An oak is a tree or shrub in the genus Quercus of the beech family, Fagaceae. There are 600 extant species of oaks; the common name "oak" appears in the names of species in related genera, notably Lithocarpus, as well as in those of unrelated species such as Grevillea robusta and the Casuarinaceae. The genus Quercus is native to the Northern Hemisphere, includes deciduous and evergreen species extending from cool temperate to tropical latitudes in the Americas, Asia and North Africa. North America contains the largest number of oak species, with 90 occurring in the United States, while Mexico has 160 species of which 109 are endemic; the second greatest center of oak diversity is China, which contains 100 species. Oaks have spirally arranged leaves, with lobate margins in many species. Many deciduous species are marcescent. In spring, a single oak tree produces small female flowers; the fruit is a nut called an oak nut borne in a cup-like structure known as a cupule. The acorns and leaves contain tannic acid, which helps to guard from insects.
The live oaks are distinguished for being evergreen, but are not a distinct group and instead are dispersed across the genus. The oak tree is a flowering plant. Oaks may be divided into two genera and a number of sections: The genus Quercus is divided into the following sections: Sect. Quercus, the white oaks of Europe and North America. Styles are short; the leaves lack a bristle on their lobe tips, which are rounded. The type species is Quercus robur. Sect. Mesobalanus, Hungarian oak and its relatives of Europe and Asia. Styles long; the section Mesobalanus is related to section Quercus and sometimes included in it. Sect. Cerris, the Turkey oak and its relatives of Europe and Asia. Styles long; the inside of the acorn's shell is hairless. Its leaves have sharp lobe tips, with bristles at the lobe tip. Sect. Protobalanus, the canyon live oak and its relatives, in southwest United States and northwest Mexico. Styles short, acorns mature in 18 months and taste bitter; the inside of the acorn shell appears woolly.
Leaves have sharp lobe tips, with bristles at the lobe tip. Sect. Lobatae, the red oaks of North America, Central America and northern South America. Styles long; the inside of the acorn shell appears woolly. The actual nut is encased in a thin, papery skin. Leaves have sharp lobe tips, with spiny bristles at the lobe; the ring-cupped oaks of eastern and southeastern Asia. Evergreen trees growing 10–40 m tall, they are distinct from subgenus Quercus in that they have acorns with distinctive cups bearing concrescent rings of scales. IUCN, ITIS, Encyclopedia of Life and Flora of China treats Cyclobalanopsis as a distinct genus, but some taxonomists consider it a subgenus of Quercus, it contains about 150 species. Species of Cyclobalanopsis are common in the evergreen subtropical laurel forests which extend from southern Japan, southern Korea, Taiwan across southern China and northern Indochina to the eastern Himalayas, in association with trees of genus Castanopsis and the laurel family. Interspecific hybridization is quite common among oaks but between species within the same section only and most common in the white oak group.
Inter-section hybrids, except between species of sections Mesobalanus, are unknown. Recent systematic studies appear to confirm a high tendency of Quercus species to hybridize because of a combination of factors. White oaks are unable to discriminate against pollination by other species in the same section; because they are wind pollinated and they have weak internal barriers to hybridization, hybridization produces functional seeds and fertile hybrid offspring. Ecological stresses near habitat margins, can cause a breakdown of mate recognition as well as a reduction of male function in one parent species. Frequent hybridization among oaks has consequences for oak populations around the world. Frequent hybridization and high levels of introgression have caused different species in the same populations to share up to 50% of their genetic information. Having high rates of hybridization and introgression produces genetic data that does not differentiate between two morphologically distinct species, but instead differentiates populations.
