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60-595: The Sierras Pampeanas are a chain of mountains that rise sharply from the surrounding pampa region of Northwest Argentina. They run parallel to the Andes Mountains and their crest line is some 540 km (340 mi) east of the Andes crest line (running from 29° to 35° S latitude at about 65° W longitude). They cross into seven Argentina provinces: San Luis , San Juan , Córdoba , La Rioja , Catamarca , Santiago del Estero and Tucumán . The highest point of

120-746: A peneplain in the eastern Sierras Pampeanas. Later tectonic movements split this surface into various levels with the highest level being Pampa de Achala . As the South Atlantic opened following the Paraná-Etendeka flood basalts , the Andean orogeny began the formation of the Andes, the product of volcanism and compressional forces along the Pacific margin, but also resulted in the development of extensional basins in South America and

180-407: A terrane was accreted to the edge of the continent. Any of this material may be folded, refolded and metamorphosed. New igneous rock may freshly intrude into the crust from underneath, or may form underplating , where the new igneous rock forms a layer on the underside of the crust. The majority of continental crust on the planet is around 1 to 3 billion years old, and it is theorised that there

240-459: A weak zone on which the harder (stronger) limestone cover was able to move over the hard basement, making the distinction between basement and cover even more pronounced. In Andean geology the basement refers to the Proterozoic , Paleozoic and early Mesozoic ( Triassic to Jurassic ) rock units as the basement to the late Mesozoic and Cenozoic Andean sequences developed following

300-554: A "valley"); these are called "barreales" (mud-flats) or "pampas" (grassy plains). The Sierras Pampeanas are composed of several sub-ranges: The name "Pampean Ranges" can be misleading, since the Argentine Pampas cover most of the country's northern and eastern portion. However, other mountains which rise from these expanses are considered distinct geologic formations, not part of the Sierras Pampeanas. Before

360-406: A height of 1,300 m (4,265 ft) and 500 m (1,640 ft), respectively. The climate is temperate, with precipitation of 600 to 1,200 mm (23.6 to 47.2 in) that is more or less evenly distributed throughout the year, making the soils appropriate for agriculture . The area is also one of the distinct physiography provinces of the larger Paraná – Paraguay plain division. It

420-638: A passive margin along the Atlantic coast, processes still going on today. The basement of the Sierras Pampeanas was uplifted during the Andean orogeny over a near-horizontal segment of the subducting Nazca Plate . Sierras Pampeanas was also affected by Miocene arc magmatism 700 km (430 mi) east of the Chile Trench during this period. This region has a temperate and semi-arid climate, with warm summers and cool winters. The northern east slope

480-473: A plate of oceanic crust is subducted beneath an overriding plate of oceanic crust, as the underthrusting crust melts, it causes an upwelling of magma that can cause volcanism along the subduction front on the overriding plate. This produces an oceanic volcanic arc , like Japan . This volcanism causes metamorphism , introduces igneous intrusions , and thickens the crust by depositing additional layers of extrusive igneous rock from volcanoes. This tends to make

540-522: A relatively thin veneer, but can be more than 5 kilometres (3 mi) thick. The basement rock of the crust can be 32–48 kilometres (20–30 mi) thick or more. The basement rock can be located under layers of sedimentary rock, or be visible at the surface. Basement rock is visible, for example, at the bottom of the Grand Canyon , consisting of 1.7- to 2-billion-year-old granite ( Zoroaster Granite ) and schist ( Vishnu Schist ). The Vishnu Schist

600-594: Is believed to be highly metamorphosed igneous rocks and shale , from basalt , mud and clay laid from volcanic eruptions, and the granite is the result of magma intrusions into the Vishnu Schist. An extensive cross section of sedimentary rocks laid down on top of it through the ages is visible as well. The basement rocks of the continental crust tend to be much older than the oceanic crust. The oceanic crust can be from 0–340 million years in age, with an average age of 64 million years. Continental crust

