Misplaced Pages

#746253

68-725: The term "Goldthwait Sea" was proposed by Elson in 1969 to distinguish the area from the Champlain Sea and the Laflamme Sea. The sea is named after the geologist James Walter Goldthwait (1880–1947). He did impressive work for the Geological Survey of Canada in the east of the country, and in Quebec in particular, despite handicaps such as lack of aerial photographs or detailed topographical maps. The quality of his observations and his insights were remarkable. Formation of

136-400: A much longer phase of retreat as the continent rose isostatically, a process that is not yet fully complete. Dionne (1977) proposes three major episodes: Lower Goldthwaitian 13,500 to 12,000 years ago, Middle Goldthwaitian 12,000 to 9,000 years ago, and Upper Goldthwaitian, 9,000 years ago until the present. Complicating the picture is that deglaciation did not occur at the same time throughout

204-527: A result of melting ice, the land has continued to rise yearly in Scandinavia, mostly in northern Sweden and Finland, where the land is rising at a rate of as much as 8–9 mm per year, or 1 m in 100 years. This is important for archaeologists, since a site that was coastal in the Nordic Stone Age now is inland and can be dated by its relative distance from the present shore. The term Würm

272-797: A still lesser extent, glaciers existed in Africa, for example in the High Atlas , the mountains of Morocco , the Mount Atakor massif in southern Algeria , and several mountains in Ethiopia . Just south of the equator, an ice cap of several hundred square kilometers was present on the east African mountains in the Kilimanjaro massif , Mount Kenya , and the Rwenzori Mountains , which still bear relic glaciers today. Glaciation of

340-793: Is an important river in the Port-Cartier–Sept-Îles Wildlife Reserve . It originates in Lake Bourgeois, one of the lakes along the route of the Cartier Railway , and flows southeast to enter the Gulf of Saint Lawrence just west of the community of Rivière-Pentecôte. The Riverin River flows under Quebec Route 138 and into the Saint Lawrence through the community of Rivière-Pentecôte. Just east of Route 138

408-605: Is derived from a river in the Alpine foreland, roughly marking the maximum glacier advance of this particular glacial period. The Alps were where the first systematic scientific research on ice ages was conducted by Louis Agassiz at the beginning of the 19th century. Here, the Würm glaciation of the LGP was intensively studied. Pollen analysis , the statistical analyses of microfossilized plant pollens found in geological deposits, chronicled

476-1024: The Central Rocky Mountains ), Wisconsinan or Wisconsin (in central North America), Devensian (in the British Isles), Midlandian (in Ireland), Würm (in the Alps ), Mérida (in Venezuela ), Weichselian or Vistulian (in Northern Europe and northern Central Europe), Valdai in Russia and Zyryanka in Siberia , Llanquihue in Chile , and Otira in New Zealand. The geochronological Late Pleistocene includes

544-670: The Himalayas , and other formerly glaciated regions around the world. The glaciations that occurred during this glacial period covered many areas, mainly in the Northern Hemisphere and to a lesser extent in the Southern Hemisphere. They have different names, historically developed and depending on their geographic distributions: Fraser (in the Pacific Cordillera of North America), Pinedale (in

612-558: The Last Glacial Maximum occurring between 26,000 and 20,000 years ago. While the general pattern of cooling and glacier advance around the globe was similar, local differences make it difficult to compare the details from continent to continent (see picture of ice core data below for differences). The most recent cooling, the Younger Dryas , began around 12,800 years ago and ended around 11,700 years ago, also marking

680-607: The Lesotho Highlands and parts of the Drakensberg . The development of glaciers was likely aided in part due to shade provided by adjacent cliffs. Various moraines and former glacial niches have been identified in the eastern Lesotho Highlands a few kilometres west of the Great Escarpment , at altitudes greater than 3,000 m on south-facing slopes. Studies suggest that the annual average temperature in

748-727: The Owen Stanley Range , and the Saruwaged Range . Mount Giluwe in the Central Cordillera had a "more or less continuous ice cap covering about 188 km and extending down to 3200-3500 m". In Western New Guinea , remnants of these glaciers are still preserved atop Puncak Jaya and Ngga Pilimsit . Small glaciers developed in a few favorable places in Southern Africa during the last glacial period. These small glaciers would have been located in

SECTION 10

#1732780359747

816-720: The Sierra Nevada in northern California . In northern Eurasia, the Scandinavian ice sheet once again reached the northern parts of the British Isles , Germany , Poland , and Russia, extending as far east as the Taymyr Peninsula in western Siberia. The maximum extent of western Siberian glaciation was reached by about 18,000 to 17,000 BP, later than in Europe (22,000–18,000 BP). Northeastern Siberia

