A pine is any conifer in the genus Pinus of the family Pinaceae. Pinus is the sole genus in the subfamily Pinoideae; the Plant List compiled by the Royal Botanic Gardens and Missouri Botanical Garden accepts 126 species names of pines as current, together with 35 unresolved species and many more synonyms. The modern English name "pine" derives from Latin pinus, which some have traced to the Indo-European base *pīt- ‘resin’. Before the 19th century, pines were referred to as firs. In some European languages, Germanic cognates of the Old Norse name are still in use for pines—in Danish fyr, in Norwegian fura/fure/furu, Swedish fura/furu, Dutch vuren, German Föhre—but in modern English, fir is now restricted to fir and Douglas fir. Pine trees are evergreen, coniferous resinous trees growing 3–80 m tall, with the majority of species reaching 15–45 m tall; the smallest are Siberian dwarf pine and Potosi pinyon, the tallest is an 81.79 m tall ponderosa pine located in southern Oregon's Rogue River-Siskiyou National Forest.
Pines are long lived and reach ages of 100–1,000 years, some more. The longest-lived is Pinus longaeva. One individual of this species, dubbed "Methuselah", is one of the world's oldest living organisms at around 4,600 years old; this tree can be found in the White Mountains of California. An older tree, now cut down, was dated at 4,900 years old, it was discovered in a grove beneath Wheeler Peak and it is now known as "Prometheus" after the Greek immortal. The bark of most pines is thick and scaly; the branches are produced in regular "pseudo whorls" a tight spiral but appearing like a ring of branches arising from the same point. Many pines are uninodal, producing just one such whorl of branches each year, from buds at the tip of the year's new shoot, but others are multinodal, producing two or more whorls of branches per year; the spiral growth of branches and cone scales may be arranged in Fibonacci number ratios. The new spring shoots are sometimes called "candles"; these "candles" offer foresters a means to evaluate fertility of the vigour of the trees.
Pines have four types of leaf: Seed leaves on seedlings are borne in a whorl of 4–24. Juvenile leaves, which follow on seedlings and young plants, are 2–6 cm long, green or blue-green, arranged spirally on the shoot; these are produced for six months to five years longer. Scale leaves, similar to bud scales, are small and not photosynthetic, arranged spirally like the juvenile leaves. Needles, the adult leaves, are green and bundled in clusters called fascicles; the needles can number from one to seven per fascicle, but number from two to five. Each fascicle is produced from a small bud on a dwarf shoot in the axil of a scale leaf; these bud scales remain on the fascicle as a basal sheath. The needles persist depending on species. If a shoot is damaged, the needle fascicles just below the damage will generate a bud which can replace the lost leaves. Pines are monoecious, having the male and female cones on the same tree, though a few species are sub-dioecious, with individuals predominantly, but not wholly, single-sex.
The male cones are small 1–5 cm long, only present for a short period, falling as soon as they have shed their pollen. The female cones take 1.5–3 years to mature after pollination, with actual fertilization delayed one year. At maturity the female cones are 3–60 cm long; each cone has numerous spirally. The seeds are small and winged, are anemophilous, but some are larger and have only a vestigial wing, are bird-dispersed. At maturity, the cones open to release the seeds, but in some of the bird-dispersed species, the seeds are only released by the bird breaking the cones open. In others, the seeds are stored in closed cones for many years until an environmental cue triggers the cones to open, releasing the seeds; the most common form of serotiny is pyriscence, in which a resin binds the cones shut until melted by a forest fire. Pines are gymnosperms; the genus is divided into two subgenera, which can be distinguished by cone and leaf characters: Pinus subg. Pinus, the yellow, or hard pine group with harder wood and two or three needles per fascicle Pinus subg.
