80-796: The Pali-Aike volcanic field is a volcanic field along the Argentina–Chile border . It is part of a family of back-arc volcanoes in Patagonia , which formed from processes involving the collision of the Chile Ridge with the Peru–Chile Trench . It lies farther east than the Austral Volcanic Zone , the volcanic arc that makes up the Andean Volcanic Belt at this latitude. Pali-Aike formed over sedimentary rock of Magallanes Basin ,
160-470: A Jurassic-age basin starting from the late Miocene as a consequence of regional tectonic events. The volcanic field consists of an older plateau basalt formation and younger volcanic centres in the form of pyroclastic cones , scoria cones , maars and associated lava flows. There are approximately 467 vents in an area of 4,500 square kilometres (1,700 square miles). The vents often form local alignments along lineaments or faults , and there are
240-674: A sodium -rich alkaline suite; nephelinite has been reported and hawaiite is rare. The most important phenocrystic phase is olivine , which also appears as xenocrysts ; other minerals include clinopyroxene , diopside and plagioclase . The groundmass has a similar composition with the addition of augite , feldspar and magnetite and occasionally ilmenite and nepheline . Pali-Aike rocks typically feature ultramafic xenoliths containing augite, dunite , eclogite , garnet , harzburgite , lherzolite , peridotite , phlogopite , pyroxenite , spinel and wehrlites . The composition of these xenoliths indicates that they originated from both
320-582: A few volcanic centres have been investigated as possible geosites . Laguna Azul is already a provincial geosite and tourism target. The Pali-Aike National Park was created in 1970 on the Chilean side and the Laguna Azul Provincial Reserve on the Argentine side, which encompasses Laguna Azul, in 2005. Volcanic field A volcanic field or crater row is an area of Earth 's crust that
400-589: A mass extinction that began roughly 10,000 years ago, though the species becoming extinct have only been recorded since the Industrial Revolution . This is sometimes referred to as the " Sixth Extinction ". It is often cited that over 322 recorded species have become extinct due to human activity since the Industrial Revolution, but the rate may be as high as 500 vertebrate species alone, the majority of which have occurred after 1900. Geologically ,
480-485: A number of maars and other lakes, both volcanic and non-volcanic. The volcanic field is noteworthy for the presence of large amounts of xenoliths in its rocks and because the maar Potrok Aike is located here, where palaeoclimate data have been obtained. The field was active starting from 3.78 million years ago. The latest eruptions occurred during the Holocene , as indicated by the burial of archaeological artifacts;
560-762: A rate of 2 centimetres per year (0.79 in/year) in the Peru–Chile Trench. This subduction process has caused adakitic volcanism on the western margin of southernmost South America, forming the Austral Volcanic Zone. Patagonia is a region where four tectonic plates , the Antarctic Plate, the Nazca Plate , the Scotia Plate and the South America Plate , interact. Starting 4 million years ago
640-591: A role of the Bouvet hotspot of the Atlantic in generating them has been discussed. The basement beneath Pali-Aike contains the Magallanes Basin of Jurassic age, which formed during the breakup of Gondwana and was later filled by volcanic and sedimentary rocks. The mantle underneath Pali-Aike is up to 2.5 billion years old. The partly Neoproterozoic Deseado Massif lies north of Pali-Aike and may extend beneath
720-508: A southward migration or a northeastward one in the case of the plateau lavas, following the movement of the triple junction to the north; in that case Pali-Aike would be an exception, probably due to local tectonic effects. However, some older plateau lavas in the north formed in response to an earlier ridge subduction event in the Eocene and Palaeocene . The actual Andean volcanic arc is located 300 kilometres (190 mi) west of Pali-Aike, in
800-571: A trend of desiccation which resulted in the creation of the Sahara , Namib , and Kalahari deserts. Many animals evolved including mammoths , giant ground sloths , dire wolves , sabre-toothed cats, and Homo sapiens . 100,000 years ago marked the end of one of the worst droughts in Africa, and led to the expansion of primitive humans. As the Pleistocene drew to a close, a major extinction wiped out much of