884-732: The Upper Mississippi River , which in turn was formed during an earlier glacial period. In its retreat, the Wisconsin episode glaciation left terminal moraines that form Long Island , Block Island , Cape Cod , Nomans Land , Martha's Vineyard , Nantucket , Sable Island , and the Oak Ridges Moraine in south-central Ontario, Canada. In Wisconsin itself, it left the Kettle Moraine . The drumlins and eskers formed at its melting edge are landmarks of

952-584: The grooves left by these glaciers can be easily observed. In southwestern Saskatchewan and southeastern Alberta, a suture zone between the Laurentide and Cordilleran ice sheets formed the Cypress Hills , which is the northernmost point in North America that remained south of the continental ice sheets. The Great Lakes are the result of glacial scour and pooling of meltwater at the rim of

1020-586: The isostatically depressed area, a temporary marine incursion that geologists dub the Yoldia Sea . Then, as postglacial isostatic rebound lifted the region about 9500 BP, the deepest basin of the Baltic became a freshwater lake, in palaeological contexts referred to as Ancylus Lake , which is identifiable in the freshwater fauna found in sediment cores. The lake was filled by glacial runoff, but as worldwide sea level continued rising, saltwater again breached

1088-685: The 19th century, it was among the most important industrial centres along the North Shore. The first newspaper in the region, L'Écho du Labrador , was published in 1903 in Rivière-Pentecôte by Eudist father Joseph Laizé. In 1972 the Municipality of Rivière-Pentecôte was formed out of unorganized territory . On 19 February 2003 the Municipality of Rivière-Pentecôte was amalgamated into the Town of Port-Cartier. The Pentecôte River

1156-778: The Alpine foreland . Local ice fields or small ice sheets could be found capping the highest massifs of the Pyrenees , the Carpathian Mountains , the Balkan Mountains , the Caucasus , and the mountains of Turkey and Iran . In the Himalayas and the Tibetan Plateau , there is evidence that glaciers advanced considerably, particularly between 47,000 and 27,000 BP, but the exact ages, as well as

1224-745: The Center for Arctic Gas Hydrate, Environment and Climate at the University of Tromsø , published a study in June 2017 describing over a hundred ocean sediment craters, some 3,000 m wide and up to 300 m deep, formed by explosive eruptions of methane from destabilized methane hydrates , following ice-sheet retreat during the LGP, around 12,000 years ago. These areas around the Barents Sea still seep methane today. The study hypothesized that existing bulges containing methane reservoirs could eventually have

1292-696: The Goldthwait Sea was part of a broader process in what is now eastern Canada towards the end of the Last Glacial Period . The atmosphere was warmer near the oceans and towards the south, so melting of the Laurentide Ice Sheet progressed from east to west and from south to north. Around 12,000 years ago the Saint Lawrence Valley was opened to sea waters, The western arm of the Goldthwait Sea quickly extended up

1360-402: The Goldthwait Sea. Over the next 400 years the ice completely withdrew from the area, and the sea grew to its maximum size, with a coast parallel to the present coast but about 15 kilometres (9.3 mi) inland. Some fjords reached 70 kilometres (43 mi) further inland. The sea covered about 25,000 square kilometres (9,700 sq mi) of what is now Quebec, including Anticosti Island,

1428-598: The Greenland climate was dry during the LGP, with precipitation reaching perhaps only 20% of today's value. The name Mérida glaciation is proposed to designate the alpine glaciation that affected the central Venezuelan Andes during the Late Pleistocene. Two main moraine levels have been recognized - one with an elevation of 2,600–2,700 m (8,500–8,900 ft), and another with an elevation of 3,000–3,500 m (9,800–11,500 ft). The snow line during

SECTION 20

#1732780359747

1496-1010: The LGP as the Devensian . Irish geologists, geographers, and archaeologists refer to the Midlandian glaciation, as its effects in Ireland are largely visible in the Irish Midlands . The name Devensian is derived from the Latin Dēvenses , people living by the Dee ( Dēva in Latin), a river on the Welsh border near which deposits from the period are particularly well represented. The effects of this glaciation can be seen in many geological features of England, Wales, Scotland, and Northern Ireland . Its deposits have been found overlying material from

