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73-796: The Central Cordillera, some peaks of which are capped with ice , consists of (from east to west): the Central Highlands and Eastern Highlands of Papua New Guinea including the Owen Stanley Range in the southeast, whose highest peak is Mount Victoria at 4,038 metres (13,248 feet), the Albert Victor Mountains, the Sir Arthur Gordon Range, and the Bismarck Range , whose highest peak is Mount Wilhelm at 4,509 metres (14,793 feet), which

146-521: A cuscus possum, an antechinus , and Doria's tree-kangaroo ( Dendrolagus dorianus ). Four of these are endemic: the small marsupial black-tailed antechinus ( Murexechinus melanurus ), western shrew mouse , glacier rat , and alpine woolly rat . There are nearly 100 birds of which 28 are considered endemic or nearly so, including the vulnerable long-bearded honeyeater ( Melionyx princeps ), ribbon-tailed astrapia ( Astrapia mayeri ), and Macgregor's giant honeyeater , which although endangered generally

219-661: A type section , Global Boundary Stratotype Section and Point (GSSP), for the upper Pleistocene/Holocene boundary ( i.e. the upper boundary). The proposed section is the North Greenland Ice Core Project ice core 75° 06' N 42° 18' W. The lower boundary of the Pleistocene Series is formally defined magnetostratigraphically as the base of the Matuyama (C2r) chronozone , isotopic stage 103. Above this point there are notable extinctions of

292-504: A 95 ± 29  mm rise in global sea levels until they reach equilibrium. However, environmental conditions have worsened and are predicted to continue to worsen in the future. Given that the rate of melting will accelerate, and by using mathematical models to predict future climate patterns, the actual contribution of ice caps to rising sea levels is expected to be more than double from initial estimates. High-latitude regions covered in ice, though strictly not an ice cap (since they exceed

365-611: A change from low-amplitude glacial cycles with a dominant periodicity of 41,000 years to asymmetric high-amplitude cycles dominated by a periodicity of 100,000 years. However, a 2020 study concluded that ice age terminations might have been influenced by obliquity since the Mid-Pleistocene Transition, which caused stronger summers in the Northern Hemisphere . Glaciation in the Pleistocene

438-574: A deviation from today's annual mean temperature, taken as zero. This sort of graph is based on another isotope ratio versus time. Ratios are converted to a percentage difference from the ratio found in standard mean ocean water (SMOW). The graph in either form appears as a waveform with overtones . One half of a period is a Marine isotopic stage (MIS). It indicates a glacial (below zero) or an interglacial (above zero). Overtones are stadials or interstadials. According to this evidence, Earth experienced 102 MIS stages beginning at about 2.588 Ma BP in

511-421: A few regions had been studied and the names were relatively few. Today the geologists of different nations are taking more of an interest in Pleistocene glaciology. As a consequence, the number of names is expanding rapidly and will continue to expand. Many of the advances and stadials remain unnamed. Also, the terrestrial evidence for some of them has been erased or obscured by larger ones, but evidence remains from

584-557: A large Leptomys , the eastern shrew mouse , and the lesser small-toothed rat . There are 55 bird species endemic to the mountains from a total of 348 birds found here. There are several endemic butterflies, particularly in the Weyland Mountains and the Wahgi Valley. Apart from the cultivated valleys, the montane forests are largely intact, although the logging industry is a constant threat as more and more access to

657-578: A team of Russian scientists in collaboration with Princeton University announced that they had brought two female nematodes frozen in permafrost , from around 42,000 years ago, back to life. The two nematodes, at the time, were the oldest confirmed living animals on the planet. The evolution of anatomically modern humans took place during the Pleistocene. At the beginning of the Pleistocene Paranthropus species were still present, as well as early human ancestors, but during

730-601: Is Biscayarfonna in Svalbard . Hypothetical runaway greenhouse state Tropical temperatures may reach poles Global climate during an ice age Earth's surface entirely or nearly frozen over Pleistocene The Pleistocene ( / ˈ p l aɪ s t ə ˌ s iː n , - s t oʊ -/ PLY -stə-seen, -⁠stoh- ; referred to colloquially as the Ice Age ) is the geological epoch that lasted from c.  2.58 million to 11,700 years ago, spanning

