---|---|
| Tierra caliente | Below 1,000 | Coastal plain, the Yucatán, the Balsas floor; hot all year | Veracruz, Mérida, Acapulco |
| Tierra templada | 1,000–2,000 | Western plateau, coffee slopes of Veracruz | Guadalajara, Xalapa |
| Tierra fría | 2,000–4,000 | Central basins; frost normal in January | Mexico City, Toluca |
| Tierra helada | Above 4,000 | Permanent snow on the three great volcanoes | Orizaba, Popocatépetl |
Rivers and lakes
Mexico's rivers are short and seasonal because the mountains sit close to the coasts. The longest are the Río Bravo/Rio Grande (3,057 km, shared with the US), the Usumacinta (1,000 km, the largest by volume, on the Guatemalan border), the Grijalva (dammed for 40% of Mexico's hydropower), the Lerma–Santiago (the main interior system, feeding Lake Chapala and reaching the Pacific near Tepic) and the Balsas (drains the south-central highlands). Lake Chapala in Jalisco is the largest natural lake, about 1,100 km². See the rivers map.
The Balsas is a landform as much as a river: its basin of some 112,000 km² lies in a depression between the volcanic belt and the Sierra Madre del Sur, in rain shadow from both, so the valley floor in Guerrero drops to 200–500 m of hot scrub. In the north about a quarter of the country drains nowhere at all — the Nazas and Aguanaval end in the closed Laguna de Mayrán basin, the Bolsón de Mapimí across Chihuahua, Durango and Coahuila has no outlet, and Laguna Salada lies 10 m below sea level.
Karst, the Yucatán platform and the isthmus
The Yucatán Peninsula is the flattest part of the country and the one place where geology rather than relief does the work. It is a slab of marine limestone that rose out of the sea, and rain sinks straight through it, so north of Campeche there are no surface rivers: the drainage is underground. Collapsed cave roofs make the cenotes, several thousand known in Yucatán and Quintana Roo, with flooded systems mapped over 350 km long, and a ring of them traces the buried rim of the Chicxulub crater, 180 km across, left by the impact 66 million years ago.
Between Oaxaca and Chiapas the country narrows to the Isthmus of Tehuantepec: 215 km from the Gulf of Mexico to the Pacific over a pass of about 250 m, the lowest crossing of the cordillera south of the US border, which is why the highway and the interoceanic railway use it. It is also a wind gap: from October to February cold air banked over the Gulf pours through in gales, the Tehuantepecer, which drives cold-water upwelling off Oaxaca.
Deserts, jungle and coast
The north is desert and semi-desert (Chihuahuan, Sonoran). Chiapas and southern Veracruz have tropical rainforest (the Lacandon). The Pacific coast is rocky with deep bays; the Gulf coast is low, sandy and lagoon-fringed; the Caribbean coast has the Mesoamerican Reef, second-longest in the world. Mexico has about 11,122 km of coastline in all; the beaches map shows how differently the three sides behave.
Relief and biodiversity
Terrain explains the species count. Mexico is one of about 17 countries classed as megadiverse and carries roughly a tenth of the world's known species, a traverse from the coast to the crest of the Sierra crosses tropical forest, oak woodland, pine forest and alpine grassland inside 100 km, and each mountain block is cut off from the next by hot lowland. Mexico has more species of pine and of oak than any other country, and cloud forest, on windward slopes in Veracruz and Oaxaca, covers under 1% of the land but holds a tenth of its plants. More is on the state map.
Questions about Mexico's geography
What is the highest mountain in Mexico?
Pico de Orizaba (Citlaltépetl), 5,636 m, a dormant volcano on the Veracruz–Puebla line and the third-highest peak in North America. Popocatépetl (5,426 m) is second and is active.
Does Mexico have deserts?
Yes, two large ones: the Chihuahuan Desert (the largest in North America, about 360,000 km² across Chihuahua, Coahuila, Durango and into Texas and New Mexico) and the Sonoran Desert in Sonora and Baja California.
Why is Mexico City so high?
It sits in the Valley of Mexico at 2,240 m on the Trans-Mexican Volcanic Belt, a chain of volcanoes running east–west across the country at about 19° N. The valley was a lake bed, which is why the city subsides.
Why does Mexico have so many earthquakes?
The Cocos and Rivera plates are being pushed under the North American plate along the Middle America Trench, off the Pacific coast from Jalisco to Chiapas. The 1985 magnitude 8.0 earthquake began off the Michoacán coast, and the two September 2017 earthquakes (8.2 offshore Chiapas, 7.1 in Puebla and Morelos) came from the same system.
What is the lowest point in Mexico?
Laguna Salada, a dry lake bed in Baja California west of Mexicali, about 10 m below sea level. It shares a structural trough with California's Salton Sea and floods only when the Colorado River spills into it.