1564-498: The Laurentian Shield. The waters were still cold, but warmer and more saline than before. The third phase, lasting from 9,000 or 8,000 years ago until the present, was one of the sea slowly retreating. Isostatic recovery slowed to a few millimeters per year, but sea level rises were also small. Around 5,500 years ago the last of the ice sheet vanished from the center of Quebec. During this phase streams cut channels through

1632-868: The North American Laurentide ice sheet. At the height of glaciation, the Bering land bridge potentially permitted migration of mammals, including people, to North America from Siberia . It radically altered the geography of North America north of the Ohio River . At the height of the Wisconsin episode glaciation, ice covered most of Canada, the Upper Midwest , and New England , as well as parts of Montana and Washington . On Kelleys Island in Lake Erie or in New York's Central Park ,

1700-477: The North Atlantic Ocean during the deglaciation. Water was released from the glacial Lake St Lawrence around 11,000 years ago, and from the glacial Lake Agassiz between 10,900 and 9,900 years ago. Renewed warming caused run-off from the glacial Lake Agassiz and Lake Barlow-Ojibway between 9,500 and 8,000 years ago. The water seems to have flowed out into the ocean without mixing with the salt water in

1768-594: The Polish River Vistula or its German name Weichsel). Evidence suggests that the ice sheets were at their maximum size for only a short period, between 25,000 and 13,000 BP. Eight interstadials have been recognized in the Weichselian, including the Oerel, Glinde, Moershoofd, Hengelo, and Denekamp. Correlation with isotope stages is still in process. During the glacial maximum in Scandinavia, only

1836-565: The Saint Lawrence river and estuary. The bed of the Upper Saint Lawrence Estuary has glacial tills and bedrock covered by upwards of 200 metres (660 ft) of bluish-gray marine clays dating to the Goldthwait age. Three type of sediment can be seen along the Quebec coast. Silt and clay were deposited in deep water where river currents had no influence, deltaic sands were deposited where currents carried sediment into

1904-407: The Saint Lawrence, and this was followed by the Champlain Sea invasion. Three factors affected the area of the sea: the retreat of the ice sheet, isostatic rebound by the land and the rising sea level. The final retreat of the Laurentide Ice Sheet from eastern North America occurred between 12,000 and 10,000 years age. Freed from the pressure of the ice sheet, the land began to rise, and the shores of

1972-607: The Southern Hemisphere was less extensive. Ice sheets existed in the Andes ( Patagonian Ice Sheet ), where six glacier advances between 33,500 and 13,900 BP in the Chilean Andes have been reported. Antarctica was entirely glaciated, much like today, but unlike today the ice sheet left no uncovered area. In mainland Australia only a very small area in the vicinity of Mount Kosciuszko was glaciated, whereas in Tasmania glaciation

2040-452: The Wisconsin episode. It began about 30,000 years ago, reached its greatest advance 21,000 years ago, and ended about 10,000 years ago. In northwest Greenland, ice coverage attained a very early maximum in the LGP around 114,000. After this early maximum, ice coverage was similar to today until the end of the last glacial period. Towards the end, glaciers advanced once more before retreating to their present extent. According to ice core data,

2108-408: The average annual temperature is 1.9 °C (35.4 °F) and the average annual rainfall is 1,154 millimetres (45.4 in). In 1875 a mission called Saint-Patrice-de-la-Rivière-Pentecôte was established some 100 km south-west of Sept-Îles at the mouth of the Pentecôte River. In 1884, the Penticost River Post Office opened, renamed to the French form Rivière-Pentecôte in 1933. At the end of

Goldthwait Sea - Misplaced Pages Continue

2176-412: The depths of the Goldthwait Sea. The Goldthwait Sea, defined as the late-Glacial and post-Glacial invasion of the sea into Saint Lawrence estuary east of Quebec City and the Gulf of Saint Lawrence, began around 14,000 years ago. This was when the ice sheet was first withdrawn from the Gulf of Saint Lawrence. At that time the global sea level was about 55 metres (180 ft) lower than it is today. The sea

2244-400: The dramatic changes in the European environment during the Würm glaciation. During the height of Würm glaciation, c.  24,000  – c.  10,000  BP, most of western and central Europe and Eurasia was open steppe-tundra, while the Alps presented solid ice fields and montane glaciers. Scandinavia and much of Britain were under ice. During the Würm, the Rhône Glacier covered