Numerous hypotheses have been proposed to explain how oak species are able to remain morphologically and ecologically distinct with such high levels of gene flow, but the phenomenon is still a mystery to botanists. The Fagaceae, or beech family, to which the oaks belong, is a slow evolving clade compared to other angiosperms, the patterns of hybridization and introgression in Quercus pose a gre
The sacred fir or Abies religiosa is a fir native to the mountains of central and southern Mexico and western Guatemala. It grows at high altitudes of 2,100–4,100 metres in cloud forests with cool, humid summers and dry winters in most of its habitat regime. In the state of Veracruz, it grows with precipitation all year long; the tree is resistant to regular winter snowfalls. The Spanish name "oyamel" comes from the Nahuatl word oyametl, it is called "árbol de Navidad" in Mexico. The English name derives from the binomial Abies religiosa "religious fir"; this comes from the use of its cut foliage in religious festivals in Mexico, notably at Christmas. Abies religiosa is a medium-sized to large evergreen coniferous tree growing to 25–50 m tall with a trunk diameter of up to 2 metres; the leaves are needle-like, flattened, 1.5–3.5 cm long and 1.5 mm wide by 0.5 mm thick, dark green above, with two blue-white bands of stomata below. The leaf arrangement is spiral on the shoot, but with each leaf variably twisted at the base so they lie flat to either side of and above the shoot, with none below the shoot.
The shoots are hairless or with scattered pubescence. The cones are dark blue-purple before maturity; the winged seeds are released when the cones disintegrate at maturity about 7–9 months after pollination. Trees from the western end of the range on Nevado de Colima, Jalisco have cones with larger, reflexed bract scales; the sacred fir is the preferred tree for the monarch butterfly to reside in colonies during its hibernation in the forests of the Trans-Mexican Volcanic Belt. Although monarch butterflies are known in other parts of the southern Mexican highlands as some specimens do not migrate, the bulk of them gather in a few protected fir forests near the towns of Angangueo and Avándaro, from December to March; the wood of the sacred fir is rather soft and thus not suited for woodworking. Nonetheless, its distribution is decreasing because of logging for fuel and other human-related disturbances. Liu, T. S.. A Monograph of the genus Abies. National Taiwan University
The monsoon season is the time of year when most of a region's average annual rainfall occurs. The season lasts at least a month; the term "green season" is sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the subtropics. Under the Köppen climate classification, for tropical climates, a wet season month is defined as a month where average precipitation is 60 millimetres or more. In contrast to areas with savanna climates and monsoon regimes, Mediterranean climates have wet winters and dry summers. Dry and rainy months are characteristic of tropical seasonal forests: in contrast to tropical rainforests, which do not have dry or wet seasons, since their rainfall is distributed throughout the year; some areas with pronounced rainy seasons will see a break in rainfall mid-season, when the intertropical convergence zone or monsoon trough moves to higher latitudes in the middle of the warm season. When the wet season occurs during a warm season, or summer, precipitation falls during the late afternoon and early evening.
In the wet season, air quality improves, fresh water quality improves, vegetation grows leading to crop yields late in the season. Rivers overflow their banks, some animals retreat to higher ground. Soil nutrients erosion increases; the incidence of malaria increases in areas where the rainy season coincides with high temperatures in tropical areas. Some animals have survival strategies for the wet season; the previous dry season leads to food shortages in the wet season, as the crops have yet to mature. In areas where the heavy rainfall is associated with a wind shift, the wet season is known as the monsoon. Rainfall in the wet season is due to daytime heating which leads to diurnal thunderstorm activity within a pre-existing moist airmass, so the rain falls in late afternoon and early evening in savannah and monsoon regions. Further, much of the total rainfall each day occurs in the first minutes of the downpour, before the storms mature into their stratiform stage. Most places have only one wet season, but areas of the tropics can have two wet seasons, because the monsoon trough, or Intertropical Convergence Zone, can pass over locations in the tropics twice per year.
However, since rain forests have rainfall spread evenly through the year, they do not have a wet season. It is different for places with a Mediterranean climate. In the western United States, during the cold season from September–May, extratropical cyclones from the Pacific Ocean move inland into the region due to a southward migration of the jet stream during the cold season; this shift in the jet stream brings much of the annual precipitation to the region, sometimes brings heavy rain and strong low pressure systems. The peninsula of Italy has weather similar to the western United States in this regard. Areas with a savanna climate in Sub-Saharan Africa, such as Ghana, Burkina Faso, Eritrea and Botswana have a distinct rainy season. Within the savanna climate regime and South Texas have a rainy season. Monsoon regions include the Indian subcontinent, Southeast Asia, northern sections of Australia's North, Central America and southern Mexico, the Desert Southwest of the United States, southern Guyana, portions of northeast Brazil.