Strobus, the white, or soft pine group with softer wood and five needles per fascicle Pines are native to the Northern Hemisphere, in a few parts of the tropics in the Southern Hemisphere. Most regions of the Northern Hemisphere host some native species of pines. One species crosses the equator in Sumatra to 2°S. In North America, various species occur in regions at latitudes from as far north as 66°N to as far south as 12°N. Pines may be found in a large variety of environments, ranging from semi-arid desert to rainforests, from sea level up to 5,200 metres, from the coldest to the hottest environments on Earth, they occur in mountainous areas with favorable soils and at least some water. Various species have been introduced to temperate and subtropical regions of both hemisp
Mexico the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States. Covering 2,000,000 square kilometres, the nation is the fifth largest country in the Americas by total area and the 13th largest independent state in the world. With an estimated population of over 120 million people, the country is the eleventh most populous state and the most populous Spanish-speaking state in the world, while being the second most populous nation in Latin America after Brazil. Mexico is a federation comprising 31 states and Mexico City, a special federal entity, the capital city and its most populous city. Other metropolises in the state include Guadalajara, Puebla, Tijuana and León. Pre-Columbian Mexico dates to about 8000 BC and is identified as one of five cradles of civilization and was home to many advanced Mesoamerican civilizations such as the Olmec, Teotihuacan, Zapotec and Aztec before first contact with Europeans. In 1521, the Spanish Empire conquered and colonized the territory from its politically powerful base in Mexico-Tenochtitlan, administered as the viceroyalty of New Spain.
Three centuries the territory became a nation state following its recognition in 1821 after the Mexican War of Independence. The post-independence period was tumultuous, characterized by economic inequality and many contrasting political changes; the Mexican–American War led to a territorial cession of the extant northern territories to the United States. The Pastry War, the Franco-Mexican War, a civil war, two empires, the Porfiriato occurred in the 19th century; the Porfiriato was ended by the start of the Mexican Revolution in 1910, which culminated with the promulgation of the 1917 Constitution and the emergence of the country's current political system as a federal, democratic republic. Mexico has the 11th largest by purchasing power parity; the Mexican economy is linked to those of its 1994 North American Free Trade Agreement partners the United States. In 1994, Mexico became the first Latin American member of the Organisation for Economic Co-operation and Development, it is classified as an upper-middle income country by the World Bank and a newly industrialized country by several analysts.
The country is considered both a regional power and a middle power, is identified as an emerging global power. Due to its rich culture and history, Mexico ranks first in the Americas and seventh in the world for number of UNESCO World Heritage Sites. Mexico is an ecologically megadiverse country, ranking fourth in the world for its biodiversity. Mexico receives a huge number of tourists every year: in 2018, it was the sixth most-visited country in the world, with 39 million international arrivals. Mexico is a member of the United Nations, the World Trade Organization, the G8+5, the G20, the Uniting for Consensus group of the UN, the Pacific Alliance trade bloc. Mēxihco is the Nahuatl term for the heartland of the Aztec Empire, namely the Valley of Mexico and surrounding territories, with its people being known as the Mexica, it is believed to be a toponym for the valley which became the primary ethnonym for the Aztec Triple Alliance as a result, although it could have been the other way around.
In the colonial era, back when Mexico was called New Spain this territory became the Intendency of Mexico and after New Spain achieved independence from the Spanish Empire it came to be known as the State of Mexico with the new country being named after its capital: the City of Mexico, which itself was founded in 1524 on top of the ancient Mexica capital of Mexico-Tenochtitlan. Traditionally, the name Tenochtitlan was thought to come from Nahuatl tetl and nōchtli and is thought to mean "Among the prickly pears rocks". However, one attestation in the late 16th-century manuscript known as "the Bancroft dialogues" suggests the second vowel was short, so that the true etymology remains uncertain; the suffix -co is the Nahuatl locative, making the word a place name. Beyond that, the etymology is uncertain, it has been suggested that it is derived from Mextli or Mēxihtli, a secret name for the god of war and patron of the Mexica, Huitzilopochtli, in which case Mēxihco means "place where Huitzilopochtli lives".
