The Trans-Mexican Volcanic Belt ( es, Eje Volcánico Transversal), also known as the Transvolcanic Belt and locally as the (''Snowy Mountain Range''), is an active

volcanic belt A volcanic belt is a large volcanically active region. Other terms are used for smaller areas of activity, such as volcanic fields. Volcanic belts are found above zones of unusually high temperature () where magma is created by partial melting ...

that covers central-southern

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. Several of its highest peaks have snow all year long, and during clear weather, they are visible to a large percentage of those who live on the many high plateaus from which these volcanoes rise.

History

The Trans-Mexican Volcanic Belt spans across Central-Southern

from the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...

to the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...

between 18°30'N and 21°30'N, resting on the southern edge of the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacif ...

. This approximately 1000 kilometer long, 90–230 km broad structure is an east–west, active, continental

volcanic arc A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc lo ...

; encompassing an area of approximately 160,000 km². Over several million years, the subduction of the

Rivera Rivera () is the capital of Rivera Department of Uruguay. The border with Brazil joins it with the Brazilian city of Santana do Livramento, which is only a street away from it, at the north end of Route 5. Together, they form an urban area of aro ...

and Cocos plates beneath the

along the northern end of the Middle America Trench formed the Trans-Mexican Volcanic Belt. The Trans-Mexican Volcanic Belt is a unique volcanic belt; it is not parallel to the Middle American Trench, and many of the main stratovolcanoes are positioned obliquely to the general position of the arc. In addition to the physiographic complexities, igneous compositions vary—dominant subduction related products contrast with intraplate geo-chemical signatures. The many intriguing aspects of the belt has spurred several hypotheses based on a typical subduction scenario; Intra-plate

leaky transform fault A leaky transform fault is a transform fault with volcanic activity along a significant portion of its length producing new crust. In addition to the regular strike-slip motion observed at transform boundaries, an oblique extensional component i ...

mantle plume A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hot ...

s, continental

rifting In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben wi ...

, and jump of the eastward Pacific Rise. These features are partially related to the reactivation of early fault systems during the Trans-Mexican Volcanic belt's evolution. The main brittle fault system's geometry, kinematics, and age define a complex array of what could be multiple factors affecting the deformation of the belt. It exhibits many volcanic features, not limited to large stratovolcanoes, including

monogenetic volcano A monogenetic volcanic field is a type of volcanic field consisting of a group of small monogenetic volcanoes, each of which erupts only once, as opposed to polygenetic volcanoes, which erupt repeatedly over a period of time. The small monogeneti ...

cones,

shield volcanoes A shield volcano is a type of volcano named for its low profile, resembling a warrior's shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more vi ...

, lava dome complexes, and major calderas.

Geologic framework

Prior to the formation of the Trans-Mexican Volcanic Belt, an older, but related volcanic belt, the

Sierra Madre Occidental The Sierra Madre Occidental is a major mountain range system of the North American Cordillera, that runs northwest–southeast through northwestern and western Mexico, and along the Gulf of California. The Sierra Madre is part of the American ...

occupied the area. Resuming in the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

, post-

Laramide The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of th ...

deformation, subduction related volcanism formed the Sierra Madre Occidental silic volcanic arc at a paleo-subduction zone off the coast of

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

, before the peninsula

rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-grabe ...

ed away. From the

Late Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "d ...

to the Middle Miocene, counterclockwise rotation of the volcanic arc transitioned the once active Sierra Madre Occidental to a now active Trans-Mexican Volcanic Belt. By the Middle Miocene, the transition from the

silicic Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent. Granite and rhyolite are the most common silicic rocks. Silicic is the grou ...

to more

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks incl ...

compositions was complete, and can be considered the beginning of the Trans-Mexican Volcanic Belt. Due to the orthogonal orientation of the Trans-Mexican Volcanic Belt in relation to the trend of Mexican tectonic provinces, its Pre-

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

basement is highly heterogeneous. The Trans-Mexican Volcanic Belt east of 101°W rests upon Precambrian terranes, assembled into the Oaxaquia

microcontinent Continental crustal fragments, partly synonymous with microcontinents, are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin. Caus ...

and on the

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

Mixteco

terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust (geology), crust fragment formed on a tectonic plate (or broken off from it) and Accretion (geology), accreted or "Suture (geology), sutured" to crust lying on another pla ...

. West of 101°W, the Trans-Mexican Volcanic Belt resides on top of the Guerro composite terrane - a make up of

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

to Cretaceous marine marginal arcs, which are built on

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

- Early Jurassic siliclastic

turbidite A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing Turbidites wer ...

s. Assemblage of these basement rocks results with a thickness of 50–55 km east of 101°W and 35–40 km west of 101°W.