803-560: Is a cultural icon of the Ketengban people of the Star Mountains and therefore protected in some areas. Almost half of these remote grasslands are protected in national parks and they are in good condition although in recent times more people are accessing the highlands as visitors or through involvement in mining. There are several protected areas in the highlands. They include: Ice cap In glaciology , an ice cap

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876-487: Is a mass of ice that covers less than 50,000 km (19,000 sq mi) of land area (usually covering a highland area). Larger ice masses covering more than 50,000 km (19,000 sq mi) are termed ice sheets . Ice caps are not constrained by topographical features (i.e., they will lie over the top of mountains). By contrast, ice masses of similar size that are constrained by topographical features are known as ice fields . The dome of an ice cap

949-756: Is an extinct volcano with a crater lake; the Star Mountains on the Papua New Guinea – Indonesia border; and the Maoke Mountains or Snow Range in Indonesia, where perpetual snow was found by H. A. Lorentz in 1909 at 4,461 m (14,635 ft), and whose highest peaks are Puncak Jaya (Mt. Carstensz) at 4,884 m (16,024 feet), Puncak Mandala (Mt. Juliana) at 4,760 m (15,610 ft) and Puncak Trikora (Mt. Wilhelmina) at 4,750 m (15,580 ft). Although some valleys such as

1022-669: Is determined by the landscape it lies on, as melting patterns can vary with terrain. For example, the lower portions of an ice cap are forced to flow outwards under the weight of the entire ice cap and will follow the downward slopes of the land. Ice caps have been used as indicators of global warming, as increasing temperatures cause ice caps to melt and lose mass faster than they accumulate mass. Ice cap size can be monitored through different remote-sensing methods such as aircraft and satellite data. Ice caps accumulate snow on their upper surfaces, and ablate snow on their lower surfaces. An ice cap in equilibrium accumulates and ablates snow at

1095-781: Is estimated that, at maximum glacial extent, 30% of the Earth's surface was covered by ice. In addition, a zone of permafrost stretched southward from the edge of the glacial sheet, a few hundred kilometres in North America , and several hundred in Eurasia . The mean annual temperature at the edge of the ice was −6 °C (21 °F); at the edge of the permafrost, 0 °C (32 °F). Each glacial advance tied up huge volumes of water in continental ice sheets 1,500 to 3,000 metres (4,900–9,800 ft) thick, resulting in temporary sea-level drops of 100 metres (300 ft) or more over

1168-459: Is no systematic correspondence between pluvials to glacials, however. Moreover, regional pluvials do not correspond to each other globally. For example, some have used the term "Riss pluvial" in Egyptian contexts. Any coincidence is an accident of regional factors. Only a few of the names for pluvials in restricted regions have been stratigraphically defined. The sum of transient factors acting at

1241-654: Is usually centred on the highest point of a massif . Ice flows away from this high point (the ice divide ) towards the ice cap's periphery. Ice caps significantly affect the geomorphology of the area they occupy. Plastic moulding, gouging and other glacial erosional features become present upon the glacier's retreat. Many lakes, such as the Great Lakes in North America, as well as numerous valleys have been formed by glacial action over hundreds of thousands of years. The Antarctic and Greenland contain 99% of

1314-659: The Alpine ice sheet on the Alps . Scattered domes stretched across Siberia and the Arctic shelf. The northern seas were ice-covered. South of the ice sheets large lakes accumulated because outlets were blocked and the cooler air slowed evaporation. When the Laurentide Ice Sheet retreated, north-central North America was completely covered by Lake Agassiz . Over a hundred basins, now dry or nearly so, were overflowing in

1387-571: The Australian Plate collides with the plates to the northeast, marking the southern boundaries of the Maoke and Woodlark plates. The width of the mountain range varies considerably, with a central thin segment near the borders of the two nations. The surface geology of the highlands is made up of metamorphic and intrusive igneous rocks. The metamorphic rocks were Cretaceous and Eocene ocean sediments that were uplifted and folded between

1460-662: The Ruwenzori Range in east and central Africa were larger. Glaciers existed in the mountains of Ethiopia and to the west in the Atlas Mountains . In the northern hemisphere, many glaciers fused into one. The Cordilleran Ice Sheet covered the North American northwest; the east was covered by the Laurentide . The Fenno-Scandian ice sheet rested on northern Europe , including much of Great Britain;

