The

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

glacial retreat is a geographical phenomenon that involved the global retreat of glaciers (

deglaciation Deglaciation is the transition from full glacial conditions during ice ages, to warm interglacials, characterized by global warming and sea level rise due to change in continental ice volume. Thus, it refers to the retreat of a glacier, an ice shee ...

) that previously had advanced during the

Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eu ...

. Ice sheet retreat initiated ca. 19,000 years ago and accelerated after ca. 15,000 years ago. The

, starting with abrupt warming 11,700 years ago, resulted in rapid melting of the remaining ice sheets of North America and Europe.

Geographical alterations

Antarctica

Fragments_of_Larsen_B_Ice_Shelf_Lingered_Until_2005

Radiocarbon dating has been used to date the start of glacial retreat on Alexander island 18,000 years ago. The outermost locations like Marguerite Bay were fully deglaciated 12,000 years ago and the further inland locations continued deglaciating for an additional 3,000 years. The Larsen ice shelf was formed in the early Holocene at a latest estimation of 10,700 years ago. Certain segments of the ice shelf have collapsed as recently as 1995 for Larsen A and a large segment of Larsen B collapsed in 2002.

Europe

The many valleys of the

Cairngorms The Cairngorms ( gd, Am Monadh Ruadh) are a mountain range in the eastern Highlands of Scotland closely associated with the mountain Cairn Gorm. The Cairngorms became part of Scotland's second national park (the Cairngorms National Park) on 1 S ...

, a mountainous region in the Eastern

Scottish Highlands The Highlands ( sco, the Hielands; gd, a’ Ghàidhealtachd , 'the place of the Gaels') is a historical region of Scotland. Culturally, the Highlands and the Lowlands diverged from the Late Middle Ages into the modern period, when Lowland S ...

are littered with deposits from this period. In northwestern Iceland, the Icelandic ice sheet began its non-uniform retreat about 15,000 years ago. Surface exposure dating using the

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass num ...

³⁶Cl was the primary means of dating boulders and

terminal moraine A terminal moraine, also called end moraine, is a type of moraine that forms at the terminal (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, has been pushed by the front edge ...

s in the

Drangajökull Drangajökull (, regionally also ) is the northernmost glacier of Iceland. It is situated southwest of the peninsula Hornstrandir in the Westfjords region. The glacier covers an area of , at an altitude of up to . It is the only Icelandic glacier ...

area in Iceland. Ages of erratic boulders found near the Leirufjörður valley and moraine range from 7-12 thousand years old. The average ages for the groupings of boulders in the Leirufjörður area is 9.3 thousand years ago. Directly south of Leirufjörður in the Kaldalon Valley the average age of the boulders is 15,000 years old. The two different average ages are a result of different rates of glacial activity in Iceland. Glacier Mass Balance Map

Another area that has experienced deglaciation during the Holocene is

Spitsbergen Spitsbergen (; formerly known as West Spitsbergen; Norwegian: ''Vest Spitsbergen'' or ''Vestspitsbergen'' , also sometimes spelled Spitzbergen) is the largest and the only permanently populated island of the Svalbard archipelago in northern Nor ...

island within the

Svalbard Svalbard ( , ), also known as Spitsbergen, or Spitzbergen, is a Norwegian archipelago in the Arctic Ocean. North of mainland Europe, it is about midway between the northern coast of Norway and the North Pole. The islands of the group rang ...

archipelago in Norway. For the last 12,000 years exposed rockwalls have been eroding due to a mixture of biogenic flaking, frost shattering, and stress relaxation that results when glaciers retreat. One way the rate of rockwall retreat is measured is by examining the diameters of local lichen to establish an age of growth.

North America

The retreat of the

Laurentide Ice Sheet The Laurentide Ice Sheet was a massive sheet of ice that covered millions of square miles, including most of Canada and a large portion of the Northern United States, multiple times during the Quaternary glacial epochs, from 2.58 million year ...

in Canada led to the formation of moraines and up to 26

proglacial lakes In geology, a proglacial lake is a lake formed either by the damming action of a moraine during the retreat of a melting glacier, a glacial ice dam, or by meltwater trapped against an ice sheet due to isostatic depression of the crust around the ...

scattered throughout central Canada. The deglaciation occurred from the last glacial maximum (21,000 years ago) until about 7000 years ago. Some of the lakes in the southern Ungava Bay area were fully deglaciated c. 6,000 years ago. Meltwater from the glacial prehistoric

Lake Agassiz Lake Agassiz was a large glacial lake in central North America. Fed by glacial meltwater at the end of the last glacial period, its area was larger than all of the modern Great Lakes combined. First postulated in 1823 by William H. Keating, i ...