660-836: Is considered that the limit of the Pampas plain is to the north with the Atlantic Forest and the Great Chaco Plain , to the west with the Pampas Mountains and the Cuyo Region , and to the south with Patagonia . This region has generally low elevations, whose highest levels generally do not exceed 600 metres (2,000 ft) in altitude. The coastal areas and most of the Buenos Aires Province are predominantly plain (with some wetlands ) and

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720-564: Is covered by rainforest, due to high humidity in this subtropical zone. The portions within Córdoba and San Luis enjoy Mediterranean-type climate, with intense summer rainstorms and snowy winters; the vegetation here includes conifer trees. More precipitation falls on the eastern slopes, which meet the moist winds from the Atlantic Ocean . Groundwater is not abundant in most of this area; the eastern slopes show greater population due to

780-464: Is more abundant is agricultural output destined for outside sale. Tree crops are grown in the foothills of the Sierras de Córdoba, including olives , peach , pear , apricot , fig trees , quince , lemon trees , and plantations of cypress , cedar , ponderosa pine , eucalyptus , poplar , oak , and willow which are grown for timber and forest products. Shrubs and medicinal herbs grown in

840-495: Is older because continental crust is light and thick enough so it is not subducted, while oceanic crust is periodically subducted and replaced at subduction and oceanic rifting areas. The basement rocks are often highly metamorphosed and complex, and are usually crystalline . They may consist of many different types of rock – volcanic, intrusive igneous and metamorphic. They may also contain ophiolites , which are fragments of oceanic crust that became wedged between plates when

900-470: Is the most typical landscape of the countryside areas in the northern parts of the Pampas. The highest elevations of the Pampas region are found in the Sierra de la Ventana mountains , in the southern part of Buenos Aires Province, with 1,239 metres (4,065 ft) at the summit of Cerro Tres Picos . The climate of the Pampas is generally temperate, gradually giving way to a more humid subtropical climate in

960-413: Is the thick foundation of ancient, and oldest, metamorphic and igneous rock that forms the crust of continents , often in the form of granite . Basement rock is contrasted to overlying sedimentary rocks which are laid down on top of the basement rocks after the continent was formed, such as sandstone and limestone . The sedimentary rocks which may be deposited on top of the basement usually form

1020-429: Is warmer than fall in most areas (especially in the west) but significantly colder along the Atlantic. Violent storms are more common as well as wide temperature variations: days of 35 °C (95 °F) can give way to nights of under 5 °C (41 °F) or even frost, all within only a few days. Precipitation ranges from 1,400 millimetres (55 in) in the northeast to about 400 millimetres (16 in) or less in

1080-836: The Famatinian orogeny which accreted the Precordillera Terrane to Gondwana. In the Gondwanide orogeny , Gondwana reached its maximum extent in the Early Carboniferous and began to break-up in the Early Cretaceous. Along the Pacific margin the convergence of tectonic plates lead to renewed subduction which produced the large rhyolitic provinces and plutonic belts of the Permian–Jurassic. Between 530 and 440 million years ago, during

1140-650: The Guanaco have been extirpated completely from this habitat. Mammals that are still fairly present include Brazilian guinea pig , southern mountain cavy , coypu , Pampas fox , Geoffroy's cat , lesser grison , white-eared opossum , Molina's hog-nosed skunk , big lutrine opossum , big hairy armadillo and southern long-nosed armadillo . Bird species of the pampas are ruddy-headed goose , pampas meadowlark , hudsonian godwit , maguari stork , white-faced ibis , white-winged coot , southern screamer , dot-winged crake , curve-billed reedhaunter , burrowing owl and

1200-589: The Pampas Plain , are fertile South American low grasslands that cover more than 1,200,000 square kilometres (460,000 sq mi) and include the Argentine provinces of Buenos Aires , La Pampa , Santa Fe , Entre Ríos , and Córdoba ; all of Uruguay ; and Brazil 's southernmost state , Rio Grande do Sul . The vast plains are a natural region , interrupted only by the low Ventana and Tandil hills, near Bahía Blanca and Tandil (Argentina), with

