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"Last glacial" redirects here. For the period of maximum glacier extent during this time see Last Glacial Maximum
The last glacial period was the most recent glacial period within the current ice age, occurring in the Pleistocene epoch. It began about 110,000 years ago and ended about 9,600 - 9,700 BC. During this period there were several changes between glacier advance and retreat. The maximum extent of glaciation was approximately 18,000 years ago. While the general pattern of global cooling and glacier advance was similar, local differences in the development of glacier advance and retreat make it difficult to compare the details from continent to continent (see picture of ice core data below for differences).

The last glacial period is sometimes colloquially referred to as the "last ice age", though this use is incorrect because an ice age is a longer period of cold temperature in which ice sheets cover large parts of the Earth, such as Antarctica. Glacials, on the other hand, refer to colder phases within an ice age that separate interglacials. Thus, the end of the last glacial period is not the end of the last ice age. The end of the last glacial period was about 12,500 years ago, while the end of the last ice age may not yet have come: little evidence points to a stop of the glacial-interglacial cycle of the last million years.

The last glacial period is the best-known part of the current ice age, and has been intensively studied in North America, northern Eurasia, the Himalaya and other formerly glaciated regions around the world. The glaciations that occurred during this glacial period covered many areas, mainly on the Northern Hemispheremarker and to a lesser extent on the Southern Hemispheremarker. They have different names, historically developed and depending on their geographic distributions: Fraser (in the Pacific Cordillera of North America), Pinedale, Wisconsinan or Wisconsin (in central North America), Devensian (in the British Islesmarker), Midlandian (in Irelandmarker), Würm (in the Alps), Merida (in Venezuelamarker), Weichselian (in Scandinavia and Northern Europe), Vistulian (in northern Central Europe), Valdai in Eastern Europe and Zyryanka in Siberiamarker, Llanquihue in Chilemarker, and Otira in New Zealandmarker.

Overview



The last glaciation centered on the huge ice sheets of North America and Eurasia. Considerable areas in the Alps, the Himalaya and the Andes were ice-covered, and Antarctica remained glaciated.

Canada was nearly completely covered by ice, as well as the northern part of the USA, 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, the Cordilleran ice sheet and as ice fields and ice caps in the Sierra Nevada in northern California. In Britainmarker, mainland Europe and northwestern Asia, the Scandinavian ice sheet once again reached the northern parts of the British Isles, Germanymarker, Polandmarker and Russiamarker, extending as far east as the Taimyr Peninsulamarker in western Siberia. Maximum extent of western Siberian glaciation was approximately 18,000 to 17,000 BP and thus later than in Europe (22,000–18,000 BP). Northeastern Siberia 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 Oceanmarker between the huge ice sheets of America and Eurasia was not frozen throughout, but like today probably was only covered by relatively thin ice, subject to seasonal changes and riddled with icebergs calving from the surrounding ice sheets. According to the sediment composition retrieved from deep-sea cores there must even have been times of seasonally open waters.

Outside the main ice sheets widespread glaciation occurred on the Alps-Himalayamarker mountain chain. 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 the Alpine forland. To the east the Caucasus and the mountains of Turkeymarker and Iranmarker were capped by local ice fields or small ice sheets.,In the Himalayamarker and the Tibetan Plateaumarker glaciers advanced considerably, particularly between 47,000–27,000 BP and in contrast to the widespread contemporaneous warming elsewhere. The formation of a contiguous ice sheet on the Tibetan Plateau is controversial.

Other areas of the Northern Hemisphere did not bear extensive ice sheets but local glaciers in high areas. Parts of Taiwanmarker for example were repeatedly glaciated between 44,250 and 10,680 BP as well as the Japanese Alpsmarker. In both areas maximum glacier advance occurred between 60,000 and 30,000 BP. To a still lesser extent glaciers existed in Africa, for example in the High Atlasmarker, the mountains of Moroccomarker, the Mount Atakor massif in southern Algeriamarker and several mountains in Ethiopiamarker. In the Southern Hemisphere, an ice cap of several hundred square kilometers was present on the east African mountains in the Kilimanjaromarker Massif, Mount Kenyamarker and the Ruwenzori Mountainsmarker, still bearing remnants of glaciers today.