2312-539: The end of the LGP and the Pleistocene epoch. It was followed by the Holocene , the current geological epoch . The LGP is often colloquially referred to as the "last ice age", though the term ice age is not strictly defined, and on a longer geological perspective, the last few million years could be termed a single ice age given the continual presence of ice sheets near both poles. Glacials are somewhat better defined, as colder phases during which glaciers advance, separated by relatively warm interglacials . The end of

2380-423: The formation of a single contiguous ice sheet on the Tibetan Plateau, is controversial. Other areas of the Northern Hemisphere did not bear extensive ice sheets, but local glaciers were widespread at high altitudes. Parts of Taiwan , for example, were repeatedly glaciated between 44,250 and 10,680 BP as well as the Japanese Alps . In both areas, maximum glacier advance occurred between 60,000 and 30,000 BP. To

2448-447: The last glacial advance was lowered approximately 1,200 m (3,900 ft) below the present snow line, which is 3,700 m (12,100 ft). The glaciated area in the Cordillera de Mérida was about 600 km (230 sq mi); this included these high areas, from southwest to northeast: Páramo de Tamá, Páramo Batallón, Páramo Los Conejos, Páramo Piedras Blancas, and Teta de Niquitao. Around 200 km (77 sq mi) of

2516-444: The last glacial maximum, the Patagonian ice sheet extended over the Andes from about 35°S to Tierra del Fuego at 55°S. The western part appears to have been very active, with wet basal conditions, while the eastern part was cold-based. Cryogenic features such as ice wedges , patterned ground , pingos , rock glaciers , palsas , soil cryoturbation , and solifluction deposits developed in unglaciated extra-Andean Patagonia during

2584-401: The last glacial period, which was about 10,000 years ago, is often called the end of the ice age, although extensive year-round ice persists in Antarctica and Greenland . Over the past few million years, the glacial-interglacial cycles have been "paced" by periodic variations in the Earth's orbit via Milankovitch cycles . The LGP has been intensively studied in North America, northern Eurasia,

2652-411: The last glaciation, but not all these reported features have been verified. The area west of Llanquihue Lake was ice-free during the last glacial maximum, and had sparsely distributed vegetation dominated by Nothofagus . Valdivian temperate rain forest was reduced to scattered remnants on the western side of the Andes. Rivi%C3%A8re-Pentec%C3%B4te Rivière-Pentecôte is a village on

2720-442: The late glacial (Weichselian) and the immediately preceding penultimate interglacial ( Eemian ) period. Canada was almost completely covered by ice, as was the northern part of the United States , both blanketed by the huge Laurentide Ice Sheet . Alaska remained mostly ice free due to arid climate conditions. Local glaciations existed in the Rocky Mountains and the Cordilleran ice sheet and as ice fields and ice caps in

2788-401: The lower Connecticut River Valley . In the Sierra Nevada , three stages of glacial maxima, sometimes incorrectly called ice ages , were separated by warmer periods. These glacial maxima are called, from oldest to youngest, Tahoe, Tenaya, and Tioga. The Tahoe reached its maximum extent perhaps about 70,000 years ago. Little is known about the Tenaya. The Tioga was the least severe and last of

Goldthwait Sea - Misplaced Pages Continue

2856-448: The main Wisconsin glacial advance. The upper level probably represents the last glacial advance (Late Wisconsin). The Llanquihue glaciation takes its name from Llanquihue Lake in southern Chile , which is a fan-shaped piedmont glacial lake. On the lake's western shores, large moraine systems occur, of which the innermost belong to the LGP. Llanquihue Lake's varves are a node point in southern Chile's varve geochronology . During

2924-430: The massive Missoula Floods . USGS geologists estimate that the cycle of flooding and reformation of the lake lasted an average of 55 years and that the floods occurred about 40 times over the 2,000-year period starting 15,000 years ago. Glacial lake outburst floods such as these are not uncommon today in Iceland and other places. The Wisconsin glacial episode was the last major advance of continental glaciers in

2992-502: The mountains of Southern Africa was about 6 °C colder than at present, in line with temperature drops estimated for Tasmania and southern Patagonia during the same time. This resulted in an environment of relatively arid periglaciation without permafrost , but with deep seasonal freezing on south-facing slopes. Periglaciation in the eastern Drakensberg and Lesotho Highlands produced solifluction deposits and blockfields ; including blockstreams and stone garlands. Scientists from

3060-415: The north shore of the Gulf of Saint Lawrence , part of the township of Port-Cartier . Rivière-Pentecôte is an administrative sector of the town of Port-Cartier , Sept-Rivières, Quebec. It is on the north shore of the Gulf of Saint Lawrence between Quebec Route 138 and the Pointe de la Rivière. The Riverin River flows through the town. The larger Pentecôte River enters the Saint Lawrence just south of

