![Schoolroom Glacier from Hurricane Pass](https://upload.wikimedia.org/wikipedia/commons/0/02/Schoolroom_Glacier_from_Hurricane_Pass.jpg)
In geology, a proglacial lake is a lake formed either by the damming action of a
moraine
A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice shee ...
during the retreat of a melting
glacier
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
, a glacial ice dam, or by meltwater trapped against an
ice sheet
In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at Las ...
due to
isostatic depression
Isostatic depression is the sinking of large parts of the Earth's crust into the asthenosphere caused by a heavy weight placed on the Earth's surface, often glacial ice during continental glaciation. Isostatic depression and isostatic rebound o ...
of the crust around the ice.
At the end of the
last ice age about 10,000 years ago, large proglacial lakes were a widespread feature in the northern hemisphere.
Moraine-dammed
![Glacial Tarn Formation EN](https://upload.wikimedia.org/wikipedia/commons/f/fe/Glacial_Tarn_Formation_EN.svg)
The receding glaciers of the tropical
Andes
The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
have formed a number of proglacial lakes, especially in the
Cordillera Blanca
The Cordillera Blanca (Spanish for "white range") is a mountain range in Peru that is part of the larger Andes range and extends for between 8°08' and 9°58'S and 77°00' and 77°52'W, in a northwesterly direction. It includes several peaks ove ...
of Peru, where 70% of all tropical glaciers are. Several such lakes have formed rapidly during the 20th century. These lakes may burst, creating a hazard for zones below. Many natural dams (usually
moraines
A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice she ...
) containing the lake water have been reinforced with safety dams. Some 34 such dams have been built in the
Cordillera Blanca
The Cordillera Blanca (Spanish for "white range") is a mountain range in Peru that is part of the larger Andes range and extends for between 8°08' and 9°58'S and 77°00' and 77°52'W, in a northwesterly direction. It includes several peaks ove ...
to contain proglacial lakes.
Several proglacial lakes have also formed in recent decades at the end of glaciers on the eastern side of
New Zealand's Southern Alps
The Southern Alps (; officially Southern Alps / Kā Tiritiri o te Moana) is a mountain range extending along much of the length of New Zealand's South Island, reaching its greatest elevations near the range's western side. The name "Souther ...
. The most accessible,
Lake Tasman, hosts boat trips for tourists.
On a smaller scale, a mountain glacier may excavate a depression forming a
cirque
A (; from the Latin word ') is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie (from Scottish Gaelic , meaning a pot or cauldron) and (; ). A cirque may also be a similarly shaped landform ...
, which may contain a mountain lake, called a
tarn, upon the melting of the glacial ice.
Ice-dammed
The
movement of a glacier may flow down a
valley
A valley is an elongated low area often running between Hill, hills or Mountain, mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers ...
to a confluence where the other branch carries an unfrozen river. The
glacier
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
blocks the river, which backs up into a proglacial lake, which eventually overflows or undermines the ice dam, suddenly releasing the impounded water in a
glacial lake outburst flood
A glacial lake outburst flood (GLOF) is a type of outburst flood caused by the failure of a dam containing a glacial lake. An event similar to a GLOF, where a body of water contained by a glacier melts or overflows the glacier, is called a jö ...
also known by its Icelandic name a
jökulhlaup
A jökulhlaup ( ) (literally "glacial run") is a type of glacial outburst flood. It is an Icelandic term that has been adopted in glaciological terminology in many languages.
It originally referred to the well-known subglacial outburst flood ...
. Some of the largest glacial floods in North American history were from
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, it ...
.
In modern times, the
Hubbard Glacier
__NOTOC__
Hubbard Glacier ( Lingít: ''Sít' Tlein'') is a glacier located in Wrangell–St. Elias National Park and Preserve in eastern Alaska and Kluane National Park and Reserve in Yukon, Canada, and named after Gardiner Hubbard.
Geography ...
regularly blocks the mouth of
Russell Fjord
Russell Fjord is a fjord in the U.S. state of Alaska. It extends north to Disenchantment Bay, the terminus of Hubbard Glacier, at the head of Yakutat Bay. The fjord was named in 1901 by Marcus Baker of the U.S. Geological Survey for explorer Isr ...
at 60° north on the coast of Alaska.
