Last Glacial Period

[1] 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.

Glacials are somewhat better defined, as colder phases during which glaciers advance, separated by relatively warm interglacials.

The LGP has been intensively studied in North America, northern Eurasia, the Himalayas, and other formerly glaciated regions around the world.

They have different names, historically developed and depending on their geographic distributions: Fraser (in the Pacific Cordillera of North America), Pinedale (in the Central Rocky Mountains), Wisconsinan or Wisconsin (in central North America), Devensian (in the British Isles),[5] 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.

[17][18][19] Other areas of the Northern Hemisphere did not bear extensive ice sheets, but local glaciers were widespread at high altitudes.

[25] 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.

[31] 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.

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.

[28][29] Scientists from the Center for Arctic Gas Hydrate, Environment and Climate at the University of Tromsø, published a study in June 2017[32] 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.

Initially, when the ice began melting about 10,300 BP, seawater filled the isostatically depressed area, a temporary marine incursion that geologists dub the Yoldia Sea.

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 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.

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.

During the Würm, the Rhône Glacier covered the whole western Swiss plateau, reaching today's regions of Solothurn and Aargau.

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 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 Wisconsin glacial episode was the last major advance of continental glaciers in 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.

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, the grooves left by these glaciers can be easily observed.

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.

In the Sierra Nevada, three stages of glacial maxima, sometimes incorrectly called ice ages, were separated by warmer periods.

After this early maximum, ice coverage was similar to today until the end of the last glacial period.

During the last glacial maximum, the Patagonian ice sheet extended over the Andes from about 35°S to Tierra del Fuego at 55°S.

[50] The area west of Llanquihue Lake was ice-free during the last glacial maximum, and had sparsely distributed vegetation dominated by Nothofagus.