relief – Geo-Mexico, the geography of Mexico

Altitude zones of Mexico

Dec 172016

Most of Mexico is above 1000 m (about 3300 ft) in elevation; as a result most of Mexico has a more temperate climate than might be expected given its latitude.

The famous explorer Alexander von Humboldt, one of the founding fathers of physical geography and meteorology, was the first to describe the vertical differentiation of climatic and vegetation zones in Mexico. Writing in 1811, he proposed the terms tierra caliente, tierra templada, and tierra fría, still widely used by non-specialists today.

Tierra caliente (hot land) includes all areas under about 900 m (3000 ft). These areas generally have a mean annual temperature above 25°C (77°F). Their natural vegetation is usually either tropical evergreen or tropical deciduous forest. Farms produce tropical crops such as sugar-cane, cacao and bananas.

Altitude zones. Copyright John Wiley & Sons Inc. 2000.

Tierra templada (temperate land) is the area between 900 and 1800 m (3000 to 6000 ft) where mean annual temperatures are usually between about 18°C and 25°C (64°F to 77°F). The natural vegetation in these zones is temperate forest, such as oak and pine-oak forest. Farms grow crops such as corn (maize), beans, squash, wheat and coffee.

Tierra fria (cold land) is over 1800 m (6000 ft) where mean annual temperatures are in the range 13°–18°C (55°–64°F). At these altitudes pine and pine-fir forests are common. Farm crops include barley and potatoes. On the highest mountain tops, above the tierra fría is tierra helada, frosty land.

Even higher, and almost permanently under snow and ice, is the tierra nevada, snow-covered land.

Common errors of Mexican geography #2: confusing the Sierra Madre with the Volcanic Axis

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Jun 192014

Describing somewhere in Mexico as being “located in the Sierra Madre mountains” may conjure up images of high, possibly snow-capped peaks and rugged scenery, but does very little to pin down the location. Mexico has several Sierras Madre (literal translation: Mother Ranges). The three main Sierra Madre regions in Mexico are the Western Sierra Madre, Eastern Sierra Madre and Southern Sierra Madre (see map).

The Western Sierra Madre (Sierra Madre Occidental) is the youngest, highest and most viciously dissected of the three. This region includes the scenically amazing Copper Canyon region we have described in many previous posts, including:

Location of Volcanic Axis and Monarch Butterfly reserves

The Western Sierra Madre extends only as far south as the states of Nayarit and Jalisco.

Its counterpart on the eastern side of the country is the Eastern Sierra Madre (Sierra Madre Oriental) which is older, lower and less rugged. Between these two major mountain ranges are mid-elevation basins and plains.

At the southern end of both the Western Sierra Madre and the Eastern Sierra Madre is the Volcanic Axis.

The Southern Sierra Madre (Sierra Madre del Sur) lies south of the Volcanic Axis, largely in the state of Oaxaca.

The details of Mexico’s physiographic regions are complex, but the basic relief pattern of these three Sierra Madre regions, separated by the Volcanic Axis and mid-elevation basins and plains, is fairly simple. It is therefore disappointing when we read references to the Sierra Madre regions that are geographically inaccurate.

The Monarch Butterfly reserves, for instance, are regularly described as being in the Sierra Madre, or the Western Sierra Madre, even though they are located hundreds of kilometers away from the Western Sierra Madre, on the southern edge of the Volcanic Axis (see map). In the original National Geographic article about the “discovery” of the Monarch Butterflies’ overwintering sites (August 1976), the location of the butterflies was deliberately left vague (to prevent human-induced disruption of the sites), so that article can readily be excused for mislocating the sites as being in “Mexico’s Sierra Madre”. (The tiny map that accompanied that article also shifted the Monarch’s wintering areas well away from their real position.)

Despite the efforts of the National Geographic, it was not long before journalists published articles giving the precise locations of the sites, and visitors started to flock to see this marvel of nature. The establishment of reserves has now brought a measure of sanity and control to access and most visitors now behave respectfully.