3128-461: The northeast. The difference can be partly accounted for by the ice cap having retreated earlier in the southern area, which would have rebounded further before the sea levels rose. There must have also been a thicker ice sheet further north, depressing the land further. The bed of the Goldthwait sea had inter-layered coarse sands and silty clays around its margins, and massive light gray fine clays further down. Rebound has exposed these sediments along

3196-463: The preceding Ipswichian stage and lying beneath those from the following Holocene , which is the current stage. This is sometimes called the Flandrian interglacial in Britain. The latter part of the Devensian includes pollen zones I–IV, the Allerød oscillation and Bølling oscillation , and the Oldest Dryas , Older Dryas , and Younger Dryas cold periods. Alternative names include Weichsel glaciation or Vistulian glaciation (referring to

3264-430: The proglacial rivers' shifting and redepositing gravels. Beneath the surface, they had profound and lasting influence on geothermal heat and the patterns of deep groundwater flow. The Pinedale (central Rocky Mountains) or Fraser (Cordilleran ice sheet) glaciation was the last of the major glaciations to appear in the Rocky Mountains in the United States. The Pinedale lasted from around 30,000 to 10,000 years ago, and

3332-410: The receding ice. When the enormous mass of the continental ice sheet retreated, the Great Lakes began gradually moving south due to isostatic rebound of the north shore. Niagara Falls is also a product of the glaciation, as is the course of the Ohio River, which largely supplanted the prior Teays River . With the assistance of several very broad glacial lakes, it released floods through the gorge of

3400-456: The region, so the sea reached the south and east of the area before it reached the west and north. To allow for regional variations in the timing of events, Dionne therefore proposes calling the phases Goldthwaitian I, II and III. In the first phase, lasting 500 to 1,500 years, the sea followed the retreating glacier front. The waters were cold and salinity low, and the sea was often ice-covered. The sea may have been prevented from entering some of

3468-399: The same fate. During the last glacial period, Antarctica was blanketed by a massive ice sheet, much as it is today. The ice covered all land areas and extended into the ocean onto the middle and outer continental shelf. Counterintuitively though, according to ice modeling done in 2002, ice over central East Antarctica was generally thinner than it is today. British geologists refer to

SECTION 50

#1732780359747

3536-458: The sea, and as the sea receded a blanket of coastal sand was deposited over both these types of sediment. Tidal flat clays are also found in some backwater areas of the sea. Last Glacial Period The Last Glacial Period ( LGP ), also known as the Last glacial cycle , occurred from the end of the Last Interglacial to the beginning of the Holocene , c.  115,000  – c.  11,700 years ago, and thus corresponds to most of

3604-425: The seas retreated. This post-glacial rebound (or isostatic rebound) continues today. Isostatic rebound was rapid at first, and 85% of the coastal area had emerged by 9,000 years ago. 13,000 years ago the rate of rebound was 3 centimetres (1.2 in) per year. Today it continues, but has slowed to 1 millimetre (0.039 in) per year. Large amounts of fresh water, including melted ice and precipitation, flowed into

3672-400: The sediments laid down in the previous phase. The Goldthwait Sea began to form in the Saint Lawrence Estuary and Gulf around 13,500 years ago. By 9,300 years age the ice front had retreated about 8 kilometres (5.0 mi) from the present shoreline in the north coast region between Rivière-Pentecôte and Sept-Îles , as shown by a belt of end moraines. The present coastal plain was covered by

3740-413: The sill about 8000 BP, forming a marine Littorina Sea , which was followed by another freshwater phase before the present brackish marine system was established. "At its present state of development, the marine life of the Baltic Sea is less than about 4000 years old", Drs. Thulin and Andrushaitis remarked when reviewing these sequences in 2003. Overlying ice had exerted pressure on the Earth's surface. As

3808-414: The south of the Saint Lawrence between Lévis and Baie-Saint-Paul , and the north shore between Les Escoumins and Blanc-Sablon . Many shorelines can be seen at different elevations in the area that was once submerged. The limit of land once covered by the Goldthwait Sea varies from 100 metres (330 ft) above the present sea level at Godbout, Quebec to 130 metres (430 ft) at Sept-Îles further to

3876-428: The surrounding ice sheets. According to the sediment composition retrieved from deep-sea cores , even times of seasonally open waters must have occurred. Outside the main ice sheets, widespread glaciation occurred on the highest mountains of the Alpide belt . In contrast to the earlier glacial stages, the Würm glaciation was composed of smaller ice caps and mostly confined to valley glaciers, sending glacial lobes into