Plate evolution

The subducting plates originated from the breakup of the

Farallon Plate The Farallon Plate was an ancient oceanic plate. It formed one of the three main plates of Panthalassa, alongside the Phoenix Plate and Izanagi Plate, which were connected by a triple junction. The Farallon Plate began subducting under the west ...

at approximately 23 Ma, which created two plates at equatorial latitudes, the Cocos Plate and southern Nazca Plate. The Rivera Plate was the last fragment detached from the Cocos Plate, becoming a microplate at around 10 Ma. This small plate is bounded by the Rivera fracture zone, the

East Pacific Rise The East Pacific Rise is a mid-ocean rise (termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), a divergent tectonic plate boundary located alon ...

, the Tamayo fracture zone, and the Middle American Trench. The larger Cocos Plate is bordered by the North American Plate (NAM) and the

Caribbean Plate The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America. Roughly 3.2 million square kilometers (1.2 million square miles) in area, the Caribbean Plate borders ...

to the northeast, the Pacific Plate to the west, and to the south by the Nazca Plate. The Cocos and Rivera are relatively young oceanic plates (25 and 10 Ma) that are subducting along the Middle American Trench at different convergence rates (Rivera = ~30 mm/yr and the Cocos = ~ 50–90 mm/yr). Commonly found subduction related rocks such as

calc-alkaline The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic m ...

rocks volumetrically occupy a majority of the Trans-Mexican Volcanic Belt but smaller volumes of intraplate-like lavas,

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...

rich rocks, and

adakite Adakites are volcanic rocks of intermediate to felsic composition that have geochemical characteristics of magma originally thought to have formed by partial melting of altered basalt that is subducted below volcanic arcs. Most magmas derived ...

s are associated with the area. Middle Miocene adakitic (more felsic) rocks are found furthest from the trench and along the volcanic front of the central Trans-Mexican Volcanic Belt during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Quaternary. It has been suggested that slab melting contributed to the adakitic imprint on the Trans-Mexican Volcanic Belt, prompted by the prolonged flat subduction of the Cocos Plate.

Belt evolution

Formation

# From the early to mid Miocene ~20 to 8 Ma, the initial Trans-Mexican Volcanic Belt volcanic arc consisted of intermediate effusive volcanism, producing

andesitic Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomin ...

and

dacitic Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyol ...

polygenetic volcanoes Polygenesis can refer to: * Polygenesis (linguistics), a theory of language origin * Polygenism, a theory of human origin * Gene duplication Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through w ...

extending from western Michoacan (longitude 102°W) to the Palma Sola area (longitude 98°30'). The plate boundary geometry and sub-horizontal subducting slab's thermal structure are the controlling factors for initial arc volcanism. Magmatism migrated away from the trench, moving northeast towards the Gulf of Mexico—giving the arc its characteristic E-W orientation, the inland push of the arc showed progressively drier melting, and eventually

slab Slab or SLAB may refer to: Physical materials * Concrete slab, a flat concrete plate used in construction * Stone slab, a flat stone used in construction * Slab (casting), a length of metal * Slab (geology), that portion of a tectonic plate tha ...

melting began to occur—suggesting flattening of the subducted slab. The oldest rocks of this age may be exposed near the modern volcanic front, in Central Mexico. # A Late Miocene ~11 Ma eastward traveling pulse of mafic volcanism swept across the whole of Central

, north of the previously formed arc, ending ~ 3 Ma. The onset of the mafic lavas indicates lateral propagation of slab tear, prompted by the end of subduction beneath Baja California, allowing the influx of asthenosphere into the

mantle wedge A mantle wedge is a triangular shaped piece of mantle that lies above a subducting tectonic plate and below the overriding plate. This piece of mantle can be identified using seismic velocity imaging as well as earthquake maps. Subducting oceanic ...

. This volcanism created basaltic plateaus through fissures, or less commonly, small shield volcanoes and lava cones, with diminishing lava volume eastward. # West of 103°W, silicic volcanism between 7.5 and 3.0 Ma became

bimodal In statistics, a multimodal distribution is a probability distribution with more than one mode. These appear as distinct peaks (local maxima) in the probability density function, as shown in Figures 1 and 2. Categorical, continuous, and d ...