Another hypothesis suggests that Mēxihco derives from a portmanteau of the Nahuatl words for "moon" and navel. This meaning might refer to Tenochtitlan's position in the middle of Lake Texcoco; the system of interconnected lakes, of which Texcoco formed the center, had the form of a rabbit, which the Mesoamericans pareidolically associated with the moon rabbit. Still another hypothesis suggests that the word is derived from Mēctli, the name of the goddess of maguey; the name of the city-state was transliterated to Spanish as México with the phonetic value of the letter x in Medieval Spanish, which represented the voiceless postalveolar fricative. This sound, as well as the voiced postalveolar fricative, represented by a j, evolved into a voiceless velar fricative during the 16th century; this led to the use of the variant Méjico in many publications in Spanish, most notably in Spain, whereas in Mexico and most other Spanish–speaking countries, México was the preferred spelling. In recent years, the Real Academia Española, which regulates the Spanish l
The Mexican jay known as the gray-breasted jay, is a New World jay native to the Sierra Madre Oriental, Sierra Madre Occidental, Central Plateau of Mexico and parts of the southwestern United States. In May 2011, the American Ornithologists' Union voted to split the Mexican jay into two species, one retaining the common name Mexican jay and one called the Transvolcanic jay; the Mexican jay is a medium-sized jay with pale gray underparts. It has an unstreaked throat and breast, it feeds on acorns and pine nuts, but includes many other plant and animal foods in its diet. It has a cooperative breeding system where the parents are assisted by other birds to raise their young; this is a common species with a wide range and the International Union for Conservation of Nature has rated its conservation status as being of "least concern". It is native to the Sierra Madre Oriental, Sierra Madre Occidental, Central Plateau of Mexico as well as eastern Arizona, western New Mexico and western Texas in the United States.
Its preferred habitat is montane pine-oak forest. The Mexican jay is a medium-large passerine similar in size to most other jays, with a blue head, blue-gray mantle, blue wings and tail, pale gray breast and underparts; the sexes are morphologically similar, juveniles differ only in having less blue coloration and, in some populations, a pink/pale bill that progressively becomes more black with age. Some field guides misreport this color as yellow because the pale bill becomes yellow in museum study skins; the iris is brown and legs are black. It is most distinguished from the similar western scrub jay by the plain throat and breast, the mantle contrasting less with the head and wings, its range somewhat overlaps with the western scrub-jays, where they co-occur, the two species seem to show ecological and morphological character displacement. In the winter, the Mexican jay's diet consists of acorns and pine nuts, which are stored in the autumn. However, they are omnivorous in all seasons and their diet includes a wide variety of plant and animal matter, including invertebrates, small amphibians and reptiles, birds' eggs and nestlings.
It has a cooperative breeding system similar to that of the related Florida scrub-jay, with several birds helping at a nest. A recent decision by the American Ornithologists' Union Check-list Committee elevated some populations of the Mexican jay to a separate species, called the Transvolcanic jay, based on diagnosable phenotypic differences in plumage and morphology, millions of years of genetic divergence and no evidence for interbreeding with Mexican jays; the Transvolcanic jay inhabits montane forest in the Transvolcanic Belt of central Mexico. Populations to the north retained the common name Mexican jay, but the Latin name changed to A. wollweberi. This was because the type specimen was a Transvolcanic jay, meaning that this species had precedent for the original Latin name A. ultramarina. Thus, as of this decision, there are now five described subspecies of Mexican jays that are divided into three divergent groups. Marked differences in size, color and genetics have led some authors to consider at least two of these groups as separate species.
The three groups inhabit three distinct mountainous regions in central Mexico. Genetic breaks in mitochondrial and microsatellite DNA occur abruptly between the groups, indicating some barriers to genetic exchange. Size variation among the groups does not always follow Bergmann's rule, with more southerly populations in the Sierra Madre Oriental being larger than populations to the north. Mexican jays do not seem to follow Gloger's rule either, as populations in arid habitat in southwestern Texas are blue. On the other hand, Mexican jays in Arizona - arid habitat - have a washed-out appearance, in accordance with Gloger's rule. Western groupSierra Madre Occidental in northern north to central Arizona and southwestern New Mexico. Southern and eastern limits in Jalisco deserve further study. Juveniles have a pink/pale base to the otherwise black bill for up to two years. Eggs are unspeckled, unlike Eastern group where speckled eggs are common. Aphelocoma wollweberi gracilisE Nayarit and N Jalisco Smallest of the Western subspecies with a distinct, high-pitched vocalization.