Northern Guyana has the other in early winter. In western Africa, there are two rainy seasons across southern sections, but only one across the north. Within the Mediterranean climate regime, the west coast of the United States and the Mediterranean coastline of Italy and Turkey experience a wet season in the winter months; the wet season in the Negev desert of Israel extends from October through May. At the boundary between the Mediterranean and monsoon climates lies the Sonoran desert, which receives the two rainy seasons associated with each climate regime; the wet season is known by many different local names throughout the world. For example, in Mexico it is known as "storm season". Different names are given to the various short "seasons" of the year by the Aboriginal tribes of Northern Australia: the wet season experienced there from December to March is called Gudjewg; the precise meaning of the word is disputed, although it is accepted to relate to the severe thunderstorms and abundant vegetation growth experienced at this time.
In tropical areas, when the monsoon arrives, high daytime high temperatures drop and overnight low temperatures increase, thus reducing diurnal temperature variation. During the wet season, a combination of heavy rainfall and, in some places such as Hong Kong, an onshore wind, improve air quality. In Brazil, the wet season is correlated with weaker trade winds off the ocean; the pH level of water becomes more balanced due to the charging of local aquifers during the wet season. Water softens, as the concentration of dissolved materials reduces during the rainy season. Erosion is increased during rainy periods. Arroyos that are dry at other times of the year fill with runoff, in some cases with water as deep as 10 feet. Leaching of soils during periods of heavy rainfall depletes nutrients; the higher runoff from land masses affects nearby ocean areas, which are more stratified, or less mixed, due to stronger surface currents forced by the heavy rainfall runoff. High rainfall can cause widespread flooding, which can lead to landslides and mudflows in mountainous areas.
Such floods cause rivers to submerge homes. The Ghaggar-Hakra River, which only flows during India's monsoon season, can flood and damage local
Spanish conquest of the Aztec Empire
The Spanish conquest of the Aztec Empire, or the Spanish–Mexica War, was the conquest of the Aztec Empire by the Spanish Empire within the context of the Spanish colonization of the Americas. There are multiple 16th-century narratives of the events by Spanish conquerors, their indigenous allies and the defeated Aztecs, it was not a contest between a small contingent of Spaniards defeating the Aztec Empire but rather the creation of a coalition of Spanish invaders with tributaries to the Aztecs, most the Aztecs' indigenous enemies and rivals. They combined forces to defeat the Mexica of Tenochtitlan over a two-year period. For the Spanish, the expedition to Mexico was part of a project of Spanish colonization of the New World after twenty-five years of permanent Spanish settlement and further exploration in the Caribbean. Following an earlier expedition led by Juan de Grijalva to Yucatán in 1517, Spanish settler, Hernán Cortés, led an expedition to Mexico. Two years in 1519, Cortés and his retinue set sail from Cuba for Mexico.
The Spanish campaign against the Aztec Empire had its final victory on August 13, 1521, when a coalition army of Spanish forces and native Tlaxcalan warriors led by Cortés and Xicotencatl the Younger captured the emperor Cuauhtemoc and Tenochtitlan, the capital of the Aztec Empire. The fall of Tenochtitlan marks the beginning of Spanish rule in central Mexico, they established their capital of Mexico City on the ruins of Tenochtitlan. Cortés made alliances with tributaries city-states of the Aztec Empire as well as their political rivals the Tlaxcalteca and Texcocans, a former partner in the Aztec Triple Alliance. Other city-states joined, including Cempoala and Huexotzinco and polities bordering Lake Texcoco, the inland lake system of the Valley of Mexico. Important to the Spanish success was a multilingual indigenous slave woman, known to the Spanish conquistadors as Doña Marina, as La Malinche. After eight months of battles and negotiations, which overcame the diplomatic resistance of the Aztec Emperor Moctezuma II to his visit, Cortés arrived in Tenochtitlan on November 8, 1519, where he took up residence with fellow Spaniards and their indigenous allies.