Glaciation of the Southern Hemisphere was less extensive because of current configuration of continents. 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. Antarcticamarker was entirely glaciated, much like today, but the ice sheet left no uncovered area. In mainland Australia only a very small area in the vicinity of Mount Kosciuszkomarker was glaciated, whereas in Tasmaniamarker glaciation was more widespread. New Zealandmarker saw a glaciation in the New Zealand Alps, where at least three glacier advances can be distinguished. Local ice caps existed in Irian Jayamarker, Indonesiamarker, where in three ice areas remnants of the Pleistocene glaciers are still preserved today.

Named local glaciations

Pinedale or Fraser glaciation, in the Rocky Mountains, USA

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 approximately 30,000 to 10,000 years ago and 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 Missoulamarker, which would break free from its ice dam causing the massive Missoula floods. Geologists estimate that the cycle of flooding and reformation of the lake lasted on average of 55 years and that the floods occurred approximately 40 times over the 2,000 year period between 15,000 and 13,000 years ago. Glacial lake outburst floods such as these are not uncommon today in Icelandmarker and other places.

Wisconsin glaciation, in North America

The Wisconsin Glacial Episode was the last major advance of continental glaciers in the North American Laurentide ice sheet. This glaciation is made of three glacial maxima (sometimes mistakenly called ice ages) separated by interglacial warm periods (such as the one we are living in). 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, perhaps as a byproduct of the Toba super eruptionmarker. Little is known about the Tenaya. The Tioga was the least severe and last of 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. At the height of glaciation the Bering land bridge permitted migration of mammals such as humans 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 Canadamarker, the Upper Midwest, and New Englandmarker, as well as parts of Montanamarker and Washingtonmarker. On Kelleys Islandmarker in Lake Eriemarker or in New York's Central Parkmarker, 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 Hillsmarker, which is the northernmost point in North America that remained south of the continental ice sheets.

The Great Lakesmarker are the result of glacial scour and pooling of meltwater at the rim of 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 Fallsmarker 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 large glacial lakes, it carved the gorge now known as the Upper Mississippi River, filling into the Driftless Area and probably creating an annual ice-dam-burst.

In its retreat, the Wisconsin Episode glaciation left terminal moraines that form Long Islandmarker, Block Islandmarker, Cape Codmarker, Nomans Landmarker, Marthas Vineyardmarker, and Nantucketmarker, 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 the Lower Connecticut River Valley.

Greenland glaciation

In Northwest Greenland, ice coverage attained a very early maximum in the last glacial period around 114,000. After this early maximum, the ice coverage was similar to today until the end of the last glacial period. Towards the end glaciers readvanced once more before retreating to their present extent. According to ice core data, the Greenland climate was dry during the last glacial period, precipitation reaching perhaps only 20% of today's value.

Devensian & Midlandian glaciation, in Britain and Ireland

The name Devensian glaciation is used by British geologists and archaeologists and refers to what is often popularly meant by the latest Ice Age. Irish geologists, geographers and archaeologists refer to the Midlandian glaciation as its effects in Irelandmarker are largely visible in the midlands.

The effects of this glaciation can be seen in many geological features of Englandmarker, Walesmarker, Scotlandmarker, and Northern Irelandmarker. Its deposits have been found overlying material from the preceding Ipswichian Stage and lying beneath those from the following Flandrian stage of the Holocene.

The latter part of the Devensian includes Pollen zones I-IV, the Allerød, and Bølling Oscillations and the Older and Younger Dryas climatic stages.

Weichselian glaciation, in Scandinavia and northern Europe

Alternative names include: Weichsel or Vistulian glaciation (named after the Polish river Vistula or its German name Weichsel). During the glacial maximum in Scandinavia, only the western parts of Jutland were ice-free, and a large part of what is today the North Seamarker was dry land connecting Jutland with Britain. It is also in Denmark that the only Scandinavian ice-age animals older than 13,000 BC are found. In the period following the last interglacial before the current one (Eemian Stage), the coast of Norwaymarker was also ice-free.