1533-609: The Waghi Valley in the Western Highlands , Papua New Guinea are heavily cultivated and support urban settlements most of the mountains have traditional tribal village communities in the grassy mountain valleys. The PNG highland provinces are Eastern Highlands Province ; Simbu Province (or Chimbu) whose centre is the small coffee-growing town of Kundiawa on the Wahgi River near Mount Wilhelm; Jiwaka Province ;

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1606-666: The Western Highlands ; the rugged Enga Province the home of the Enga people with its administration in the very small town of Wabag on the Lai River , and containing the large Porgera Gold Mine ; Hela Province ; Southern Highlands Province , with its centre in the small town and airport of Mendi , and containing the Huli wigmen area around the town of Tari ; and parts of West Sepik Province and Western Province . The Highlands Highway connects many of these towns. Larger urban areas in

1679-437: The calcareous nannofossils : Discoaster pentaradiatus and Discoaster surculus . The Pleistocene covers the recent period of repeated glaciations. The name Plio-Pleistocene has, in the past, been used to mean the last ice age. Formerly, the boundary between the two epochs was drawn at the time when the foraminiferal species Hyalinea baltica first appeared in the marine section at La Castella, Calabria, Italy. However,

1752-477: The last glacial period ended about 10,000 years ago. Over 11 major glacial events have been identified, as well as many minor glacial events. A major glacial event is a general glacial excursion, termed a "glacial." Glacials are separated by "interglacials". During a glacial, the glacier experiences minor advances and retreats. The minor excursion is a "stadial"; times between stadials are "interstadials". These events are defined differently in different regions of

1825-599: The woolly rhinoceros , various giraffids , such as the Sivatherium ; ground sloths , Irish elk , cave lions , cave bears , Gomphotheres , American lions , dire wolves , and short-faced bears , began late in the Pleistocene and continued into the Holocene. Neanderthals also became extinct during this period. At the end of the last ice age, cold-blooded animals, smaller mammals like wood mice , migratory birds, and swifter animals like whitetail deer had replaced

1898-724: The "Tarantian"). In addition to these international subdivisions, various regional subdivisions are often used. In 2009 the International Union of Geological Sciences (IUGS) confirmed a change in time period for the Pleistocene, changing the start date from 1.806 to 2.588 million years BP, and accepted the base of the Gelasian as the base of the Pleistocene, namely the base of the Monte San Nicola GSSP . The start date has now been rounded down to 2.580 million years BP. The IUGS has yet to approve

1971-531: The 90 mammals found on the island, 44 are endemic, a very high proportion. The birds and animals include many Australasian species such as tree-kangaroos , bowerbirds , Australasian robins , honeyeaters , and birds of paradise. Four of the endemic mammals are critically endangered: the Bulmer's fruit bat , with only tiny communities remaining in the Papua New Guinea end of the island, and three rodents;

2044-515: The Australian mainland. The culture of inter-tribal warfare and animosity between the neighboring tribes have long been present in the Highlands. The New Guinea Highlands are home to a great variety of Australasian plant and animal communities, distinct from the surrounding lowlands to the north and south of the central ranges and varying up and along the mountain ranges. The habitats of

2117-569: The Early Pleistocene Gelasian . Early Pleistocene stages were shallow and frequent. The latest were the most intense and most widely spaced. By convention, stages are numbered from the Holocene, which is MIS1. Glacials receive an even number and interglacials receive an odd number. The first major glacial was MIS2-4 at about 85–11 ka BP. The largest glacials were 2, 6, 12, and 16. The warmest interglacials were 1, 5, 9 and 11. For matching of MIS numbers to named stages, see under

2190-402: The Earth's most recent period of repeated glaciations . Before a change was finally confirmed in 2009 by the International Union of Geological Sciences , the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with

2263-409: The Earth's surface is cyclical: climate, ocean currents and other movements, wind currents, temperature, etc. The waveform response comes from the underlying cyclical motions of the planet, which eventually drag all the transients into harmony with them. The repeated glaciations of the Pleistocene were caused by the same factors. The Mid-Pleistocene Transition , approximately one million years ago, saw