1260-597: The Pampean and Famatinian orogenies the area of the Sierras Pampeanas was intruded by a series of pegmatite dykes. Later, around 370 million years ago a smaller event of pegmatite intrusion took place. Today these dykes are collectively known as the Pampean Pegmatite Province . These pegmatites host valuable lithium reserves. By the end of the Paleozoic erosion had led to the formation of

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1320-537: The Paraná River , and includes all of Uruguay, most of Entre Ríos and Corrientes provinces in Argentina, and the southern portion of Brazil's state of Rio Grande do Sul. The Humid Pampas include eastern Buenos Aires Province, and southern Entre Ríos Province. The Semiarid Pampas includes western Buenos Aires Province and adjacent portions of Santa Fe, Córdoba, and La Pampa provinces. The Pampas are bounded by

1380-532: The viscacha and guinea pig . The observed fauna varies according to the combination of three basic natural factors: the arrangement of mountain ranges, altitude and climate. There are important variances of biome in the Pampas Sierras: semi-arid areas, rain-forest areas, and moderately fertile areas covered with natural forests (especially in Córdoba and San Luis). In the arid zone of La Rioja and Catamarca are found vicuña and some alpaca . Earlier in

1440-449: The 1840s but intensifying after the 1880s, European immigrants began to migrate to the Pampas, first as part of government-sponsored colonization schemes to settle the land and later as tenant farmers "working as either a sharecropper or as paid laborers for absentee landowners" in an attempt to make a living for themselves. However, many immigrants eventually moved to more permanent employment in cities, as industrialization picked up after

1500-516: The 1930s. As a result, Argentina's history of immigration in Buenos Aires Province is typically associated with cities and urban life, unlike in Entre Ríos Province and Santa Fe Province, where European immigration took on a more rural profile. Basement (geology) In geology , basement and crystalline basement are crystalline rocks lying above the mantle and beneath all other rocks and sediments. They are sometimes exposed at

1560-547: The Earth's continents being accreted into one giant supercontinent . Most continents, such as Asia, Africa and Europe, include several continental cratons, as they were formed by the accretion of many smaller continents. In European geology , the basement generally refers to rocks older than the Variscan orogeny . On top of this older basement Permian evaporites and Mesozoic limestones were deposited. The evaporites formed

1620-642: The Mesozoic the Sierras Pampeanas was affected by cycles of orogenic events produced by a series continent-continent collisions along the Proto-Pacific margin of Gondwana . The Neoproterozoic–Cambrian Pampean orogeny was a major event along south-western Gondwana that coincided with the end of the Brasiliano – Pan-African orogenies. In the Cambrian, subduction along the Proto-Pacific margin lead to

1680-475: The Pampas south and west of Buenos Aires . Much of the area is also used for cattle , and more recently, to cultivate vineyards in the Buenos Aires wine region . The area is also used for farming honey using European honeybees . These farming regions are particularly susceptible to flooding during thunderstorms. The weather averages out to be 16 °C (60 °F) year-round in the Pampas. Starting in

1740-500: The Pampas, but it is much more frequent in the southwest than around the Parana and Uruguay Rivers. Temperatures under −5 °C (23 °F) can occur everywhere, but values of −10 °C (14 °F) or lower are confined to the south and west. Snow almost never falls in the northernmost third and is rare and light elsewhere, except for exceptional events in which depths have reached 30 cm (12 in). Springs are very variable; it

1800-517: The Pampas: Human activity has caused major changes to the wildlife of the Pampas. Most big or medium-sized species such as puma , rhea , Capybara , plains viscacha , maned wolf , marsh deer and Pampas deer have lost their habitats especially due to the spread of agriculture and ranching , and are only present in very few relicts of the pampas. Other species, such as the Jaguar and