One of the latest in the long line of journals and magazines to erroneously refer to the site of the Monarch reserves as “in the remote Sierra Madre mountains” (but lacking the original excuse of the National Geographic) is the Canadian Geographic in its December 2013 Annual Wildlife Issue. The general tone of the article is helpful, and it rightly emphasizes the need to protect habitat along the entire migration route between Canada and Mexico, so why mar the overall quality by making such a basic error of Mexican geography? Let’s help educate readers by making it clear that the Monarch Butterfly reserves are not in any Sierra Madre, but are in the Volcanic Axis!

Mexico’s 15 physiographic regions

Excerpts from Geo-Mexico Comments Off

Jun 092014

The relief and landforms of Mexico have been greatly influenced by the interaction of tectonic plates.

The resulting relief patterns are so complex that it is often claimed that early explorers, when asked to describe what the new-found lands were like, simply crumpled up a piece of parchment by way of response.

The map below shows Mexico’s main physiographic regions. The core of Mexico (both centrally located, and where most of the population lives) is the Volcanic Axis (Region 10 on the map), a high plateau rimmed by mountain ranges to the west, south and east. Coastal plains lie between the mountains and the sea. The long Baja California Peninsula parallels the west coast. The low Isthmus of Tehuantepec separates the Chiapas Highlands and the low Yucatán Peninsula from the rest of Mexico.

We looked in more detail at the Volcanic Axis in several previous posts, including

and will look more closely at some of the other physiographic regions in later posts.

What is the elevation of Mexico’s cities?

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Feb 042013

The short answer to “What is the elevation of Mexico’s cities?” is “somewhere between zero and 3000 meters (8200 ft) above sea level!” Mexico’s extraordinarily varied relief provides settlement opportunities at a very wide range of elevations. Many Mexican cities are at or near sea level. This group includes not only coastal resort cities such as Acapulco, Cancún and Puerto Vallarta, but also Tijuana on the northern border and, at the opposite end of the country, Mérida, the inland capital of Yucatán state.

Mexico City, the nation’s capital, has an average elevation of about 2250 meters (7400 ft.), similar to that of nearby Puebla. Toluca, the capital city of the state of México, is almost 400 m higher, while both Huixquilucan and Zinacantepec (also in the state of México) are at an elevation of over 2700 meters. Moving northwards from Mexico City, numerous major cities are at elevations of between 1500 meters and 1850 meters above sea level. The cities nearer the lower end of this range include Saltillo, Oaxaca and Guadalajara, while Aguascalientes, Querétaro, Guanajuato, Morelia and León are all situated at elevations close to 1800 meters.

Frequency plot of city elevations in Mexico. Credit: Geo-Mexico

Are there more cities at some elevations than others? Each dot on the graph above represents one of Mexico’s 170 largest cities and towns, plotted against its average elevation. The two major clusters of cities occur at elevations of close to sea level and at 2250 meters, with another smaller, more spread out cluster between 1500 meters and 2000 meters. Perhaps somewhat surprisingly, there are relatively few Mexican cities at elevations of between 100 and 1500 meters (4920 ft.).

Q. Can you suggest any reasons for this? [Hint: Look at a relief map of Mexico to see how much land surface there actually is at different elevations].

The graph also shows the division of Mexico’s climate and vegetation zones by elevation first proposed by Alexander von Humbuldt following his visit to Mexico in 1803–1804. The terms tierra caliente, tierra templada, and tierra fría are still widely used by non-specialists today to describe the vertical differentiation of Mexico’s climatic and vegetation zones (see cross-section below).

Altitude zones. Copyright John Wiley & Sons Inc. 2000.

The tierra caliente (hot land) includes all areas under about 900 m (3000 ft). These areas generally have a mean annual temperature above 25°C (77°F). Their natural vegetation is usually either tropical evergreen or tropical deciduous forest. Farms produce tropical crops such as sugar-cane, cacao and bananas. Tierra templada (temperate land) describes the area between 900 and 1800 m (3000 to 6000 ft) where mean annual temperatures are usually between about 18°C and 25°C (64°F to 77°F). The natural vegetation in these zones is temperate forest, such as oak and pine-oak forest. Farms grow crops such as corn (maize), beans, squash, wheat and coffee. Tierra fria (cold land) is over 1800 m (6000 ft) where mean annual temperatures are in the range 13°–18°C (55°–64°F). At these altitudes pine and pine-fir forests are common. Farm crops include barley and potatoes. On the highest mountain tops, above the tierra fría is tierra helada, frosty land.