880-454: A very important role in this era, shaping the evolution of the birds and mammals that fed on them. One group that diversified significantly in the Cenozoic as well were the snakes . Evolving in the Cenozoic, the variety of snakes increased tremendously, resulting in many colubrids , following the evolution of their current primary prey source, the rodents . In the earlier part of the Cenozoic,
SECTION 10
#1732843996698960-699: A volcanic field's vents have their own source of magma, possibly of different compositions (such as basalt and rhyolite ), and these vents may span an area of thousands of square miles. Scoria cones are particularly prone to cluster into volcanic fields, which are typically 30–80 kilometers (19–50 miles) in diameter and consist of several tens to several hundred individual cones. The unusually large Trans-Mexican Volcanic Belt has nearly 1000 cones covering an area of 60,000 square kilometers (23,000 sq mi). Cenozoic The Cenozoic ( / ˌ s iː n ə ˈ z oʊ . ɪ k , ˌ s ɛ n -/ SEE -nə- ZOH -ik, SEN -ə- ; lit. ' new life ' )
1040-528: Is 240,000 years before present. The youngest vent is Diablo Negro-La Morada del Diablo along the Chile-Argentina border, which covered an area of 100 square kilometres (39 sq mi) with lava. Volcanic deposits have covered archaeological artifacts at the Pali-Aike Cave, indicating volcanic activity between 10,000 and 5,000 years before present and within the last 15,000 years;
1120-595: Is Earth's current geological era , representing the last 66 million years of Earth's history. It is characterized by the dominance of mammals , birds , conifers , and angiosperms (flowering plants). It is the latest of three geological eras of the Phanerozoic Eon , preceded by the Mesozoic and Paleozoic . The Cenozoic started with the Cretaceous–Paleogene extinction event , when many species, including
1200-483: Is a period in which grasses spread further, dominating a large portion of the world, at the expense of forests. Kelp forests evolved, encouraging the evolution of new species, such as sea otters . During this time, perissodactyla thrived, and evolved into many different varieties. Apes evolved into 30 species. The Tethys Sea finally closed with the creation of the Arabian Peninsula , leaving only remnants as
1280-409: Is formed by a plateau of lava flows that is up to 120 metres (390 ft) thick (in its northwestern reach), with an average relief of 20–100 metres (66–328 ft). This plateau is formed by tables containing depressions and lakes, and whose margins are steep-dipping slopes that accumulate blocks at their feet. It includes remnants of individual volcanic centres, and some volcanic necks situated in
1360-449: Is in the commune of San Gregorio, Chile . The cities of Rio Gallegos (Argentina) and Punta Arenas (Chile) lie northeast and southwest of Pali-Aike respectively. Unusually for Argentine volcanoes, Pali-Aike volcanoes are close to urban areas since the closest vent is only 23 kilometres (14 mi) or 30 kilometres (19 mi) away from Rio Gallegos; the vents are easily observed from the city. The Monte Aymond border pass lies next to
1440-499: Is much larger (crater diameter of 5 kilometres (3.1 mi)); its rim is barely recognizable and appears to be more akin to a maar. Laguna Timone is surrounded by a 2 kilometres (1.2 mi) wide tuff ring and is among the largest maars in the Pali-Aike volcanic field, although the lake covers only part of the maar depression. Additional maars in the southwestern part of the field are the so-called "West Maar" and "East Maar", which contain
1520-540: Is no trace of geochemical influence of the adjacent Andean Volcanic Belt and the associated subduction zone. An older oceanic lithosphere that was emplaced during the Proterozoic - Palaeozoic in the area is also involved in magma genesis. The various isotope ratios are typical for so-called " cratonic " Patagonian back-arc basalts that are remote from the Andean Volcanic Belt and resemble ocean island basalts ;
1600-448: Is prone to localized volcanic activity. The type and number of volcanoes required to be called a "field" is not well-defined. Volcanic fields usually consist of clusters of up to 100 volcanoes such as cinder cones . Lava flows may also occur. They may occur as a monogenetic volcanic field or a polygenetic volcanic field . Alexander von Humboldt observed in 1823 that geologically young volcanoes are not distributed uniformly across