1860-767: The Sierra de la Ventana mountains, Argentina). Summer temperatures are more uniform than winter temperatures, generally ranging from 28 to 33 °C (82 to 91 °F) during the day. However, most cities in the Pampas occasionally have high temperatures that push 38 °C (100 °F), as occurs when warm, dry, northerly winds blow from southern Brazil, northern Argentina or Paraguay . Autumn arrives gradually in March and peaks in April and May. In April, highs range from 20 to 25 °C (68 to 77 °F) and lows from 9 to 13 °C (48 to 55 °F). The first frosts arrive in mid-April in

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1920-521: The Sierras Pampeanas is Cerro General Belgrano (6250 m above sea level) in La Rioja, in the Sierra de Famatina . Between the mountain ranges are several salt-filled depressions. The Salinas Grandes depression is located in Cordoba, La Rioja, Catamarca and Santiago del Estero. A characteristic of many of these mountain ranges is their morphological asymmetry: the western slopes are usually steeper than

1980-452: The Sierras de Córdoba include peperina , pennyroyal , dandelion , plantain , canchalagua , wild grapes , chamomile , malva , lime and passion fruit . In arid areas such as the center and west of La Rioja and Catamarca, irrigated vines thrive, and large plantations of olive trees, ( jujube was brought by Lebanese immigrants and Syrians in early twentieth century), grains , aloe and jojoba . Most of these products are sold within

2040-514: The Sierras. High-elevation Central Andean Puna grasslands occur along the ridgeline of the Sierra de Aconquija. Extant species include algarrobo blanco (white carob) , algarrobo negro , chañar , jarilla , mistol , piquillin , tala , alpataco , tabaquillo and espinillo . In the more arid regions (the west faces) grow giant or medium cactus and various shrubs ( chilca , tola , etc.) The Southern Andean Yungas are humid forests found on east-facing slopes with higher rainfall. Trees of

2100-561: The Yungas include Andean alder ( Alnus acuminata ), the conifer Podocarpus parlatorei , and deciduous trees including walnut ( Juglans australis ), jacaranda , Pisonia , Schinus molle , quebracho , acacia , and flowering plants such as orchids , jasmine and bromeliads . The Sierras de Córdoba in Córdoba and San Luis provinces have abundant vegetation on the eastern slopes, including carob, "coconuts" (local name of palm trees), garabato blanco ( acacia ) and willow . Much of

2160-432: The amount of rainy days is fairly constant. Very intense thunderstorms are common in the spring and summer, and it has among the most frequent lightning and highest convective cloud tops in the world. The severe thunderstorms produce intense hailstorms , both floods and flash floods , and the most consistently active tornado region outside the central and southeastern US. Climate charts for different locations of

2220-423: The area is deforested due to desertification , logging ( "clearing"), strip-mining (without resurfacing or replanting), animal overgrazing , and burning to open up areas for grazing. The area boasts a diverse fauna, although several species are moving toward extinction (such as the boa ). Among the native animals: puma , brocket deer (in the north), wildcat , fox , armadillo and mule deer ; rodents such as

2280-416: The crust thicker and less dense, making it immune to subduction. Oceanic crust can be subducted, while continental crust cannot. Eventually, the subduction of the underthrusting oceanic crust can bring the volcanic arc close to a continent, with which it may collide. When this happens, instead of being subducted, it is accreted to the edge of the continent and becomes part of it. Thin strips or fragments of

2340-471: The drier Argentine Espinal grasslands, which form a semicircle around the north, west, and south of the Humid Pampas. Winters are cold to mild, and summers are hot and humid. Rainfall is fairly uniform throughout the year but is a little heavier during the summer. Annual rainfall is heaviest near the coast and decreases gradually further inland. Rain during the late spring and summer usually arrives in