contributed to the neoglaciation during the Holocene, which resulted in an uptick of glacial activity at least as far away as Iceland. The

Nuup Kangerlua Nuup Kangerlua is a long fjord in the Sermersooq municipality in southwestern Greenland. It was formerly known by its colonial name as Godthaab Fjord ( da, Godthåbsfjorden), Gilbert Sound and Baal's River.Nicoll, James. An Historical and Descr ...

and

Sermilik Sermilik ( da, Egede og Rothes Fjord) is a fjord in eastern Greenland. It is part of the Sermersooq municipality. The settlement of Tasiilaq is located about 15 km to the east of the mouth of the fjord. Geography This fjord, whose Gre ...

regions, in southwestern and southeastern

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland ...

respectively, are two localities that experienced deglaciation after the Holocene warming period started. Warming atmospheric temperatures as well as warming waters in the

Labrador Sea The Labrador Sea (French: ''mer du Labrador'', Danish: ''Labradorhavet'') is an arm of the North Atlantic Ocean between the Labrador Peninsula and Greenland. The sea is flanked by continental shelves to the southwest, northwest, and northeast. It ...

accelerated the speed of deglaciation which started on the coasts of Greenland before heading inland. Moraines located in the interior of the Nuup Kangerlua area have been dated to 8.1 to 8.3 thousand years ago; they mark a local cooling that caused glaciers to re-advance and leave moraines behind. The modern

Ohio River The Ohio River is a long river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing southwesterly from western Pennsylvania to its mouth on the Mississippi River at the southern tip of ...

was formed when the river was temporarily dammed just southwest of

Louisville, Kentucky Louisville ( , , ) is the largest city in the Commonwealth of Kentucky and the 28th most-populous city in the United States. Louisville is the historical seat and, since 2003, the nominal seat of Jefferson County, on the Indiana border ...

, creating a large lake until the dam burst. The Ohio River largely supplanted the former Teays River drainage system, which was disrupted by the glaciers. Ancient

Lake Chicago Lake Chicago was a prehistoric proglacial lake that is the ancestor of what is now known as Lake Michigan, one of North America's five Great Lakes. Fed by retreating glaciers, it drained south through the Chicago Outlet River. Origin The ...

, on the southern margin of the Wisconsin Glacier, found successive lower outlets as the glacier retreated, until the

Saint Lawrence River The St. Lawrence River (french: Fleuve Saint-Laurent, ) is a large river in the middle latitudes of North America. Its headwaters begin flowing from Lake Ontario in a (roughly) northeasterly direction, into the Gulf of St. Lawrence, connecting ...

route was uncovered. Corresponding to each level, remnant lake shore features may be found in many areas. One prehistoric shoreline is delineated by Bluff Avenue, a north–south street on the

La Grange, Illinois ''(the barn)'' , nickname = , motto = ''Tradition & Pride – Moving Forward'' , anthem = ''My La Grange'' by Jimmy Dunne , image_map = File:Cook County Illinois Incorporated and Unincorporated areas La Grange Highlighted.svg , mapsize = 26 ...

, east side. Current river delta positioning and sediment composition in northern Michigan were created by a glacial lake. The lake resulted from retreating glaciers.

South America

The Northern Patagonian Icefield is one of the locations that experienced a surge in glacial activity during the neoglaciation period. Terminal moraines formed 5.7 thousand years ago in the San Rafael Glacier and around 4.96 thousand years ago they formed in the nearby Colonia glacier. In the Southern Patagonian Icefield located in Argentina and Chile, some glaciers have actually been advancing to their peak extents as recently as the 19th century as evidenced by moraines. Another remnant of glacial activity in the southern Patagonian icefield is the creation of meltwater channels within the El Canal spillway found near the Lago del Toro in Chile. The different layers of stratification have been used to date different occurrences of glacial lakes in the region.

New Zealand

Within the last 30 years while most locations have experienced continue glacial retreat, glaciers located in the Southern Alps of New Zealand have advanced in position. Glaciers located near coasts such as those in New Zealand are especially responsive to climate change and serve as an indicator of local climate change. The anticipated warming waters near New Zealand in the Tasman Sea will lead to a reduction in glacial mass balance.

References

{{Reflist, 33em

External links

The Post-Glacial Period Holocene Epoch

Glacial retreat The retreat of glaciers since 1850 affects the availability of fresh water for irrigation and domestic use, mountain recreation, animals and plants that depend on glacier-melt, and, in the longer term, the level of the oceans. Deglaciation occur ...

Glaciology Last Glacial Period