Aphelocoma wollweberi wollweberiDurango and Zacatecas Intermediate in size. Aphelocoma wollweberi arizonaeSonora and Chihuahua north to Arizona and New Mexico, United States Largest and most pale of all subspecies. Eastern groupSierra Madre Oriental in Nuevo León and W Tamaulipas north to Texas. Juveniles have an all-black exterior to the bill after fledging, but roof of inner upper mandible can remain white for up to two years. Reports of less social behavior compared to other groups are over-stated and credible accounts of cooperative breeding and large flock sizes exist. Plain and white eggs have been observed in a single study area. Aphelocoma wollweberi couchiiSmaller than preceding. Population of latter species distinguishable by more contrasting markings and ecological preferences. Egg color may range from plain blue to nile blue with pale brownish speckling, most heavy on blunt half. Gives rattle call similar to Cyanocitta and w
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, along the Gulf of California. The Sierra Madre is part of the American Cordillera, a chain of mountain ranges that consists of an continuous sequence of mountain ranges that form the western'backbone' of North America, Central America, South America and West Antarctica; the Spanish name sierra madre means "mother mountains" in English, occidental means "western", these thus being the "Western Mother Mountains". To the east, from the Spanish oriental meaning "eastern" in English, the Sierra Madre Oriental range or "Eastern Mother Mountains" runs parallel to the Sierra Madre Occidental along eastern Mexico and the Gulf of Mexico; 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; the high plateau, formed by the range is cut by deep river valleys.
This plateau is formed from volcanic rock overlying a basement of metamorphic rock. This uplift has caused changes in weather patterns; this water source forms watersheds that provide the arid surroundings with water that makes it possible to irrigate and farm crops. The wet ecosystems are islands of biodiversity, differing from what would otherwise be a desert landscape. Oak forests are the predominant plant life, extend into the lowland deserts; this forest and canyon land provided a place for a variety of indigenous people to live, until Spanish settlers with associated mestizos came into the area to found towns for the silver mines in the area. The major industries in the area now are agriculture and forestry, which have become contentious because of land degradation and the native population's opposition to these practices; the range trends from the north to southeast. Canyons cut by the rivers of the wet western slopes exist in addition to those of the northeast slopes, notably the Copper Canyon.
The range runs parallel to the Pacific coast of Mexico, from just south of the Arizona-Sonora border southeast through eastern Sonora, western Chihuahua, Durango, Nayarit, Aguascalientes to Guanajuato, where it joins with the Sierra Madre del Sur and the Eje Volcánico Transversal of central Mexico after crossing 1,250 km. The mountains range from 300 km from the Gulf of California in the north, but begin to approach within 50 km of the Pacific in the south; these mountains are considered to be part of the much larger American cordillera, the mountains extending from Alaska down to these across western North America. Sierra Tarahumara or Tarahumara is the name for the region of the Sierra Madre beginning at the Durango border and extending north; this name comes from the Tarahumara natives. This is a dramatic landscape of steep mountains formed by a high plateau, cut through with canyons including Copper Canyon, larger and, in places, deeper than the Grand Canyon; this plateau has an average elevation of 2,250 m with most of the more eroded canyons on the western slope, due to the higher moisture content.
The highest elevations occur in the Tarahumara range. The exact elevations of the highest peaks are not known within accurate enough ranges to determine their relative elevation; the highest point is Cerro Mohinora, located at 25°57′N 107°03′W. Estimates for the height of the mountain start around 3,040 m and go up to 3,300 m. However, Cerro Barajas, at 26°24′N 106°5′W, may be as high as 3,300 m although other sources give 3,170 m as the elevation. Cerro Gordo, at 23°12′N 104°57′W, may have an elevation between 3,350 m and 3,340 m; the southern end of the mountains may be referred to as the Sierra Huichola. In this area, the Sierra Madre begins to give way to the range province. Subranges of this area include the Sierra Pajaritos, both in Nayarit; the mountains act as a source of water, in an otherwise arid environment from the increased precipitation from the mountain range. As such, rivers that have headwaters in the mountains provide water for irrigation in the surrounding lands; the need for water to irrigate prompted the construction of dams, the source of several environmental concerns in the area.