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2336-555: The Eocene and early Miocene periods. There are also Pleistocene stratovolcanoes in the highlands, including Mount Hagen and Mount Giluwe . The fertile Highlands have long been inhabited and artifacts uncovered in the Ivane Valley indicate that the Highlands were first settled about 50,000 years ago. The inhabitants were nomadic foragers but around 10,000 years ago began developing a fairly advanced agricultural society. Before

2409-877: The Indonesian border including Telefomin and Strickland Gorge ; the Hunstein Range ; Mount Giluwe , a major birdwatching area for birds-of-paradise ; the volcanic limestone Kubor Range ; the Bismarck Range/Mount Wilhelm/ Schrader Range /Mount Gahavisuka , of which Mount Wilhelm is particularly rich in endemic species; and finally the Crater Mountain and Mount Michael in the Eastern Highlands. The montane rain forests (from 1,000 to 3,000m) can be further categorised into three broad vegetation zones on

2482-479: The North American west. Lake Bonneville , for example, stood where Great Salt Lake now does. In Eurasia, large lakes developed as a result of the runoff from the glaciers. Rivers were larger, had a more copious flow, and were braided . African lakes were fuller, apparently from decreased evaporation. Deserts, on the other hand, were drier and more extensive. Rainfall was lower because of the decreases in oceanic and other evaporation. It has been estimated that during

2555-556: The PNG Highlands include the Western Highlands capital and PNG's 3rd largest city Mount Hagen (near the extinct Mount Hagen (volcano) ), the Eastern Highlands capital and former colonial town of Goroka , and the mining town of Tabubil . The climate is humid as you would expect of the tropical rainforested island of New Guinea, but the higher mountain slopes are of course cooler than the lowlands. The Highlands are

2628-496: The Pleistocene's overall climate could be characterised as a continuous El Niño with trade winds in the south Pacific weakening or heading east, warm air rising near Peru , warm water spreading from the west Pacific and the Indian Ocean to the east Pacific, and other El Niño markers. Pleistocene climate was marked by repeated glacial cycles in which continental glaciers pushed to the 40th parallel in some places. It

2701-805: The Pleistocene, the East Antarctic Ice Sheet thinned by at least 500 meters, and that thinning since the Last Glacial Maximum is less than 50 meters and probably started after ca 14 ka. During the 2.5 million years of the Pleistocene, numerous cold phases called glacials ( Quaternary ice age ), or significant advances of continental ice sheets, in Europe and North America, occurred at intervals of approximately 40,000 to 100,000 years. The long glacial periods were separated by more temperate and shorter interglacials which lasted about 10,000–15,000 years. The last cold episode of

2774-411: The Pleistocene, the plates upon which they sit probably having moved no more than 100 km (62 mi) relative to each other since the beginning of the period. In glacial periods, the sea level would drop by up to 120 m (390 ft) lower than today during peak glaciation, exposing large areas of the present continental shelf as dry land. According to Mark Lynas (through collected data),

2847-633: The Pleistocene. The climate was strongly variable depending on the glacial cycle, with the sea levels being up to 120 metres (390 ft) lower than present at peak glaciation, allowing the connection of Asia and North America via Beringia and the covering of most of northern North America by the Laurentide Ice Sheet . Charles Lyell introduced the term "Pleistocene" in 1839 to describe strata in Sicily that had at least 70% of their molluscan fauna still living today. This distinguished it from

2920-600: The Wahgi Valley and Mount Hagen , and Richard Archbold in the 1930s. It was found that the highland valleys explored in the 1930s were inhabited by over a million people. During World War II , the eastern highlands saw the Kokoda Track campaign in which Australian and New Zealand soldiers, along with native guides who were pressed into service, fought and ultimately stopped the Japanese from advancing south towards Port Moresby and, ultimately, northern Queensland on

2993-535: The Younger Dryas is the official start of the current Holocene Epoch . Although it is considered an epoch, the Holocene is not significantly different from previous interglacial intervals within the Pleistocene. In the ICS timescale, the Pleistocene is divided into four stages or ages , the Gelasian , Calabrian , Chibanian (previously the unofficial "Middle Pleistocene"), and Upper Pleistocene (unofficially