1680-524: Is the southernmost and youngest lava plateau in Patagonia. Their activity began 16 million years ago, when the Chile Ridge collided with the Peru–Chile Trench and thus caused a tear in the subducting slab and the formation of a slab window beneath Patagonia. Another theory is that slab rollback might instead be the mechanism by which volcanism is triggered in the Pali-Aike region. The age trends of volcanism have been interpreted as indicating either
SECTION 20
#17328439966981760-526: The Black , Red , Mediterranean and Caspian Seas . This increased aridity. Many new plants evolved: 95% of modern seed plants families were present by the end of the Miocene. The Pliocene Epoch lasted from 5.333 to 2.58 million years ago. The Pliocene featured dramatic climatic changes, which ultimately led to modern species of flora and fauna. The Mediterranean Sea dried up for several million years (because
1840-474: The Global Volcanism Program mentions a 5,550 ± 2,500 BCE eruption. Sediment cores from Laguna Azul give an approximate age of 3,400 years before present , suggesting that this vent formed during the late Holocene. Tephra deposits in the region may have originated at Pali-Aike. The volcanic field was rated Argentina's 18th (out of 38) most dangerous volcano in a 2016 study. The climate in
1920-681: The Isthmus of Panama around 2.8 million years ago , the Arctic region cooled due to the strengthening of the Humboldt and Gulf Stream currents, eventually leading to the glaciations of the Quaternary ice age , the current interglacial of which is the Holocene Epoch. Recent analysis of the geomagnetic reversal frequency, oxygen isotope record, and tectonic plate subduction rate, which are indicators of
2000-843: The K-Pg event , the planet was dominated by relatively small fauna, including small mammals, birds, reptiles, and amphibians. From a geological perspective, it did not take long for mammals to greatly diversify in the absence of the dinosaurs that had dominated during the Mesozoic. Birds also diversified rapidly; some flightless birds grew larger than humans. These species are sometimes referred to as " terror birds ", and were formidable predators. Mammals came to occupy almost every available niche (both marine and terrestrial ), and some also grew very large, attaining sizes not seen in most of today's terrestrial mammals. The ranges of many Cenozoic bird clades were governed by latitude and temperature and have contracted over
2080-561: The K–Pg extinction event included the extinction of large herbivores , which permitted the spread of dense but usually species-poor forests. The Early Paleocene saw the recovery of Earth. The continents began to take their modern shape, but all the continents and the subcontinent of India were separated from each other. Afro-Eurasia was separated by the Tethys Sea , and the Americas were separated by
2160-575: The Quaternary glaciation dried and cooled Earth. Cenozoic derives from the Greek words kainós ( καινός 'new') and zōḗ ( ζωή 'life'). The name was proposed in 1840 by the British geologist John Phillips (1800–1874), who originally spelled it Kainozoic . The era is also known as the Cænozoic , Caenozoic , or Cainozoic ( / ˌ k aɪ . n ə ˈ z oʊ . ɪ k , ˌ k eɪ -/ ). In name,
2240-574: The Tehuelche language , where pale means "hunger" and aike means "location". Originally it was the name of a farm ( estancia ) and was later applied to the volcanic field. The Pali-Aike volcanic field spans the border between Argentina and Chile, northwest of the Magellanes Strait . Most of the field lies in Argentina within the southernmost part of Santa Cruz Province , while the Chilean part
2320-431: The crust and the mantle . In addition, rocks from Pali-Aike contain inclusions of fluids consisting of carbon dioxide . Some rocks have been weathered and form palagonite . Elemental composition is typical for alkaline intraplate basalts. The geochemistry of Pali-Aike rocks has been interpreted as originating from the melting of peridotite in the mantle along with fractionation of olivine and with residual garnet; there
2400-608: The ice ages reduced sea levels, disconnecting the Atlantic from the Mediterranean, and evaporation rates exceeded inflow from rivers). Australopithecus evolved in Africa , beginning the human branch. The isthmus of Panama formed, and animals migrated between North and South America during the great American interchange , wreaking havoc on local ecologies. Climatic changes brought: savannas that are still continuing to spread across