The Baltic Seamarker, 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 ybp, seawater filled the isostatically depressed area, a temporary marine incursion that geologists dub the Yoldia Sea. Then, as post-glacial isostatic rebound lifted the region about 9500 ybp, 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 the sill about 8000 ybp, 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.

Overlaying ice had exerted pressure on the Earth's surface. As a result of melting ice, the land has continued to rise yearly in Scandinavia, mostly in northern Swedenmarker and Finlandmarker where the land is rising at a rate of as much as 8–9 mm per year, or 1 meter 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.

Würm glaciation, in the Alps

The term Würmmarker is derived from a river in the Alpine foreland, approximately marking the maximum glacier advance of this particular glacial period. The Alps have been the area where first systematic scientific research on ice ages has been conducted by Louis Agassiz in the beginning of the 19th century. Here the Würm glaciation of the last glacial period was intensively studied. Pollen analysis, the statistical analyses of microfossilized plant pollens found in geological deposits, has chronicled the dramatic changes in the European environment during the Würm glaciation. During the height of Würm glaciation, ca 24,000–10,000 ybp, 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 Glaciermarker covered the whole western Swiss plateau, reaching today's regions of Solothurn and Aarau. 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 the pro-glacial rivers' shifting and redepositing gravels. Beneath the surface, they had profound and lasting influence on geothermal heat and the patterns of deep groundwater flow.

Merida glaciation, in the Venezuelan Andes

The name Merida Glaciation is proposed to designate the alpine glaciation which affected the central Venezuelan Andesmarker; during the Late Pleistocene. Two main moraine levels have been recognized: one between 2600 and 2700 m, and another between 3000 and 3500 m elevation. The snow line during the last glacial advance was lowered approximately 1200 m below the present snow line (3700 m). The glaciated area in the Cordillera de Méridamarker was approximately 600 km2; this included the following high areas from southwest to northeast: Páramo de Tamá, Páramo Batallón, Páramo Los Conejos, Páramo Piedras Blancas, and Teta de Niquitao. Approximately 200 km2 of the total glaciated area was in the Sierra Nevada de Mérida, and of that amount, the largest concentration, 50 km2, was in the areas of Pico Bolívarmarker, Pico Humboldtmarker (4,942 m), and Pico Bonplandmarker (4,893 m). Radiocarbon dating indicates that the moraines are older than 10,000 years B.P., and probably older than 13,000 years B.P. The lower moraine level probably corresponds to the main Wisconsin glacial advance. The upper level probably represents the last glacial advance (Late Wisconsin).

Llanquihue glaciation, southern Andes

The Llanquihue glaciation takes its name from Llanquihue Lakemarker in southern Chile which is a fan-shaped piedmont glacial lake. On the lake's western shores there are large moraine systems of which the innermost belong to the last glacial period. Llanquihue Lake's varves are a node point in southern Chile's varve geochronology. During the last glacial maximum the Patagonian Ice Sheet extended over the Andes from about 35°S to Tierra del Fuegomarker at 55°S. The western part appears to have been very active, with wet basal conditions, while the eastern part was cold based. Palsas seems to have developed at least in the unglaciated parts of Isla Grande de Tierra del Fuegomarker. The area west of Llanquihue Lake was ice-free during the LGM, and had sparcely distributed vegetation dominated by Nothofagus. Valdivian temperate rainforest extended continuously as far north as to Bosque de Fray Jorge National Parkmarker, the forest currently found there are relicts from the Last glacial period.

Antarctica glaciation

Modelled maximum extent of the Antarctic ice sheet 21,000 years before present


During the last glacial period Antarcticamarker was blanketed by a massive ice sheet, much like it is today. The ice covered all land areas and extended into the ocean onto the middle and outer continental shelf. According to ice modelling, ice over central East Antarctica was generally thinner than today.