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3066-706: The appearance of Homo sapiens about 300,000 years ago. Artifacts associated with modern human behavior are unambiguously attested starting 40,000–50,000 years ago. According to mitochondrial timing techniques, modern humans migrated from Africa after the Riss glaciation in the Middle Palaeolithic during the Eemian Stage , spreading all over the ice-free world during the late Pleistocene. A 2005 study posits that humans in this migration interbred with archaic human forms already outside of Africa by

3139-527: The articles for those names. Both marine and continental faunas were essentially modern but with many more large land mammals such as Mammoths , Mastodons , Diprotodons , Smilodons , tigers , lions , Aurochs , short-faced bears , giant sloths , species within Gigantopithecus and others. Isolated landmasses such as Australia , Madagascar , New Zealand and islands in the Pacific saw

3212-479: The climate variation more extreme. The Late Pleistocene witnessed the spread of modern humans outside of Africa as well as the extinction of all other human species. Humans also spread to the Australian continent and the Americas for the first time, co-incident with the extinction of most large-bodied animals in these regions. The aridification and cooling trends of the preceding Neogene were continued in

3285-540: The end of the last glacial period and also with the end of the Paleolithic age used in archaeology . The name is a combination of Ancient Greek πλεῖστος ( pleîstos ) 'most' and καινός ( kainós ; Latinized as cænus ) 'new'. At the end of the preceding Pliocene, the previously isolated North and South American continents were joined by the Isthmus of Panama , causing a faunal interchange between

3358-618: The entire surface of the Earth. During interglacial times, such as at present, drowned coastlines were common, mitigated by isostatic or other emergent motion of some regions. The effects of glaciation were global. Antarctica was ice-bound throughout the Pleistocene as well as the preceding Pliocene. The Andes were covered in the south by the Patagonian ice cap. There were glaciers in New Zealand and Tasmania . The current decaying glaciers of Mount Kenya , Mount Kilimanjaro , and

3431-782: The evolution of large birds and even reptiles such as the Elephant bird , moa , Haast's eagle , Quinkana , Megalania and Meiolania . The severe climatic changes during the Ice Age had major impacts on the fauna and flora. With each advance of the ice, large areas of the continents became depopulated, and plants and animals retreating southwards in front of the advancing glacier faced tremendous stress. The most severe stress resulted from drastic climatic changes, reduced living space, and curtailed food supply. A major extinction event of large mammals ( megafauna ), which included mammoths , mastodons , saber-toothed cats , glyptodons ,

3504-414: The glacial range, which have their own glacial history depending on latitude, terrain and climate. There is a general correspondence between glacials in different regions. Investigators often interchange the names if the glacial geology of a region is in the process of being defined. However, it is generally incorrect to apply the name of a glacial in one region to another. For most of the 20th century, only

3577-449: The high mountain forest extends from 2,500 to 3,000 metres in elevation. Conifers ( Podocarpus , Dacrycarpus , Dacrydium , Papuacedrus , Araucaria , and Libocedrus ) and broadleaf trees of the myrtle family ( Myrtaceae ) form a thin canopy, with a prominent understory. The montane forests are home to a rich wildlife, a great deal of which is unique to these mountains including many plants, reptiles, and over 100 birds and animals. Of

3650-450: The historical terminology was established. Corresponding to the terms glacial and interglacial, the terms pluvial and interpluvial are in use (Latin: pluvia , rain). A pluvial is a warmer period of increased rainfall; an interpluvial is of decreased rainfall. Formerly a pluvial was thought to correspond to a glacial in regions not iced, and in some cases it does. Rainfall is cyclical also. Pluvials and interpluvials are widespread. There

3723-440: The ice volume on earth, about 33 million cubic kilometres (7.9 million cubic miles) of total ice mass. Ice caps are formed when snow is deposited during the cold season and fails to completely melt during the hot season. Over time, the snow builds up and becomes dense, well-bonded snow known as perennial firn . Finally, the air passages between snow particles close off and transforms into ice. The shape of an ice cap

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3796-552: The introduction of the sweet potato , the Highlands had distinct forms of division of labor . In the Eastern Highlands the economy was mixed, with men hunting and cultivating, and women gathering and tending crops. Populations were small, dispersed, and focused on immediate consumption. In the Western Highlands , women were focused on producing large amounts of taro , while men abandoned hunting and were instead focused on animal husbandry and trading. The introduction of