2480-733: The isthmus of Panama . India collided with Asia 55 to 45 million years ago creating the Himalayas; Arabia collided with Eurasia, closing the Tethys Ocean and creating the Zagros Mountains , around 35 million years ago . The break-up of Gondwana in Late Cretaceous and Cenozoic times led to a shift in the river courses of various large African rivers including the Congo , Niger , Nile , Orange , Limpopo and Zambezi . In
Pali-Aike volcanic field - Misplaced Pages Continue
2560-573: The Cenozoic ( lit. ' new life ' ) is comparable to the preceding Mesozoic ('middle life') and Paleozoic ('old life') Eras, as well as to the Proterozoic ('earlier life') Eon. The Cenozoic is divided into three periods: the Paleogene , Neogene , and Quaternary ; and seven epochs : the Paleocene , Eocene , Oligocene , Miocene , Pliocene , Pleistocene , and Holocene . The Quaternary Period
2640-539: The Cenozoic is the era when the continents moved into their current positions. Australia-New Guinea , having split from Pangea during the early Cretaceous , drifted north and, eventually, collided with Southeast Asia ; Antarctica moved into its current position over the South Pole ; the Atlantic Ocean widened and, later in the era (2.8 million years ago), South America became attached to North America with
2720-611: The Chile Ridge collided with the Peru–Chile Trench. This collision originally occurred west of Tierra del Fuego , but has since moved northward towards the Taitao Peninsula . Farther south the interaction between the Scotia and South America plates gave rise to the Deseado and Magallanes-Fagnano faults. The Pali-Aike volcanic field is mainly made up of alkali basalt and basanite , which form
2800-589: The Cretaceous, the climate was hot and humid with lush forests at the poles, there was no permanent ice and sea levels were around 300 metres higher than today. This continued for the first 10 million years of the Paleocene, culminating in the Paleocene–Eocene Thermal Maximum about 55.5 million years ago . Around 50 million years ago Earth entered a period of long term cooling. This
2880-477: The Early-Eocene, species living in dense forest were unable to evolve into larger forms, as in the Paleocene. Among them were early primates, whales and horses along with many other early forms of mammals. At the top of the food chains were huge birds, such as Paracrax . Carbon dioxide levels were approximately 1,400 ppm . The temperature was 30 degrees Celsius with little temperature gradient from pole to pole. In
2960-483: The Earth's surface, but tend to be clustered into specific regions. Young volcanoes are rarely found within cratons , but are characteristic of subduction zones, rift zones , or in ocean basins. Intraplate volcanoes are clustered along hotspot traces. Within regions of volcanic activity, volcanic fields are clusters of volcanoes that share a common magma source. Unlike a large volcano with satellite or subsidiary vents,
3040-593: The Laguna Azul maar formed about 3,400 years before present . Humans have lived in the region for thousands of years, and a number of archaeological sites such as the Fell Cave are located in the field. Presently, parts of the volcanic field are protected areas in Chile and Argentina, and the city of Rio Gallegos in Argentina is within 23 kilometres (14 mi) of the volcanic field. The name Pali-Aike comes from
3120-535: The Mid-Eocene, the Antarctic Circumpolar Current between Australia and Antarctica formed. This disrupted ocean currents worldwide and as a result caused a global cooling effect, shrinking the jungles. This allowed mammals to grow to mammoth proportions, such as whales which, by that time, had become almost fully aquatic. Mammals like Andrewsarchus were at the top of the food-chain. The Late Eocene saw
3200-401: The Pali-Aike region since about 10,000 years ago, including various caves such as Fell Cave , Pali-Aike cave, Condor 1, Cueva del Puma, Las Buitreras, Orejas de Burro but also non-cave sites such as Laguna Thomas Gould. Human use of Fell Cave goes back at least 8,000 years and their presence at Pali-Aike is among the oldest human activities in Patagonia. Archaeological research in
3280-428: The area. The origin of oceanic-type magmas close to plate boundaries, which occur in other places of the world as well, is usually attributed to slab-dependent processes. The most important among these is the formation of slab windows (gaps in the downgoing plate which allow asthenosphere to ascend) when spreading ridges collide with subduction zones. The slab window generated by the Chile Ridge's subduction passed at