(mafic-silicic) in the early Pliocene, creating large dome complexes and

ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surro ...

s, and marked the beginning of trenchward migration of volcanism. East of 101°W dome complexes, lava flows, and large calderas that produced significant quantities of ignimbrites (>50 km³) of

rhyolitic Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...

composition can be found dating between 7.5 and 6 Ma. There is an absence of silicic volcanism between these regions during the whole Trans-Mexican Volcanic Belt history. Since the late Miocene, silicic volcanism migrated trenchward over 200 km in the eastern sector (east of 101°W) and 100 km in the western sector (West of 103°W). # Since the late Pliocene, the style and composition of volcanism in the Trans-Mexican Volcanic Belt became more diverse. In several areas, volumetrically dominant calc-alkaline rocks are associated with modest volumes of intraplate-like lavas or other potassium rich rocks, accompanied by Quaternary rhyolitic

peralkaline rock Peralkaline rocks include those igneous rocks which have a deficiency of aluminium such that sodium and potassium are in excess of that needed for feldspar. The presence of aegerine (sodium pyroxene) and riebeckite (sodium amphibole) are indicati ...

s. This modern arc consists of a frontal belt dominated by flux and slab melting and a rear belt characterized by the differentiated rocks stated previously. Absent since ~9 Ma, stratovolcanoes began to be created in the last 1 Ma ~100 km behind the volcanic front in the Western Sector, oriented West - Northwest and East - Southeast. In the eastern sector, all stratovolcanoes are found within the volcanic front. One exception to the location of these stratovolcanoes is the Colima volcanic complex, which is positioned south of the southern tip of the Cocos and Rivera slab tear and is the largest volcanic edifice in the Trans-Mexican Volcanic Belt. In addition to stratovolcanoes, monogenetic volcanic fields are also characteristic for this episode, the most prominent being the Michoacán–Guanajuato volcanic field.

Cause of flat slab subduction

Flat slab subduction Flat slab subduction is characterized by a low subduction angle (<30 degrees to horizontal) beyond the

seismogenic layer

can commonly be explained by oceanic plateau subduction and a fast overriding plate. Central Mexico's flat subduction is not evident. The Trans-Mexican Volcanic belt's flat slab is confined between ~101°W and 96°W; this region may be explained by thicker

continental crust Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called '' sial'' be ...

. Existence of thick strong crust combined with decreasing fluid input contributed to narrowing the asthenospheric wedge, increasing viscosity and suction forces, which led to flat subduction—preventing the

oceanic plate Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic c ...

from entering the mantle.

Geography

Region

From the west, the Trans-Mexican Volcanic Belt runs from

Colima Colima (), officially the Free and Sovereign State of Colima ( es, Estado Libre y Soberano de Colima), is one of the 31 states that make up the 32 Federal Entities of Mexico. It shares its name with its capital and main city, Colima. Colima i ...

and Jalisco east through northern Michoacán, southern Guanajuato, southern Querétaro, México State, southern

Hidalgo Hidalgo may refer to: People * Hidalgo (nobility), members of the Spanish nobility * Hidalgo (surname) Places Mexico * Hidalgo (state), in central Mexico * Hidalgo, Coahuila, a town in the north Mexican state of Coahuila * Hidalgo, Nuevo Le� ...

, the

Distrito Federal A federal district is a type of administrative division of a federation, usually under the direct control of a federal government and organized sometimes with a single municipal body. Federal districts often include capital districts, and they ...

, northern Morelos, Puebla, and

Tlaxcala Tlaxcala (; , ; from nah, Tlaxcallān ), officially the Free and Sovereign State of Tlaxcala ( es, Estado Libre y Soberano de Tlaxcala), is one of the 32 states which comprise the Federal Entities of Mexico. It is divided into 60 municipaliti ...

, to central

Veracruz Veracruz (), formally Veracruz de Ignacio de la Llave (), officially the Free and Sovereign State of Veracruz de Ignacio de la Llave ( es, Estado Libre y Soberano de Veracruz de Ignacio de la Llave), is one of the 31 states which, along with Me ...