2400-616: The eastern slopes, thus the former are sometimes called coasts and the latter are called skirts . The narrow valleys are called "broken" or "open"; the narrow openings between valleys are called "doors". Due to erosion and other geologic forces (volcanoes, glaciers, rivers, tectonic etc.), the surface of this area varies widely. It includes cliffs and narrow channels of some rivers which are named "drawers" (if they are of moderate size) or "guns "(if they are older); there are abundant caves , grottos and overhangs. Some mountains are separated by significant open areas (too large to be considered

2460-511: The edge of the continent. There are exceptions, however, such as exotic terranes . Exotic terranes are pieces of other continents that have broken off from their original parent continent and have become accreted to a different continent. Continents can consist of several continental cratons – blocks of crust built around an initial original core of continents – that gradually grew and expanded as additional newly created terranes were added to their edges. For instance, Pangea consisted of most of

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2520-412: The form of brief heavy showers and thunderstorms. More general rainfall occurs the remainder of the year as cold fronts and storm systems move through. Although cold spells during the winter often send nighttime temperatures below freezing, snow is quite rare. In most winters, a few light snowfalls occur over inland areas. Central Argentina boasts a successful agricultural business, with crops grown on

2580-399: The greater runoff water available there. There are short, torrential rivers and many streams and rivulets that carry low flows, with brief and violent floods caused by summer rains. These rivers are used for the production of hydropower . The flora and fauna of the Sierras Pampeanas varies with elevation and exposure. The Dry Chaco , a region of dry forests, shrublands, and savannas, lies in

2640-689: The interior areas (mainly in the southern part of the Brazilian state of Rio Grande do Sul and Uruguay) have low ranges of hills (like Serras de Sudeste in Brazil and Cuchilla Grande in Uruguay). Low hills covered by grasslands are called coxilhas ( Portuguese pronunciation: [koˈʃiʎɐs] ) in Portuguese and cuchillas ( Spanish pronunciation: [kuˈtʃiʝas] ) in Spanish, and it

2700-491: The lowlands and foothills to the east. The east-facing slopes of the sierras intercept moisture-bearing winds, and are more humid than the adjacent lowlands. These higher-rainfall slopes are home to the Southern Andean Yungas humid forests. The western slopes are in the more arid rain shadow of the ranges. The High Monte shrublands are found in the western slopes and intermountain valleys and basins west of

2760-465: The north ( Cfa , according to the Köppen climate classification , with a Cwa tendency (drier winters) in the northwestern edge); a cold semi-arid climate ( BSk ) on the southern and western fringes (like San Luis Province , western La Pampa Province and southern Buenos Aires Province); and an oceanic climate ( Cfb ) in the southeastern part (in the localities of Mar del Plata , Necochea , Tandil and

2820-738: The onset of subduction along the western margin of the South American Plate . When discussing the Trans-Mexican Volcanic Belt of Mexico the basement include Proterozoic, Paleozoic and Mesozoic age rocks for the Oaxaquia, the Mixteco and the Guerrero terranes respectively. The term basement is used mostly in disciplines of geology like basin geology , sedimentology and petroleum geology in which

2880-422: The pampas are relicts of drier past climates. These explanations have been criticised as mono-causal. "Overall, we expect that low propagule pressure, abiotic stresses, biotic resistance, and a paucity of specific symbionts might have exerted a synergistic influence in slowing tree invasion rates ". The World Wildlife Fund divides the Pampas into three distinct ecoregions . The Uruguayan Savanna lies east of

2940-449: The pristine pampas were treeless regions has been much debated. Perhaps the most commonly cited explanation is seasonal drought. A related hypothesis is that grass roots compete for water and exclude tree seedlings. The effect might be increased by heavy, clayed soils which limit tap root penetration. Other causes that have been proposed are fires set by indigenous peoples for land clearance; the existence of heavy-bodied herbivores; and that