Pali-Aike volcanic field - Misplaced Pages Continue
3360-454: The changes in the heat flux at the core mantle boundary, climate and plate tectonic activity, shows that all these changes indicate similar rhythms on million years' timescale in the Cenozoic Era occurring with the common fundamental periodicity of ~13 Myr during most of the time. The levels of carbonate ions in the ocean fell over the course of the Cenozoic. Early in the Cenozoic, following
3440-426: The characteristic topography of the volcanic field. The periglacial ground is rich in ice and water, which might explain why there are so many maars in Pali-Aike. Notable among these lakes is Laguna Azul, a crater lake which is located within a pyroclastic ring at the side of a scoria cone. This maar formed during three stages in three separate craters and is also the source of a lava flow. Potrok Aike in comparison
3520-461: The climate. It is divided into two epochs: the Pleistocene and the Holocene. The Pleistocene lasted from 2.58 million to 11,700 years ago. This epoch was marked by ice ages as a result of the cooling trend that started in the Mid-Eocene. There were at least four separate glaciation periods marked by the advance of ice caps as far south as 40° N in mountainous areas. Meanwhile, Africa experienced
3600-466: The course of this era as the world cooled. During the Cenozoic, mammals proliferated from a few small, simple, generalised forms into a diverse collection of terrestrial , marine , and flying animals, giving this period its other name, the Age of Mammals. The Cenozoic is just as much the age of savannas , the age of co-dependent flowering plants and insects , and the age of birds. Grasses also played
3680-541: The crust and control not only the position of the vents, but also the shape of the volcanoes forming on top of the vents. These lines match the strike of the Magallanes-Fagnano fault zone and the older Patagonian Austral Rift. Faults within the field have been active in the Tertiary and into the Holocene , and a graben in the southwestern part of the field has diverted lava flows. The Gallegos River passes north of
3760-494: The dates of these lava flows, it was established that the older and larger glaciation (Bella Vista Glaciation) occurred between 1.17 and 1.02 million years ago. The last glaciation (Cabo Vírgenes, Río Ciaike and Telken VI-I) was less extensive but reached the Atlantic Ocean at times. This glaciation ended before 760,000 years ago; there is no evidence of last glacial maximum / Llanquihue glaciation glaciers in
3840-670: The field to Tierra del Fuego; there is no evidence that a Precambrian basement exists in the Pali-Aike area. During the Oligocene a marine transgression deposited the Patagonia Formation , and during the Miocene fluvial sediments formed the Santa Cruz Formation. Sedimentation ceased in the region 14 million years ago, probably because by that time the rain shadow of the Andes
3920-428: The field. Monogenetic volcanoes are emplaced on the lava plateau at elevations of 110–180 metres (360–590 ft) above sea level and include maars , tuff rings and scoria cones . These various centres rise between 20–160 metres (66–525 ft) above the surrounding terrain. Nested craters, breached craters and fissure vents are common among the various vents, as are lava flows, but there has been little research on
4000-518: The first elephants, cats, dogs, marsupials and many other species still prevalent today. Many other species of plants evolved in this period too. A cooling period featuring seasonal rains was still in effect. Mammals still continued to grow larger and larger. The Neogene spans from 23.03 million to 2.58 million years ago. It features 2 epochs: the Miocene, and the Pliocene. The Miocene Epoch spans from 23.03 to 5.333 million years ago and
4080-416: The form of sediment core analysis, such as Laguna Azul, Potrok Aike and Magallanes Maar. The regional vegetation is grassland and shrubs , with lichens growing on rocks. The dominant grass species is Festuca gracillima , although Festuca pallescens has been described as the dominant species in the wetter west. Festuca is accompanied by bushes of Chiliotrichum diffusum and red crowberry in
SECTION 50