A similar event takes place after irregular periods in the
Perito Moreno Glacier
The Perito Moreno Glacier () is a glacier located in Los Glaciares National Park in southwest Santa Cruz Province, Argentina. It is one of the most important tourist attractions in the Argentine Patagonia.
The ice formation, in length, is one ...
, located in
Patagonia
Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and gl ...
. Roughly every four years the glacier forms an ice dam against the rocky coast, causing the waters of the
Lago Argentino
Lago Argentino is a lake in the Patagonian province of Santa Cruz, Argentina, at . It is the biggest freshwater lake in Argentina, with a surface area of (maximum width: ). It has an average depth of , and a maximum depth of .
The lake lies with ...
to rise. When the water pressure is too high, then the giant bridge collapses in what has become a major tourist attraction. This sequence occurred last on 4 March 2012, the previous having taken place four years before, in July 2008.
About 13,000 years ago in North America, the
Cordilleran Ice Sheet crept southward into the
Idaho Panhandle
The Idaho Panhandle—locally known as North Idaho—is a salient region of the U.S. state of Idaho encompassing the state's 10 northernmost counties: Benewah, Bonner, Boundary, Clearwater, Idaho, Kootenai, Latah, Lewis, Nez Perce, and Shosh ...
, forming a large ice dam that blocked the mouth of the
Clark Fork River, creating a massive lake deep and containing more than of water. Finally this
Glacial Lake Missoula
Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. The lake measured about and contained about of water, half the volume of Lake Mic ...
burst through the ice dam and exploded downstream, flowing at a rate 10 times the combined flow of all the rivers of the world. Because such ice dams can re-form, these
Missoula Floods
The Missoula floods (also known as the Spokane floods or the Bretz floods or Bretz's floods) were cataclysmic glacial lake outburst floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ...
happened at least 59 times, carving
Dry Falls
Dry Falls is a scalloped precipice with four major alcoves, in central Washington scablands. This cataract complex is on the opposite side of the Upper Grand Coulee from the Columbia River, and at the head of the Lower Grand Coulee, northern ...
below
Grand Coulee
Grand Coulee is an ancient river bed in the U.S. state of Washington. This National Natural Landmark stretches for about 60 miles (100 km) southwest from Grand Coulee Dam to Soap Lake, being bisected by Dry Falls into the Upper and Lower ...
.
In some cases, such lakes gradually evaporated during the warming period after the
Quaternary
The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...
ice age. In other cases, such as
Glacial Lake Missoula
Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. The lake measured about and contained about of water, half the volume of Lake Mic ...
and
Glacial Lake Wisconsin
Glacial Lake Wisconsin was a prehistoric proglacial lake that existed from approximately 18,000 to 14,000 years ago, at the end of the last ice age, in the central part of present-day Wisconsin in the United States.
Formation and demise
Before t ...
in the United States, the sudden rupturing of the supporting dam caused
glacial lake outburst flood
A glacial lake outburst flood (GLOF) is a type of outburst flood caused by the failure of a dam containing a glacial lake. An event similar to a GLOF, where a body of water contained by a glacier melts or overflows the glacier, is called a jö ...
s, the rapid and catastrophic release of dammed water resulting in the formation of gorges and other structures downstream from the former lake. Good examples of these structures can be found in the
Channeled Scablands
The Channeled Scablands are a relatively barren and soil-free region of interconnected relict and dry flood channels, coulees and cataracts eroded into Palouse loess and the typically flat-lying basalt flows that remain after cataclysmic floods ...
of eastern Washington, an area heavily eroded by the
Missoula Floods
The Missoula floods (also known as the Spokane floods or the Bretz floods or Bretz's floods) were cataclysmic glacial lake outburst floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ...
.
[http://www.cr.nps.gov/history/online_books/geology/publications/inf/72-2/sec5.htm USGS The Channeled Scablands of Eastern Washington]
The following table is a partial list of rivers that had glacial ice dams.
Retreating ice sheet
The retreating glaciers of the last ice age, both depressed the terrain with their mass and provided a source of meltwater that was confined against the ice mass.