When news reached Cortés of the death of several of his men during the Aztec attack on the Totonacs in Veracruz, he took Moctezuma captive, along with Cuitláhuac, his kinsman. Capturing the cacique or indigenous ruler was standard operating procedure for Spaniards in their expansion in the Caribbean, so capturing Moctezuma had considerable precedent; when Cortés left Tenochtitlan to return to the coast and deal with the expedition of Pánfilo de Narváez, sent to rein in Cortés's expedition that had exceeded its specified limits, Cortés's right-hand man Pedro de Alvarado was left in charge. Alvarado allowed a significant Aztec feast to be celebrated in Tenochtitlan and on the pattern of the earlier massacre in Cholula, closed off the square and massacred the celebrating Aztec noblemen; the official biography of Cortés by Francisco López de Gómara contains a description of the massacre. The Alvarado massacre at the Main Temple of Tenochtitlan precipitated rebellion by the population of the city.
Moctezuma was killed. According to one account, when Moctezuma, now seen by the population as a mere puppet of the invading Spaniards, attempted to calm the outraged populace, he was killed by a projectile. According to an indigenous account, the Spanish killed Moctezuma. Cortés had returned to Tenochtitlan and his men fled the capital city during the Noche Triste in June 1520; the Spanish and reinforcements returned a year on August 13, 1521 to a civilization, weakened by famine and smallpox. This made it easier to conquer the remaining Aztecs. Many of those on the Cortés expedition of 1519 had never seen combat before, including Cortés. A whole generation of Spaniards participated in expeditions in the Caribbean and Tierra Firme, learning strategy and tactics of successful enterprises; the Spanish conquest of Mexico had antecedents with established practices. The fall of the Aztec Empire was the key event in the formation of the Spanish Empire overseas, with New Spain, which became Mexico. Historical sources for the conquest of Mexico recount some of the same events in both Spanish and indigenous sources.
Others, are unique to a particular primary source or group narrating the event. Individuals and groups laud their own accomplishments, while denigrating or ignoring those of their opponents or their allies or both. 1428 – Creation of the Triple Alliance of Tenochtitlan and Tlacopan 1492-3 – Columbus reaches the Caribbean. One of the enslaved Nahua woman (known as La Malinche, Doña Marina
A summit is a point on a surface, higher in elevation than all points adjacent to it. The topographic terms acme, apex and zenith are synonymous; the term top is used only for a mountain peak, located at some distance from the nearest point of higher elevation. For example, a big massive rock next to the main summit of a mountain is not considered a summit. Summits near a higher peak, with some prominence or isolation, but not reaching a certain cutoff value for the quantities, are considered subsummits of the higher peak, are considered part of the same mountain. A pyramidal peak is an exaggerated form produced by ice erosion of a mountain top. Summit may refer to the highest point along a line, trail, or route; the highest summit in the world is Everest with height of 8844.43 m above sea level. The first official ascent was made by Sir Edmund Hillary, they reached the mountain`s peak in 1953. Whether a highest point is classified as a summit, a sub peak or a separate mountain is subjective; the UIAA definition of a peak is.
Otherwise, it's a subpeak. In many parts of the western United States, the term summit refers to the highest point along a road, highway, or railroad. For example, the highest point along Interstate 80 in California is referred to as Donner Summit and the highest point on Interstate 5 is Siskiyou Mountain Summit. A summit climbing differs from the common mountaineering. Summit expedition requires: 1+ year of training, a good physical shape, a special gear. Although a huge part of climber’s stuff can be left and taken at the base camps or given to porters, there is a long list of personal equipment. In addition to common mountaineers’ gear, Summit climbers need to take Diamox and bottles of oxygen. There are special requirements for crampons, ice axe, rappel device, etc. Geoid Hill – Landform that extends above the surrounding terrain Nadir Summit accordance Peak finder Summit Climbing Gear List
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
A mountain range or hill range is a series of mountains or hills ranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form and alignment that have arisen from the same cause an orogeny. Mountain ranges are formed by a variety of geological processes, but most of the significant ones on Earth are the result of plate tectonics. Mountain ranges are found on many planetary mass objects in the Solar System and are a feature of most terrestrial planets. Mountain ranges are segmented by highlands or mountain passes and valleys. Individual mountains within the same mountain range do not have the same geologic structure or petrology, they may be a mix of different orogenic expressions and terranes, for example thrust sheets, uplifted blocks, fold mountains, volcanic landforms resulting in a variety of rock types. Most geologically young mountain ranges on the Earth's land surface are associated with either the Pacific Ring of Fire or the Alpide Belt.