3944-405: The term Late Cenozoic Ice Age is used to include this early phase with the current glaciation. The previous ice age within the Quaternary is the Penultimate Glacial Period , which ended about 128,000 years ago, was more severe than the Last Glacial Period in some areas such as Britain, but less severe in others. The last glacial period saw alternating episodes of glacier advance and retreat with

4012-449: The timespan of the Late Pleistocene . The LGP is part of a larger sequence of glacial and interglacial periods known as the Quaternary glaciation which started around 2,588,000 years ago and is ongoing. The glaciation and the current Quaternary Period both began with the formation of the Arctic ice cap . The Antarctic ice sheet began to form earlier, at about 34 Mya, in the mid- Cenozoic ( Eocene–Oligocene extinction event ), and

4080-447: The total glaciated area was in the Sierra Nevada de Mérida , and of that amount, the largest concentration, 50 km (19 sq mi), was in the areas of Pico Bolívar , Pico Humboldt [4,942 m (16,214 ft)], and Pico Bonpland [4,983 m (16,348 ft)]. Radiocarbon dating indicates that the moraines are older than 10,000 BP, and probably older than 13,000 BP. The lower moraine level probably corresponds to

4148-406: The valleys by lingering ice. Isostatic recovery began in this phase. In the second phase, lasting for 2,000 to 3,000 years, the sea first advanced and then retreated. During this phase isostatic uplift was rapid, but sea levels were also rising. There was much sedimentation along the shoreline, with deltas formed at the mouths of the main rivers on the north shore fed by meltwater from the ice sheet on

SECTION 60

#1732780359747

4216-462: The village. This name is attributed to Jacques Cartier , who arrived in the area on the Christian holy day of Pentecost in 1535. Pentecôte is French for Pentecost. There is a reference to the river in a document by Louis Jolliet from 1685 in which he refers to a river named "Pannecoste". The Pentecôte weather station is operated by the Ministry of Sustainable Development, Environment, and Fight Against Climate Change (MDDELCC). It reports that

4284-435: The western parts of Jutland were ice-free, and a large part of what is today the North Sea was dry land connecting Jutland with Britain (see Doggerland ). The Baltic Sea , with its unique brackish water , is a result of meltwater from the Weichsel glaciation combining with saltwater from the North Sea when the straits between Sweden and Denmark opened. Initially, when the ice began melting about 10,300 BP, seawater filled

4352-523: The whole western Swiss plateau, reaching today's regions of Solothurn and Aargau. In the region of Bern, it merged with the Aar glacier. The Rhine Glacier is currently the subject of the most detailed studies. Glaciers of the Reuss and the Limmat advanced sometimes as far as the Jura. Montane and piedmont glaciers formed the land by grinding away virtually all traces of the older Günz and Mindel glaciation, by depositing base moraines and terminal moraines of different retraction phases and loess deposits, and by

4420-412: Was able to cover the coastal areas of the Saint Lawrence because the land had subsided under the burden of the ice sheet. After this, sea levels gradually rose as water from the ice sheet was returned to the ocean, but at the same time the land rebounded, causing a complex sequence of submersion. There were two main phases, a short phase of sea invasion as soon as the ice sheet moved back from the coast, and

4488-404: Was at its greatest extent between 23,500 and 21,000 years ago. This glaciation was somewhat distinct from the main Wisconsin glaciation, as it was only loosely related to the giant ice sheets and was instead composed of mountain glaciers, merging into the Cordilleran ice sheet. The Cordilleran ice sheet produced features such as glacial Lake Missoula , which broke free from its ice dam, causing

4556-405: Was more widespread. An ice sheet formed in New Zealand, covering all of the Southern Alps, where at least three glacial advances can be distinguished. Local ice caps existed in the highest mountains of the island of New Guinea , where temperatures were 5 to 6 °C colder than at present. The main areas of Papua New Guinea where glaciers developed during the LGP were the Central Cordillera ,

4624-432: Was not covered by a continental-scale ice sheet. Instead, large, but restricted, icefield complexes covered mountain ranges within northeast Siberia, including the Kamchatka-Koryak Mountains. The Arctic Ocean between the huge ice sheets of America and Eurasia was not frozen throughout, but like today, probably was covered only by relatively shallow ice, subject to seasonal changes and riddled with icebergs calving from

#746253