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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 language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...
. 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
Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...
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 conti ...
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 Paci ...
. This approximately 1000 kilometer long, 90–230 km broad structure is an east–west, active, continental volcanic arc; encompassing an area of approximately 160,000 km2. Over several million years, the
subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...
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
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 Paci ...
along the northern end of the
Middle America Trench The Middle America Trench is a major subduction zone, an oceanic trench in the eastern Pacific Ocean off the southwestern coast of Middle America, stretching from central Mexico to Costa Rica. The trench is 1,700 miles (2,750 km) long an ...
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
stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and peri ...
es 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 faults, mantle plumes, continental rifting, 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 cones, shield volcanoes,
lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...
complexes, and major
calderas A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...
.


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 the o ...
deformation,
subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...
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 rifted 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'', ...
to the
Middle Miocene The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0.05 Ma to 11.608 ± 0.005 Ma (million ...
, 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 in ...
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 A basement or cellar is one or more Storey, floors of a building that are completely or partly below the storey, ground floor. It generally is used as a utility space for a building, where such items as the Furnace (house heating), furnace, ...
is highly heterogeneous. The Trans-Mexican Volcanic Belt east of 101°W rests upon
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...
terranes, assembled into the Oaxaquia microcontinent 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 fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its ow ...
. 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 which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...
- Early Jurassic siliclastic turbidites. 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 at approximately 23 Ma, which created two plates at equatorial latitudes, the Cocos Plate and southern
Nazca Plate The Nazca Plate or Nasca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction, along the Peru–Chile Trench, of the N ...
. 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 border ...
to the northeast, the
Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and I ...
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 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 atmos ...
rich rocks, and adakites 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 The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million year ...
. 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 and dacitic polygenetic volcanoes 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 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
Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...
, 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 The asthenosphere () is the mechanically weak and ductile region of the upper mantle of Earth. It lies below the lithosphere, at a depth between ~ below the surface, and extends as deep as . However, the lower boundary of the asthenosphere is ...
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 ignimbrites, 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 dacitic to
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 ...
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 rocks. This modern arc consists of a frontal belt dominated by
flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ...
and slab melting and a rear belt characterized by the differentiated rocks stated previously. Absent since ~9 Ma,
stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and peri ...
es 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 Michoacán–Guanajuato volcanic field is located in the Michoacán and Guanajuato states of central Mexico. It is a volcanic field that takes the form of a large cinder cone field, with numerous shield volcanoes and maars. Pico de Tancítaro ...
.


Cause of flat slab subduction

Flat slab subduction can commonly be explained by
oceanic plateau An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides. There are 184 oceanic plateaus in the world, covering an area of or about 5.11% of the ...
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. 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 from entering the mantle.


Geography


Region

From the west, the Trans-Mexican Volcanic Belt runs from Colima and
Jalisco Jalisco (, , ; Nahuatl: Xalixco), officially the Free and Sovereign State of Jalisco ( es, Estado Libre y Soberano de Jalisco ; Nahuatl: Tlahtohcayotl Xalixco), is one of the 31 states which, along with Mexico City, comprise the 32 Federal ...
east through northern
Michoacán Michoacán, formally Michoacán de Ocampo (; Purépecha: ), officially the Free and Sovereign State of Michoacán de Ocampo ( es, Estado Libre y Soberano de Michoacán de Ocampo), is one of the 32 states which comprise the Federal Entities of ...
, southern
Guanajuato Guanajuato (), officially the Free and Sovereign State of Guanajuato ( es, Estado Libre y Soberano de Guanajuato), is one of the 32 states that make up the Federal Entities of Mexico. It is divided into 46 municipalities and its capital city i ...
, southern
Querétaro Querétaro (), officially the Free and Sovereign State of Querétaro ( es, Estado Libre y Soberano de Querétaro, links=no; Otomi: ''Hyodi Ndämxei''), is one of the 32 federal entities of Mexico. It is divided into 18 municipalities. Its cap ...
,
México State The State of Mexico ( es, Estado de México; ), officially just Mexico ( es, México), is one of the 32 federal entities of the United Mexican States. Commonly known as Edomex (from ) to distinguish it from the name of the whole country, it is ...
, southern Hidalgo, the Distrito Federal, northern
Morelos Morelos (), officially the Free and Sovereign State of Morelos ( es, Estado Libre y Soberano de Morelos), is one of the 32 states which comprise the Federal Entities of Mexico. It is divided into 36 municipalities and its capital city is Cue ...
,
Puebla Puebla ( en, colony, settlement), officially Free and Sovereign State of Puebla ( es, Estado Libre y Soberano de Puebla), is one of the 32 states which comprise the Federal Entities of Mexico. It is divided into 217 municipalities and its cap ...
, 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 Political divisions of Mexico, Federal Entities of Mexico. It is ...
, 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 lies to the north, bounded by 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 ...
to the west and
Sierra Madre Oriental The Sierra Madre Oriental () is a mountain range in northeastern Mexico. The Sierra Madre Oriental is part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that f ...
to the east. The Cofre de Perote 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 Moun ...
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 lies between the Trans-Mexican Volcanic Belt and the
Sierra Madre del Sur The Sierra Madre del Sur is a mountain range in southern Mexico, extending from southern Michoacán east through Guerrero, to the Isthmus of Tehuantepec in eastern Oaxaca. Geography The Sierra Madre del Sur joins with the Eje Volcánico Tran ...
. This area is also a distinct physiographic province of the larger Sierra Madre System physiographic division. The Sierra de Ajusco-Chichinauhtzin also forms part of the belt.


Peaks

The highest point, also the highest point in Mexico, is
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 Moun ...
() 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 of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates ...
es. Other notable volcanoes in the range include (from west to east) Nevado de Colima (), Parícutin (),
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 (), Iztaccíhuatl (), Matlalcueitl () Cofre de Perote () 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 Neg ...
, 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 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 (''Aphelocoma ultramarina'').


See also

*
List of volcanoes in Mexico Types of volcanoes There are multiple types of volcanoes in Mexico. Volcanoes can be of different types such as cinder cone volcanoes, composite volcanoes, shield volcanoes, and lava domes. Each of these variations of volcanos forms in its ...
* List of seismic faults in Mexico *
Legend of Popocatépetl and Iztaccíhuatl A legend is a genre of folklore that consists of a narrative featuring human actions, believed or perceived, both by teller and listeners, to have taken place in human history. Narratives in this genre may demonstrate human values, and posses ...


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