The Pacific Ring of Fire includes the Andes of South America, extends through the North American Cordillera along the Pacific Coast, the Aleutian Range, on through Kamchatka, Taiwan, the Philippines, Papua New Guinea, to New Zealand. The Andes is 7,000 kilometres long and is considered the world's longest mountain system; the Alpide belt includes Indonesia and Southeast Asia, through the Himalaya, Caucasus Mountains, Balkan Mountains fold mountain range, the Alps, ends in the Spanish mountains and the Atlas Mountains. The belt includes other European and Asian mountain ranges; the Himalayas contain the highest mountains in the world, including Mount Everest, 8,848 metres high and traverses the border between China and Nepal. Mountain ranges outside these two systems include the Arctic Cordillera, the Urals, the Appalachians, the Scandinavian Mountains, the Great Dividing Range, the Altai Mountains and the Hijaz Mountains. If the definition of a mountain range is stretched to include underwater mountains the Ocean Ridges form the longest continuous mountain system on Earth, with a length of 65,000 kilometres.
The mountain systems of the earth are characterized by a tree structure, where mountain ranges can contain sub-ranges. The sub-range relationship is expressed as a parent-child relationship. For example, the White Mountains of New Hampshire and the Blue Ridge Mountains are sub-ranges of the Appalachian Mountains. Equivalently, the Appalachians are the parent of the White Mountains and Blue Ridge Mountains, the White Mountains and the Blue Ridge Mountains are children of the Appalachians; the parent-child expression extends to the sub-ranges themselves: the Sandwich Range and the Presidential Range are children of the White Mountains, while the Presidential Range is parent to the Northern Presidential Range and Southern Presidential Range. The position of mountains influences climate, such as snow; when air masses move up and over mountains, the air cools producing orographic precipitation. As the air descends on the leeward side, it warms again and is drier, having been stripped of much of its moisture.
A rain shadow will affect the leeward side of a range. Mountain ranges are subjected to erosional forces which work to tear them down; the basins adjacent to an eroding mountain range are filled with sediments which are buried and turned into sedimentary rock. Erosion is at work while the mountains are being uplifted until the mountains are reduced to low hills and plains; the early Cenozoic uplift of the Rocky Mountains of Colorado provides an example. As the uplift was occurring some 10,000 feet of Mesozoic sedimentary strata were removed by erosion over the core of the mountain range and spread as sand and clays across the Great Plains to the east; this mass of rock was removed as the range was undergoing uplift. The removal of such a mass from the core of the range most caused further uplift as the region adjusted isostatically in response to the removed weight. Rivers are traditionally believed to be the principal cause of mountain range erosion, by cutting into bedrock and transporting sediment.
Computer simulation has shown that as mountain belts change from tectonically active to inactive, the rate of erosion drops because there are fewer abrasive particles in the water and fewer landslides. Mountains on other planets and natural satellites of the Solar System are isolated and formed by processes such as impacts, though there are examples of mountain ranges somewhat similar to those on Earth. Saturn's moon Titan and Pluto, in particular exhibit large mountain ranges in chains composed of ices rather than rock. Examples include the Mithrim Montes and Doom Mons on Titan, Tenzing Montes and Hillary Montes on Pluto; some terrestrial planets other than Earth exhibit rocky mountain ranges, such as Maxwell Montes on Venus taller than any on Earth and Tartarus Montes on Mars, Jupiter's moon Io has mountain ranges formed from tectonic processes including Boösaule Montes, Dorian Montes, Hi'iaka Montes and Euboea Montes. Peakbagger Ranges Home Page Bivouac.com