3869-622: The large amounts of material moved about by glaciers. Less common are cave deposits, travertines and volcanic deposits (lavas, ashes). Pleistocene marine deposits are found primarily in shallow marine basins mostly (but with important exceptions) in areas within a few tens of kilometres of the modern shoreline. In a few geologically active areas such as the Southern California coast, Pleistocene marine deposits may be found at elevations of several hundred metres. The modern continents were essentially at their present positions during

3942-461: The long term, the AAR of glaciers has been about 0.57. In contrast, data from the most recent years of 1997–2006 yields an AAR of only 0.44. In other words, glaciers and ice caps are accumulating less snow and are out of equilibrium, causing melting and contributing to sea level rises. Assuming the climate continues to be in the same state as it was in 2006, it is estimated that ice caps will contribute

4015-470: The lower Palaeolithic they disappeared, and the only hominin species found in fossilic records is Homo erectus for much of the Pleistocene. Acheulean lithics appear along with Homo erectus , some 1.8 million years ago, replacing the more primitive Oldowan industry used by A. garhi and by the earliest species of Homo . The Middle Paleolithic saw more varied speciation within Homo , including

4088-461: The maximum area specified in the definition above), are called polar ice caps ; the usage of this designation is widespread in the mass media and arguably recognized by experts. Vatnajökull is an example of an ice cap in Iceland . Plateau glaciers are glaciers that overlie a generally flat highland area. Usually, the ice overflows as hanging glaciers in the lower parts of the edges. An example

4161-478: The megafauna and migrated north. Late Pleistocene bighorn sheep were more slender and had longer legs than their descendants today. Scientists believe that the change in predator fauna after the late Pleistocene extinctions resulted in a change of body shape as the species adapted for increased power rather than speed. The extinctions hardly affected Africa but were especially severe in North America where native horses and camels were wiped out. In July 2018,

4234-450: The mountains have been separated into two ecoregions , depending on their elevation, the tropical montane forests and alpine grasslands, but within these broad bands there is a variety of wildlife along the island as some of the mountains stand quite a distance from others with some species of plant or animal existing on only one or two mountains. Particular centres of plant diversity are the Star Mountains area of western Papua New Guinea near

4307-670: The mountains is achieved by road building. 20% of this ecoregion is contained within protected areas, mostly in the Indonesian half of the island, including the largest protected area in Southeast Asia , the huge Lorentz National Park in the highlands, a section of which is a montane forest ecosystem. Above 3,000 metres elevation, the high mountain forest transitions to remote sub-alpine habitats including alpine meadows, conifer forest, tree-fern ( Cyathea ) grasslands, bogs, and shrubby heaths of Rhododendron , Vaccinium , Coprosma , Rapanea , and Saurauia all quite different from

4380-438: The mountains, distinguished by elevation. The lower montane forests extend from 1,000 to 1,500 metres elevation. They are dominated by broadleaf evergreen trees, including Castanopsis acuminatissima , Lithocarpus spp., elaeocarps , and laurels . Coniferous Araucarias may form thick stands. The upper montane forests, which extend from 1,500 to 2,500 metres in elevation, are dominated by moss-covered Nothofagus . Finally,

4453-581: The older Pliocene Epoch , which Lyell had originally thought to be the youngest fossil rock layer. He constructed the name "Pleistocene" ('most new' or 'newest') from the Greek πλεῖστος ( pleīstos ) 'most' and καινός ( kainós ( Latinized as cænus ) 'new'). This contrasts with the immediately preceding Pliocene ("newer", from πλείων ( pleíōn , "more") and kainós ) and the immediately subsequent Holocene ("wholly new" or "entirely new", from ὅλος ( hólos , "whole") and kainós ) epoch , which extends to

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4526-465: The present time. The Pleistocene has been dated from 2.580 million (±0.005) to 11,700 years BP with the end date expressed in radiocarbon years as 10,000 carbon-14 years BP. It covers most of the latest period of repeated glaciation , up to and including the Younger Dryas cold spell. The end of the Younger Dryas has been dated to about 9700 BCE (11,700 calendar years BP). The end of