#17328439966984160-561: The form of the Austral Volcanic Zone , a chain of stratovolcanoes and one volcanic field ( Fueguino ), which is South America's southernmost volcano. The Camusu Aike volcanic field, dated at 2.5–2.9 million years old, is 200 kilometres (120 mi) northwest and the Morro Chico volcano about 50 kilometres (31 mi) west of Pali-Aike. At the southern end of South America, the Antarctic Plate subducts beneath South America at
4240-418: The lakes Laguna Salsa and Laguna del Ruido respectively, Bismarck, Carlota, Los Flamencos and Laguna Salida/Laguna Ana. Apart from maars, there are ephemeral lakes . A number of vents form various alignments, usually along northwest–southeast and east–northeast–west–southwest lines; some older centres show a north–south pattern. Such alignments occur when local lineations act as a pathway for magma to ascend to
4320-539: The latitudes of Pali-Aike about 4.5 million years ago; volcanic activity commenced soon afterwards but the time difference was enough for any subduction-influenced mantle to be displaced by fresher mantle moving through the window, which is the main source of the Pali-Aike volcanic rocks. Eight to six million years ago, a change in the motion of the South America Plate relative to the Scotia Plate caused
4400-401: The more recent vents). Maars are depressions in the ground which are encircled by a ring of sediment that rises above the surrounding terrain; they typically form where frozen or liquid water interacts with rising magma and causes explosions. In Pali-Aike there are about 100 of them, with diameters ranging from 500 metres (1,600 ft) to about 4,000 metres (13,000 ft), and they make up
4480-578: The non-avian dinosaurs , became extinct in an event attributed by most experts to the impact of a large asteroid or other celestial body, the Chicxulub impactor . The Cenozoic is also known as the Age of Mammals because the terrestrial animals that dominated both hemispheres were mammals – the eutherians (placentals) in the northern hemisphere and the metatherians (marsupials, now mainly restricted to Australia and to some extent South America ) in
4560-415: The northwestern end of the volcanic field and is heavily eroded. There is no evidence of a systematic migration of vent sites. Potassium–argon dating has yielded ages of between 3.78 and 0.17 million years ago. Several eruptions 770,000 years ago formed maars, including Laguna Timone. The age of Potrok Aike is not known with certainty but its minimum age on the basis of sediment core data
4640-578: The onset of a stretching tectonic regime in the Pali-Aike area, thus allowing the ascent of magmas. The large amounts of xenoliths and primitiveness of the magmas suggest that once they had formed, they very quickly rose through the crust to the surface. Volcanic activity at Pali-Aike spans the late Pliocene to Holocene and has been subdivided into the three units U1, U2 and U3. The oldest U1 unit consists of basaltic plateaus, while U2 and U3 are individual vents with accompanying lava flows. An additional Miocene volcanic stage ("Basaltos Bella Vista") crops out at
4720-655: The origin of long dune fields. Active growth of such windstreaks has been observed in Pali-Aike. Windstreaks are an uncommon occurrence on Earth; they are much more common on Mars . Pali-Aike is part of the Patagonian back-arc , a province of plateau lavas of Cenozoic age. These plateau lavas are of alkaline to tholeiitic composition; hawaiite , trachyandesite and trachyte are present in smaller amounts. From south to north these plateau lavas include Pali-Aike itself, Meseta Vizcachas, Meseta de la Muerte, Gran Meseta Central, Meseta Buenos Aires, Cerro Pedrero, Meseta de Somuncura, Pino Hachado and Buta Ranquil; Pali-Aike
4800-449: The rebirth of seasons, which caused the expansion of savanna-like areas, along with the evolution of grasses . The end of the Eocene was marked by the Eocene–Oligocene extinction event , the European face of which is known as the Grande Coupure . The Oligocene Epoch spans from 33.9 million to 23.03 million years ago. The Oligocene featured the expansion of grasslands which had led to many new species to evolve, including
4880-452: The region is windy and cold, with mild winters owing to the oceanic influence, and dry, bordering on semi-desert with precipitation ranging between 300–150 millimetres per year (11.8–5.9 in/year). These patterns are owing to the closeness of Antarctica , the cold Humboldt current and Falklands current ocean currents and the rain shadow of the Andes. Some maars and craters in Pali-Aike have been used for palaeoclimatological research, in
SECTION 60