. The

Mexican Plateau The Central Mexican Plateau, also known as the Mexican Altiplano ( es, Altiplanicie Mexicana), is a large arid-to-semiarid plateau that occupies much of northern and central Mexico. Averaging above sea level, it extends from the United States b ...

lies to the north, bounded by the

to the west and Sierra Madre Oriental to the east. The

Cofre de Perote Cofre de Perote, also known by its Nahuatl names Naupa-Tecutépetl (from ''Nāuhpa-Tēuctēpetl'') and Nauhcampatépetl, both meaning something like "Place of Four Mountains" or "Mountain of the Lord of Four Places", is an inactive volcano loca ...

and

Pico de Orizaba Pico de Orizaba, also known as Citlaltépetl (from Nahuatl = star, and = mountain), is an inactive stratovolcano, the highest mountain in Mexico and the third highest in North America, after Denali of Alaska in the United States and Mount ...

volcanoes, in Puebla and Veracruz, mark the meeting of the Trans-Mexican Volcanic Belt with the Sierra Madre Oriental. To the south, the basin of the

Balsas River The Balsas River (Spanish Río Balsas, also locally known as the Mezcala River, or Atoyac River) is a major river of south-central Mexico. The basin flows through the states of Guerrero, México, Morelos, and Puebla. Downstream of Ciudad Alta ...

lies between the Trans-Mexican Volcanic Belt and the Sierra Madre del Sur. This area is also a distinct physiographic province of the larger Sierra Madre System physiographic division. The

Sierra de Ajusco-Chichinauhtzin The Sierra del Ajusco-Chichinauhtzin, (Ajusco-Chichinautzin Mountain Range) also known as ''Serranía del Ajusco'' or ''Sierra de Chichinauhtzin'', is a Mexican mountain range located between Mexico City and the states of Morelos and Mexico. It m ...

also forms part of the belt.

Peaks

The highest point, also the highest point in Mexico, is

() also known as Citlaltépetl, located at . This, and several of the other high peaks, are active or dormant

volcano A volcano is a rupture in the Crust (geology), crust of a Planet#Planetary-mass objects, planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and volcanic gas, gases to escape from a magma chamber below the surface. On Ear ...

es. Other notable volcanoes in the range include (from west to east)

Nevado de Colima Nevado (1813? – 1821) was a Mucuchies dog that was given to Simón Bolívar by the local people of Mucuchíes, Mérida, in the Venezuelan Andes. It was given as a kind of present shortly after the Battle of Niquitao during his triumphal A ...

(),

Parícutin Parícutin (or Volcán de Parícutin, also accented Paricutín) is a cinder cone volcano located in the Mexican state of Michoacán, near the city of Uruapan and about west of Mexico City. The volcano surged suddenly from the cornfield of loca ...

(),

Nevado de Toluca Nevado de Toluca () is a stratovolcano in central Mexico, located about west of Mexico City near the city of Toluca. It is the fourth highest of Mexico's peaks, after Pico de Orizaba, Popocatépetl and Iztaccíhuatl. The volcano and the area ar ...

(),

Popocatépetl Popocatépetl (; Nahuatl: ) is an active stratovolcano located in the states of Puebla, Morelos, and Mexico in central Mexico. It lies in the eastern half of the Trans-Mexican volcanic belt. At it is the second highest peak in Mexico, after C ...

(),

Iztaccíhuatl Iztaccíhuatl (alternative spellings include Ixtaccíhuatl, or either variant spelled without the accent) ( or, as spelled with the x, ), is a dormant volcanic mountain in Mexico located on the border between the State of Mexico and Puebla withi ...

(), Matlalcueitl ()

() and

Sierra Negra Sierra Negra (also, and perhaps more properly, Cerro La Negra) is an extinct volcano located in the Mexican state of Puebla, close to the border with Veracruz. At officially above sea level, it is the fifth-highest peak in Mexico. Sierra Ne ...

, a companion of the Pico de Orizaba ().

Ecology

The mountains are home to the Trans-Mexican Volcanic Belt pine-oak forests, one of the

Mesoamerican pine-oak forests Mesoamerica is a historical region and cultural area in southern North America and most of Central America. It extends from approximately central Mexico through Belize, Guatemala, El Salvador, Honduras, Nicaragua, and northern Costa Rica. Withi ...

sub-

ecoregion An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of ...

s. The Trans-Mexican Volcanic Belt has many endemic species, including the

Transvolcanic jay The jay (''Aphelocoma ultramarina'') is a bird endemic to Mexico. Description It is a medium-large (~120 g) passerine bird similar in size to most other jays, with a blue head, blue-gray mantle, blue wings and tail, gray breast and underparts. ...

(''Aphelocoma ultramarina'').

References

External links

Mexico Volcanoes and Volcanics USGS
* {{Authority control Mountain ranges of Mexico Physiographic provinces Physiographic regions of Mexico Volcanic belts Volcanism of Mexico Landforms of Hidalgo (state) Landforms of Mexico City Landforms of Michoacán Landforms of the State of Mexico Landforms of Morelos Landforms of Puebla Landforms of Veracruz Landforms of Tlaxcala Neogene Mexico Quaternary Mexico Neogene volcanism Quaternary volcanism