The northern end of the range is more arid. The Yaqui drains into the Gulf of California, as do the Humaya River in Sinaloa and the Fuerte River further south; the Río Grande de Santiago drains 100,000 km2 from the southern slopes of the Sierra Madre. Along the more arid eastern slopes of the mountains, the Nazas River and Aguanaval River drain the mountains into a closed basin; these mountains supply 90% of the water used for irrigation within the watershed. North of this system is the Conchos River. Along many rivers the arid conditions have caused courses to be dammed to provide water for irrigation; these dams have caused concerns along with those caused by other activities. The Yaqui has been dammed with three large reservoirs along its course; the Río Grande de Santiago has been dammed, including the Aguamilpa dam begun in 1991 and the El Cajón Dam upstream from it. To provide irrigation water for farming the dry basin, the Nazas river was dammed in the 1930s and 1940s; this has led to the former drainage lakes in the area drying up, soil depletion from the eliminat
The Transvolcanic jay is a medium-large passerine bird similar in size to most other jays, with a blue head, blue-gray mantle, blue wings and tail, gray breast and underparts. The sexes are morphologically similar, juveniles differ only in having less blue coloration; the iris is brown and legs are black. It is most distinguished by the plain throat and breast, the mantle contrasting less with the head and wings. A 2011 decision by the American Ornithologists' Union Check-list Committee treats some populations of the Mexican jay as a separate species, called the Transvolcanic jay, based on diagnosable phenotypic differences in plumage and morphology, millions of years of genetic divergence, no evidence for interbreeding with Mexican Jays; the Transvolcanic jay inhabits montane forest in the Transvolcanic Belt of central Mexico. Populations to the north retained the common name Mexican jay, but their Latin name changed to A. wollweberi because the Transvolcanic jay is the original A. ultramarina.
Chesser, R. Terry, Richard C. Banks, F. Keith Barker, Carla Cicero, Jon L. Dunn, Andrew W. Kratter, Irby J. Lovette, Pamela C. Rasmussen, J. V. Remsen, James D. Rising, Douglas F. Stotz, Kevin Winker. 2011. Fifty-second supplement to the American Ornithologists' Union Check-List of North American Birds. Auk 128:600-613
California is a state in the Pacific Region of the United States. With 39.6 million residents, California is the most populous U. S. the third-largest by area. The state capital is Sacramento; the Greater Los Angeles Area and the San Francisco Bay Area are the nation's second and fifth most populous urban regions, with 18.7 million and 9.7 million residents respectively. Los Angeles is California's most populous city, the country's second most populous, after New York City. California has the nation's most populous county, Los Angeles County, its largest county by area, San Bernardino County; the City and County of San Francisco is both the country's second-most densely populated major city after New York City and the fifth-most densely populated county, behind only four of the five New York City boroughs. California's $3.0 trillion economy is larger than that of any other state, larger than those of Texas and Florida combined, the largest sub-national economy in the world. If it were a country, California would be the 5th largest economy in the world, the 36th most populous as of 2017.
The Greater Los Angeles Area and the San Francisco Bay Area are the nation's second- and third-largest urban economies, after the New York metropolitan area. The San Francisco Bay Area PSA had the nation's highest GDP per capita in 2017 among large PSAs, is home to three of the world's ten largest companies by market capitalization and four of the world's ten richest people. California is considered a global trendsetter in popular culture, innovation and politics, it is considered the origin of the American film industry, the hippie counterculture, fast food, the Internet, the personal computer, among others. The San Francisco Bay Area and the Greater Los Angeles Area are seen as global centers of the technology and entertainment industries, respectively. California has a diverse economy: 58% of the state's economy is centered on finance, real estate services and professional, scientific and technical business services. Although it accounts for only 1.5% of the state's economy, California's agriculture industry has the highest output of any U.
S. state. California is bordered by Oregon to the north and Arizona to the east, the Mexican state of Baja California to the south; the state's diverse geography ranges from the Pacific Coast in the west to the Sierra Nevada mountain range in the east, from the redwood–Douglas fir forests in the northwest to the Mojave Desert in the southeast. The Central Valley, a major agricultural area, dominates the state's center. Although California is well-known for its warm Mediterranean climate, the large size of the state results in climates that vary from moist temperate rainforest in the north to arid desert in the interior, as well as snowy alpine in the mountains. Over time and wildfires have become more pervasive features. What is now California was first settled by various Native Californian tribes before being explored by a number of European expeditions during the 16th and 17th centuries; the Spanish Empire claimed it as part of Alta California in their New Spain colony. The area became a part of Mexico in 1821 following its successful war for independence but was ceded to the United States in 1848 after the Mexican–American War.