References

  1. Clark, D.H.: Extent, timing, and climatic significance of latest Pleistocene and Holocene glaciation in the Sierra Nevada, California. Ph.D. Thesis, Washington Univ., Seattle (pdf, 20 Mb)
  2. Möller, P. et al.: Severnaya Zemlya, Arctic Russia: a nucleation area for Kara Sea ice sheets during the Middle to Late Quaternary. Quaternary Science Reviews Vol. 25, No. 21–22, pp. 2894–2936, 2006. (pdf, 11.5 Mb)
  3. Matti Saarnisto: Climate variability during the last interglacial-glacial cycle in NW Eurasia. Abstracts of PAGES - PEPIII: Past Climate Variability Through Europe and Africa, 2001
  4. Lyn Gualtieri et al.: Pleistocene raised marine deposits on Wrangel Island, northeast Siberia and implications for the presence of an East Siberian ice sheet. Quaternary Research, Vol. 59, No. 3, pp. 399-410, May 2003. Abstract:
  5. Zamoruyev, V., 2004. Quaternary glaciation of north-east Asia. In: Ehlers, J., Gibbard, P.L. (Eds.), Quaternary Glaciations: Extent and Chronology: Part III: South America, Asia, Africa, Australia, Antarctica. Elsevier, Netherlands, pp. 321–323.
  6. Robert F. Spielhagen et al.: Arctic Ocean deep-sea record of northern Eurasian ice sheet history. Quaternary Science Reviews, Vol. 23, No. 11-13, pp. 1455-1483, 2004. Abstract:
  7. Richard S. Williams, Jr., Jane G. Ferrigno: Glaciers of the Middle East and Africa - Glaciers of Turkey. U.S.Geological Survey Professional Paper 1386-G-1, 1991 (pdf, 2.5 Mb)
  8. Jane G. Ferrigno: Glaciers of the Middle East and Africa - Glaciers of Iran. U.S.Geological Survey Professional Paper 1386-G-2, 1991 (pdf, 1.25 Mb)
  9. Lewis A. Owen et al.: A note on the extent of glaciation throughout the Himalaya during the global Last Glacial Maximum, Quaternary Science Reviews, V. 21, No. 1, 2002, pp. 147-157. Abstract:
  10. Quaternary stratigraphy: The last glaciation (stage 4 to stage 2), University of Otago, New Zealand
  11. Lehmkuhl, F.: Die eiszeitliche Vergletscherung Hochasiens - lokale Vergletscherungen oder übergeordneter Eisschild? Geographische Rundschau 55 (2):28-33, 2003. English abstract
  12. Zhijiu Cui et al.: The Quaternary glaciation of Shesan Mountain in Taiwan and glacial classification in monsoon areas. Quaternary International, Vol. 97-98, pp. 147-153, 2002. Abstract:
  13. Yugo Ono et al.: Mountain glaciation in Japan and Taiwan at the global Last Glacial Maximum. Quaternary International, Vol. 138-139, pp. 79-92, September-October 2005. Abstract:
  14. James A.T. Young, Stefan Hastenrath: Glaciers of the Middle East and Africa - Glaciers of Africa. U.S.Geological Survey Professional Paper 1386-G-3, 1991 (pdf, 1.25 Mb)
  15. Lowell, T.V. et al.: Interhemisperic correlation of late Pleistocene glacial events, Science, v. 269,p. 1541-1549, 1995. Abstract (pdf, 2.3 Mb)
  16. C.D. Ollier: Australian Landforms and their History, National Mapping Fab, Geoscience Australia
  17. A mid Otira Glaciation palaeosol and flora from the Castle Hill Basin, Canterbury, New Zealand, New Zealand Journal of Botany. Vol. 34, pp. 539-545, 1996 (pdf, 340 Kb)
  18. Ian Allison and James A. Peterson: Glaciers of Irian Jaya, Indonesia: Observation and Mapping of the Glaciers Shown on Landsat Images, U.S. Geological Survey professional paper; 1386, 1988. ISBN 0-607-71457-3
  19. Brief geologic history, Rocky Mountain National Park
  20. Ice Age Floods, From: U.S. National Park Service Website
  21. Richard B. Waitt, Jr.: Case for periodic, colossal jökulhlaups from Pleistocene glacial Lake Missoula, Geological Society of America Bulletin, v.96, p.1271-1286, October 1985. Abstract
  22. Svend Funder (ed.) Late Quaternary stratigraphy and glaciology in the Thule area, Northwest Greenland. MoG Geoscience, vol. 22, 63 pp., 1990. Abstract
  23. Sigfus J. Johnsen et al.: A "deep" ice core from East Greenland. MoG Geoscience, vol. 29, 22 pp., 1992. Abstract
  24. * Schubert, Carlos (1998) "Glaciers of Venezuela" United States Geological Survey (USGS P 1386-I)
  25. Late Pleistocene glaciation of Páramo de La Culata, north-central Venezuelan Andes
  26. Mahaney William C., Milner M. W., Kalm Volli, Dirsowzky Randy W., Hancock R. G. V., Beukens Roelf P.: Evidence for a Younger Dryas glacial advance in the Andes of northwestern Venezuela
  27. Maximiliano B., Orlando G., Juan C., Ciro S.: Glacial Quaternary geology of las Gonzales basin, páramo los conejos, Venezuelan andes
  28. Anderson, J.B., S.S. Shipp, A.L. Lowe, J.S. Wellner, J.S., and A.B. Mosola, 2002, The Antarctic Ice Sheet during the Last Glacial Maximum and its subsequent retreat history: a review. Quaternary Science Reviews. vol. 21, pp. 49-70.
  29. Ingolfsson, O., 2004, Quaternary glacial and climate history of Antarctica. in: J. Ehlers and P.L. Gibbard, eds., pp. 3-43, Quaternary Glaciations: Extent and Chronology 3: Part III: South America, Asia, Africa, Australia, Antarctica. Elsevier, New York.
  30. P. Huybrechts: Sea-level changes at the LGM from ice-dynamic reconstructions of the Greenland and Antarctic ice sheets during the glacial cycles, Quaternary Science Reviews, V. 21, no. 1-3, pp. 203-231, 2002. Abstract:


Further reading

  • Bowen, D.Q., 1978, Quaternary geology: a stratigraphic framework for multidisciplinary work. Pergamon Press, Oxford, United Kingdom. 221 pp. ISBN 978-0080204093
  • Ehlers, J., and P.L. Gibbard, 2004a, Quaternary Glaciations: Extent and Chronology 2: Part II North America. Elsevier, Amsterdam. ISBN 0-444-51462-7
  • Ehlers, J., and P L. Gibbard, 2004b, Quaternary Glaciations: Extent and Chronology 3: Part III: South America, Asia, Africa, Australia, Antarctica. ISBN 0-444-51593-3
  • Gillespie, A.R., S.C. Porter, and B.F. Atwater, 2004, The Quaternary Period in the United States. Developments in Quaternary Science no. 1. Elsevier, Amsterdam. ISBN 978-0-444-51471-4
  • Harris, A.G., E. Tuttle, S.D. Tuttle, 1997, Geology of National Parks: Fifth Edition. Kendall/Hunt Publishing, Iowa. ISBN 0-7872-5353-7
  • Mangerud, J., J. Ehlers, and P. Gibbard, 2004, Quaternary Glaciations : Extent and Chronology 1: Part I Europe. Elsevier, Amsterdam. ISBN 0-444-51462-7
  • Sibrava, V., Bowen, D.Q, and Richmond, G.M., 1986, Quaternary Glaciations in the Northern Hemisphere, Quaternary Science Reviews. vol. 5, pp. 1-514.
  • Pielou, E.C., 1991. After the Ice Age : The Return of Life to Glaciated North America. University Of Chicago Press, Chicago, Illinois. ISBN 0-226-66812-6 (paperback 1992)


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