4599-417: The ratio of O to O (two isotopes of oxygen ) by mass (measured by a mass spectrometer ) present in the calcite of oceanic core samples is used as a diagnostic of ancient ocean temperature change and therefore of climate change. Cold oceans are richer in O , which is included in the tests of the microorganisms ( foraminifera ) contributing the calcite. A more recent version of

4672-570: The revised definition of the Quaternary , by pushing back the start date of the Pleistocene to 2.58 Ma, results in the inclusion of all the recent repeated glaciations within the Pleistocene. Radiocarbon dating is considered to be inaccurate beyond around 50,000 years ago. Marine isotope stages (MIS) derived from Oxygen isotopes are often used for giving approximate dates. Pleistocene non-marine sediments are found primarily in fluvial deposits , lakebeds, slope and loess deposits as well as in

4745-423: The same rate. The AAR is the ratio between the accumulation area and the total area of the ice cap, which is used to indicate the health of the glacier. Depending on their shape and mass, healthy glaciers in equilibrium typically have an AAR of approximately 0.4 to 0.8. The AAR is impacted by environmental conditions such as temperature and precipitation. Data from 86 mountain glaciers and ice caps shows that over

4818-407: The sampling process makes use of modern glacial ice cores. Although less rich in O than seawater, the snow that fell on the glacier year by year nevertheless contained O and O in a ratio that depended on the mean annual temperature. Temperature and climate change are cyclical when plotted on a graph of temperature versus time. Temperature coordinates are given in the form of

4891-649: The sole factor responsible for the variations in climate since they explain neither the long-term cooling trend over the Plio-Pleistocene nor the millennial variations in the Greenland Ice Cores known as Dansgaard-Oeschger events and Heinrich events. Milankovitch pacing seems to best explain glaciation events with periodicity of 100,000, 40,000, and 20,000 years. Such a pattern seems to fit the information on climate change found in oxygen isotope cores. In oxygen isotope ratio analysis, variations in

4964-705: The source of several important rivers including the Sepik River and Ramu River in the north and the Fly River in the south, and lakes including Lake Kutubu , near which oil has been extracted since 1992 by Chevron . Mining is also very active in the region to the detriment of indigenous groups, with frequent friction. List of highest peaks in New Guinea Highlands by elevation. List of rivers in New Guinea Highlands by length. This chain of mountains continues to rise (with corresponding quakes) as

5037-421: The study of cyclical climate changes. The glacials in the following tables show historical usages, are a simplification of a much more complex cycle of variation in climate and terrain, and are generally no longer used. These names have been abandoned in favour of numeric data because many of the correlations were found to be either inexact or incorrect and more than four major glacials have been recognised since

5110-572: The sweet potato had a significant impact on animal husbandry in the area. As it could be used as pig fodder without the need for cooking, societies that adopted this new staple food were able to rapidly amass pigs. These pigs were then traded with surrounding societies, becoming the centerpiece of early economies in the area. The Highlands were not settled by the Western powers during the early colonial period and they were first visited by western zoologists and explorers, such as Mick Leahy , who opened

5183-431: The tropical rain forest that covers most of New Guinea. The alpine habitat above 4,000 metres consists of compact rosette plants and cushion herbs, such as Ranunculus , Potentilla , Gentiana , and Epilobium , grasses ( Poa and Deschampsia ), bryophytes , and lichens . While there are several endemic plants there are few animals on the higher slopes, with only nine mammals found here: four rodents, two bats,

5256-764: The two regions and changing ocean circulation patterns, with the onset of glaciation in the Northern Hemisphere occurring around 2.7 million years ago. During the Early Pleistocene (2.58–0.8 Ma), archaic humans of the genus Homo originated in Africa and spread throughout Afro-Eurasia . The end of the Early Pleistocene is marked by the Mid-Pleistocene Transition , with the cyclicity of glacial cycles changing from 41,000-year cycles to asymmetric 100,000-year cycles, making

5329-543: Was a series of glacials and interglacials, stadials and interstadials, mirroring periodic climate changes. The main factor at work in climate cycling is now believed to be Milankovitch cycles . These are periodic variations in regional and planetary solar radiation reaching the Earth caused by several repeating changes in the Earth's motion. The effects of Milankovitch cycles were enhanced by various positive feedbacks related to increases in atmospheric carbon dioxide concentrations and Earth's albedo. Milankovitch cycles cannot be

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