The western portion of Alta California was organized and admitted as the 31st state on September 9, 1850. The California Gold Rush starting in 1848 led to dramatic social and demographic changes, with large-scale emigration from the east and abroad with an accompanying economic boom; the word California referred to the Baja California Peninsula of Mexico. The name derived from the mythical island California in the fictional story of Queen Calafia, as recorded in a 1510 work The Adventures of Esplandián by Garci Rodríguez de Montalvo; this work was the fifth in a popular Spanish chivalric romance series that began with Amadis de Gaula. Queen Calafia's kingdom was said to be a remote land rich in gold and pearls, inhabited by beautiful black women who wore gold armor and lived like Amazons, as well as griffins and other strange beasts. In the fictional paradise, the ruler Queen Calafia fought alongside Muslims and her name may have been chosen to echo the title of a Muslim leader, the Caliph. It's possible.
Know ye that at the right hand of the Indies there is an island called California close to that part of the Terrestrial Paradise, inhabited by black women without a single man among them, they lived in the manner of Amazons. They were robust of body with great virtue; the island itself is one of the wildest in the world on account of the craggy rocks. Shortened forms of the state's name include CA, Cal. Calif. and US-CA. Settled by successive waves of arrivals during the last 10,000 years, California was one of the most culturally and linguistically diverse areas in pre-Columbian North America. Various estimates of the native population range from 100,000 to 300,000; the Indigenous peoples of California included more than 70 distinct groups of Native Americans, ranging from large, settled populations living on the coast to groups in the interior. California groups were diverse in their political organization with bands, villages, on the resource-rich coasts, large chiefdoms, such as the Chumash and Salinan.
Trade, intermarriage a
Trans-Mexican Volcanic Belt
The Trans-Mexican Volcanic Belt known as the Transvolcanic Belt and locally as the Sierra Nevada, is a volcanic belt that covers central-southern Mexico. Several of its highest peaks have snow all year long, during clear weather, they are visible to a large percentage of those who live on the many high plateaus from which these volcanoes rise; the Trans-Mexican Volcanic Belt spans across Central-Southern Mexico from the Pacific Ocean to the Gulf of Mexico between 18°30'N and 21°30'N, resting on the southern edge of the North American Plate. This 1000 kilometer long, 90–230 km broad structure is an east-west, continental volcanic arc. Over several million years, the subduction of the Rivera and Cocos plates beneath the North American Plate 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. 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. These features are related to the reactivation of early fault systems during the Trans-Mexican Volcanic belt's evolution; the main brittle fault system's geometry 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 complexes, major calderas. Prior to the formation of the Trans-Mexican Volcanic Belt, Robby F an older, but related volcanic belt, the Sierra Madre Occidental occupied the area. Resuming in the Eocene, post-Laramide deformation, subduction related volcanism formed the Sierra Madre Occidental silic volcanic arc at a paleo-subduction zone off the coast of Baja California, before the peninsula rifted away. From the ocene 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 to more mafic compositions was complete, 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 basement is heterogeneous; the Trans-Mexican Volcanic Belt east of 101°W rests upon Precambrian terranes, assembled into the Oaxaquia microcontinent and on the Paleozoic Mixteco terrane. West of 101°W, the Trans-Mexican Volcanic Belt resides on top of the Guerro composite terrane - a make up of Jurassic to Cretaceous marine marginal arcs, which are built on Triassic - 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; the subducting plates originated from the breakup of the Farallon Plate at 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 Tamayo fracture zone, the Middle American Trench; the larger Cocos Plate is bordered by the North American Plate and the Caribbean Plate to the northeast, the Pacific Plate to the west, to the south by the Nazca Plate. The Cocos and Rivera are young oceanic plates that are subducting along the Middle American Trench at different convergence rates. 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 rich rocks, adakites are associated with the area. Middle Miocene adakitic rocks are found furthest from the trench and along the volcanic front of the central Trans-Mexican Volcanic Belt during the Pliocene-Quaternary, 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.
1) 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 to the Palma Sola area. 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, slab melting began to occur—suggesting flattening of the subducted slab; the oldest rocks of this age may be exposed in Central Mexico. 2) A Late Miocene ~11 Ma eastward traveling pulse of mafic volcanism swept across the whole of Central Mexico, north of the 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