3000-424: The region have introduced domestic animals such as horses, donkeys, goats, pigs, cattle and sheep. Agriculture is the predominant economic activity in the area. Certain areas are noted for wine and olive oil production, as well as cheeses , homemade breads , pies , sweets (the best known nationally are the sweet potato and quince ) and alcohol . Most products are for local consumption. Only where rainfall

3060-499: The region, mainly associated with tourism . Due to its climate and spectacular scenery the Sierras Pampeanas are a major tourist destination in Argentina. Salt mining is an important industry; the salt beds there are the country's largest, covering some 8400 km. 32°S 65°W  /  32°S 65°W  / -32; -65 Pampa The Pampas (from the Quechua : pampa , meaning "plain"), also known as

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3120-511: The rhea. Invasive species include the European hare , wild boar and house sparrow . Most of the large mammals native to the Pampas became extinct as part of the end-Pleistocene extinction event of most large mammals across the Americas around 12,000 years ago. Notable former inhabitants of the Pampas include the giant elephant-sized ground sloth Megatherium americanum , along side

3180-426: The sabertooth cat Smilodon populator . The dominant vegetation types are grassy prairie and grass steppe , in which numerous species of the grass genus Stipa are particularly conspicuous. "Pampas grass" ( Cortaderia selloana ) is an iconic species of the Pampas. Vegetation typically includes perennial grasses and herbs . Different strata of grasses occur because of gradients of water availability. Why

3240-410: The smaller (though still large) ground sloths Mylodon , Glossotherium Lestodon and Catonyx , the rhinoceros like ungulate Toxodon , the camel-like Macrauchenia , the gomphothere (elephant-relative) Notiomastodon , the equines Equus neogeus and Hippidion , and the glyptodonts (car-sized relatives of armadillos) Glyptodon and Doedicurus , the bear Arctotherium and

3300-450: The south and late May or early June in the north. Winters are generally mild, but cold waves often occur. Typical temperatures range from 12 to 19 °C (54 to 66 °F) during the day, and from 1 to 6 °C (34 to 43 °F) at night. With strong northerly winds, days of over 25 °C (77 °F) can be recorded almost everywhere, and during cold waves, high temperatures can be only 6 °C (43 °F). Frost occurs everywhere in

3360-512: The southern and western edges. It is highly seasonal in the West, with some places recording averages of 120 millimetres (4.7 in) monthly in the summer, and only 20 millimetres (0.79 in) monthly in the winter. The eastern areas have small peaks in the fall and the spring, with relatively rainy summers and winters that are only slightly drier. However, where summer rain falls as short, heavy storms, winter rain falls mostly as cold drizzle, and so

3420-525: The surface, but often they are buried under miles of rock and sediment. The basement rocks lie below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin. In the same way, the sediments or sedimentary rocks on top of the basement can be called a "cover" or "sedimentary cover". Crustal rocks are modified several times before they become basement, and these transitions alter their composition. Basement rock

3480-413: The twentieth century jaguar were found in the rainforests. In the eighteenth century there were sightings of spectacled bears . The avifauna is diverse and relatively abundant in the higher, mostly arid areas. It includes Andean condors and vultures . In the fertile plains of Tucumán Province previously were found rhea , turkey , parrot , hummingbird , woodpecker and pigeons . Settlers to

3540-414: The underthrusting oceanic plate may also remain attached to the edge of the continent so that they are wedged and tilted between the converging plates, creating ophiolites . In this manner, continents can grow over time as new terranes are accreted to their edges, and so continents can be composed of a complex quilt of terranes of varying ages. As such, the basement rock can become younger going closer to

3600-572: Was at least one period of rapid expansion and accretion to the continents during the Precambrian. Much of the basement rock may have originally been oceanic crust, but it was highly metamorphosed and converted into continental crust . It is possible for oceanic crust to be subducted down into the Earth's mantle , at subduction fronts, where oceanic crust is being pushed down into the mantle by an overriding plate of oceanic or continental crust. When

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