#17328439966984960-432: The relatively young, well-preserved rocks associated with it. The Paleogene spans from the extinction of non-avian dinosaurs, 66 million years ago, to the dawn of the Neogene, 23.03 million years ago. It features three epochs : the Paleocene , Eocene and Oligocene . The Paleocene Epoch lasted from 66 million to 56 million years ago. Modern placental mammals originated during this time. The devastation of
5040-504: The rhinoceros-like brontotheres , various bizarre groups of mammals from South America, such as the vaguely elephant-like pyrotheres and the dog-like marsupial relatives called borhyaenids and the monotremes and marsupials of Australia. Mammal evolution in the Cenozoic was predominantly shaped by climatic and geological processes. Cenozoic calcareous nannoplankton experienced rapid rates of speciation and reduced species longevity, while suffering prolonged declines in diversity during
5120-419: The scoria cones. Lava flows embedded in valleys reach lengths of 8 kilometres (5 mi). Pyroclastic cones in Pali-Aike include Aymond, Colorado, Dinero, Fell and Negro. The vent Cerro del Diablo, a pyroclastic cone, is the youngest volcano in the field and has emitted both ʻaʻā and pahoehoe lava , which have a fresh appearance and no soil cover. The vents were origins of lava flows, which sometimes breached
5200-405: The southern hemisphere. The extinction of many groups allowed mammals and birds to greatly diversify so that large mammals and birds dominated life on Earth. The continents also moved into their current positions during this era. The climate during the early Cenozoic was warmer than today, particularly during the Paleocene–Eocene Thermal Maximum . However, the Eocene to Oligocene transition and
5280-442: The strait of Panama, as the isthmus had not yet formed. This epoch featured a general warming trend, with jungles eventually reaching the poles. The oceans were dominated by sharks as the large reptiles that had once predominated were extinct. Archaic mammals filled the world such as creodonts (extinct carnivores, unrelated to existing Carnivora ). The Eocene Epoch ranged from 56 million years to 33.9 million years ago. In
5360-499: The vents. Some flows are older and covered with soil while younger ones are not. Such young lava flows also have surface features including lava tunnels , hornitos , tumuli and a wrinkled surface. Some of these are heavily eroded while the southeastern part of the field features fresh-looking centres, where they form the "Basaltos del Diablo". The individual volcanoes are subdivided into three groups, which are referred to as "U1" (the plateau lavas), "U2" (the older centres) and "U3" (for
5440-400: The volcanic field and Argentine National Route 3 passes through the Pali-Aike volcanic field. The border crossing Paso Integración Austral lies next to the volcanic field. On the Chilean side there are hiking trails. The Pali-Aike volcanic field covers a surface area of 4,500 square kilometres (1,700 square miles), and extends over 150 kilometres (93 mi) from northwest to southeast. It
5520-526: The volcanic field began in the 1930s. Prehistoric human activity was concentrated in the southern, wetter sector of the volcanic field. The lakes, rivers and the volcanic landscape have a reliable supply of water and offered refuge to these people, drawing them to the volcanic field; in turn they might have settled the rest of the wider region starting from Pali-Aike. They left archaeological sites , petroglyphs , rock carvings and stone tools behind; even some ancient burials have been found. The volcanic field
5600-541: The volcanic field, while its tributary Rio Chico crosses the volcanic field from southwest to northeast. The terrain of the field is highly permeable to water, which later forms wetlands that attract a number of birds and springs that are used as a source of water. Maars are not the only water bodies within the field; lakes formed by lava dams , glacial lakes and lakes formed by wind deflation also exist. Some of these water bodies dry up late in summer, allowing wind to remove sediments from their lakebeds, which thus become
5680-481: The west–central part of the field may be the formerly underground components of now-eroded volcanic edifices. Among these volcanic necks are the Cuadrado, Domeyko, Gay and Philippi hills, which conspicuously stick out of the surrounding plains. The volcanic rocks were emplaced atop Cenozoic - to Tertiary -age sediments , which were smoothened by glacial action. The sediments are often unstable and prone to mass wasting and landslides . There are 467 volcanic vents in