Interestingly, the tierra templada appears to have fewer cities than might be expected. Equally, while archaeologists have sometimes argued for the advantages of siting settlements close to the transition zone between climates, where a variety of produce from very distinct climates might be traded, the graph shows no evidence for this.

It would be misleading to read too much into this superficial analysis of the elevations of Mexican settlements. First, we have only considered the 170 largest settlements. Second, an individual settlement may extend over a range of elevation, so using an average figure does not reveal the entire picture. Thirdly, the precise elevations for tierra caliente, templada and fria all depend on the latitude and other local factors. Even so, it might be interesting to extend this analysis at some future time to include far more settlements to see if the patterns identified are still present or if others emerge.

Related posts:

Altitude zones of Mexico
Mexico’s Volcanic Axis

Mexico’s Volcanic Axis

Excerpts from Geo-Mexico Comments Off

Apr 192012

Mexico’s active seismic zones have created numerous volcanoes, many of which are still active. Virtually all the country’s active and recently dormant volcanoes are located in a broad belt of high relief which crosses Mexico from west to east: the Volcanic Axis (see map).

Altitudes in this region vary from a few hundred to several thousand meters. The principal peaks are shown on the map. They include many of Mexico’s most famous mountains, such as Popocatepetl and Iztaccihuatl, near Mexico City; Pico de Orizaba, Mexico’s highest peak; Paricutín, the only completely new volcano in the Americas in recent times; and Colima, considered the most active at present. Many of the volcanoes are surprisingly young. For instance, a study using Carbon‑14 dating on the palaeosols (ancient soils) under 12 volcanoes in the Toluca area yielded ages ranging from 38,600 to 8400 years before present.

It is unclear precisely why this broad belt of Mexico should be so active. Elsewhere in the world all major tectonically active areas have been linked in terms of their location to the margins or meeting‑zones of tectonic plates. Some Mexican geologists believe that Mexico’s Volcanic Axis is a rare example of activity associated with a gently dipping plate margin, one where the edge of the Cocos plate is subsumed, but at only moderate gradient, beneath the North American plate.

Almost all the volcanic activity in this zone has taken place in the last 25 million years, from the upper Oligocene period, through the Miocene and Pliocene and up to Recent. Two distinct periods of activity are recognized by some geologists. The first, in the late Oligocene and early Miocene, produced volcanic rocks often found today tightly folded by later earth movements. The second, responsible for all the major composite cones as well as dozens of ash and cinder cones, started in the Pliocene and continues today.

Erosion has had relatively little time to work on these “new” volcanic peaks, some of which are still developing. As a result, this region includes Mexico’s highest mountains, reaching over 5500 m or 18,000 ft.

Thick, lava-rich volcanic soils make this one of the most fertile areas in North America. Though the relief is very rugged, this area has supported relatively high population densities for hundreds of years, including the current large metropolitan areas of Mexico City, Guadalajara and Puebla. Legacies of previous volcanic activity are found in craters, mud‑volcanoes, geothermal activity, and the numerous hot springs (and spa towns) scattered throughout the Volcanic Axis.

Related posts:

Mexico’s Spanish language place names

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Feb 182010

The Spanish language is at least as rich as English when describing landscapes. Common Spanish geographical terms relating to landscape include:

cerro = hill
montaña = mountain
sierra = elongated mountain range
mesa = flat-topped (table) hill
cumbre = summit or peak
pico = sharp peak
valle = valley
barranca = canyon
cenote = limestone sinkhole
cabo = point or cape
punta = point or headland
arroyo = brook
río = river
lago = lake
salto, cascada = waterfall
ojo (de agua) = spring
presa = reservoir (and dam)
mar = sea
salinas = salt flats or salt works
golfo = gulf
bahía = bay
puerto = port (inland, puerto = pass)

[Extract from chapter 1 of Geo-Mexico: the geography and dynamics of modern Mexico]