5760-884: The wetter regions and by bushes of Nardophyllum bryoides and Nassauvia ulicina in the drier regions. Various herbs and dicots complete the regional flora. The highly permeable basalts intercept precipitation, forming active aquifers that feed into wetlands. Animal species present in the Chilean national park include armadillos , gray foxes , guanacos , Humboldt's hog-nosed skunks , pumas and red foxes . Bird species include Chloephaga and Theristicus species, black-chested buzzard-eagles , cinereous harriers , crested caracaras , harriers , kestrels , peregrine falcons , rheas and southern lapwings , but also aquatic birds like Calidris species, Coscoroba swans , flamingos , two-banded plovers , yellow-billed pintails and yellow-billed teals . Palaeorecords indicate that ecological conditions varied from place to place in
5840-416: The wider region and during the last 50,000 years. Caves have yielded fossils of animals that lived there during the Holocene and Pleistocene such as big cats and ground sloths , although the former fauna in the region is poorly studied. Since the arrival of Europeans in the late 19th century, invasive European weeds and sheep farming have altered the regional ecosystem. Early humans inhabited
5920-581: The world was dominated by the gastornithid birds, terrestrial crocodylians like Pristichampsus , large sharks such as Otodus , and a handful of primitive large mammal groups like uintatheres , mesonychians , and pantodonts . But as the forests began to recede and the climate began to cool, other mammals took over. The Cenozoic is full of mammals both strange and familiar, including chalicotheres , creodonts , whales , primates , entelodonts , sabre-toothed cats , mastodons and mammoths , three-toed horses , giant rhinoceros like Paraceratherium ,
6000-505: The world's megafauna, including some of the hominid species, such as Neanderthals . All the continents were affected, but Africa to a lesser extent. It still retains many large animals, such as hippos. The Holocene began 11,700 years ago and lasts to the present day. All recorded history and "the Human history " lies within the boundaries of the Holocene Epoch. Human activity is blamed for
6080-684: The world; Indian monsoons ; deserts in central Asia ; and the beginnings of the Sahara desert. The world map has not changed much since, save for changes brought about by the glaciations of the Quaternary, such as the Great Lakes , Hudson Bay , and the Baltic Sea . The Quaternary spans from 2.58 million years ago to present day, and is the shortest geological period in the Phanerozoic Eon . It features modern animals, and dramatic changes in
6160-490: Was a source of volcanic rocks such as obsidian for the manufacturing of archaeological artifacts but, perhaps because of the low quality of the rocks, they had only limited use. Weathered volcanic rocks from the Pali-Aike volcanic field were used as red pigments in rock art. Today sheep are farmed in the volcanic field. On the Chilean side, the Pali-Aike volcanic field is part of the Pali-Aike National Park and
6240-469: Was effective in the area. At that time, the Chile Ridge first collided with the Peru–Chile Trench west of Tierra del Fuego; since then the collision zone has migrated north to the Taitao Peninsula off western Chile. Moraines occur west and south from the volcanic field. The Pali-Aike area was glaciated during the middle Pleistocene , and glaciers eroded contemporary lava flows. In part on the basis of
6320-530: Was mainly due to the collision of India with Eurasia, which caused the rise of the Himalayas : the upraised rocks eroded and reacted with CO 2 in the air, causing a long-term reduction in the proportion of this greenhouse gas in the atmosphere. Around 35 million years ago permanent ice began to build up on Antarctica. The cooling trend continued in the Miocene , with relatively short warmer periods. When South America became attached to North America creating
6400-662: Was officially recognised by the International Commission on Stratigraphy in June 2009. In 2004, the Tertiary Period was officially replaced by the Paleogene and Neogene Periods. The common use of epochs during the Cenozoic helps palaeontologists better organise and group the many significant events that occurred during this comparatively short interval of time. Knowledge of this era is more detailed than any other era because of
#697302