Lake Algonquin
Lake Algonquin was a prehistoric proglacial lake that existed in east-central North America at the time of the last ice age. Parts of the former lake are now Lake Huron, Georgian Bay, Lake Superior, Lake Michigan, Lake Nipigon, and Lake Nipissing ...
is an example of a proglacial lake that existed in east-central North America at the time of the last
ice age
An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...
. Parts of the former lake are now
Lake Huron
Lake Huron ( ) is one of the five Great Lakes of North America. Hydrology, Hydrologically, it comprises the easterly portion of Lake Michigan–Huron, having the same surface elevation as Lake Michigan, to which it is connected by the , Strait ...
,
Georgian Bay
Georgian Bay (french: Baie Georgienne) is a large bay of Lake Huron, in the Laurentia bioregion. It is located entirely within the borders of Ontario, Canada. The main body of the bay lies east of the Bruce Peninsula and Manitoulin Island. To ...
,
Lake Superior
Lake Superior in central North America is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. and the third-largest by volume, holding 10% of the world's surface fresh wa ...
,
Lake Michigan
Lake Michigan is one of the five Great Lakes of North America. It is the second-largest of the Great Lakes by volume () and the third-largest by surface area (), after Lake Superior and Lake Huron. To the east, its basin is conjoined with that o ...
and inland portions of northern Michigan.
[ Examples in Great Britain include ]Lake Lapworth Lake Lapworth was a postulated glacial lake in Great Britain, believed to have formed during the last ice age when glaciers ended the northern outlet of the Severn. This ran through the Dee (which passes by Chester). At some point or points it ran ...
, Lake Harrison
Lake Harrison or Lake Bosworth is the name given to a lake that in parts of the Ice Age may have covered much of the Midlands in England around Warwick, Birmingham and Leicester. It is suggested that it was formed when ice sheets over Wales and N ...
and Lake Pickering
Lake Pickering was an extensive proglacial lake of the Devensian glacial. It filled the Vale of Pickering between the North York Moors and the Yorkshire Wolds, when the (largely Scandinavian) ice blocked the drainage, which had flowed north-east ...
. Ironbridge Gorge in Shropshire and Hubbard's Hills
Hubbard's Hills is an area of natural beauty directly to the west of Louth, Lincolnshire, Louth, Lincolnshire, England and is popular for family picnics, school field trips and dog walking. The park is dedicated to the memory of Annie Pahud.
Topo ...
in Lincolnshire are examples of a glacial overspill channel created when the water of a proglacial lake rose high enough to breach the lowest point in the containing watershed.
See also
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*
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*
*Lacustrine Plain A lacustrine plain or lake plain is a plain formed due to the past existence of a lake and its accompanying sediment accumulation. Lacustrine plains can be formed through one of three major mechanisms: glacial drainage, differential uplift, and inla ...
References
Bibliography
*Baker, V.R., Benito, G., and Rudoy, A.N., 1993. Paleo-hydrology of late Pleistocene superflooding, Altay Mountains, Siberia: Science, 259, p. 348–350.
*Lord, M.L., and Kehew, A.E., 1987, Sedimentology and paleohydrology of glacial-lake outburst deposits in southeastern Saskatchewan and northwestern North Dakota: Geological Society of America Bulletin v. 99, p. 663–673.
*Matsch, C.L., 1983, River Warren, the southern outlet of Glacial Lake Agassiz, in Teller, J.T., and Lee, Clayton, Glacial Lake Agassiz: Geological Association of Canada Special Paper 26, p. 231–244.
*Mayo, L.R., 1989, Advance of Hubbard Glacier and 1986 outburst of Russell Fiord, Alaska, U.S.A.: Annals of Glaciology, v. 13, p. 189–194.
*O'Connor, J.E., and Baker, V.R., 1992, Magnitudes and implications of peak discharges from Glacial Lake Missoula: Geological Society of America Bulletin, v. 104, p. 267–279.
*Rudoy, A., 1998, Mountain ice-dammed lakes of southern Siberia and their influence on the development and regime of the intracontinental runoff systems of North Asia in the late Pleistocene, in Benito, G., Baker, V.R., and Gregory, K.J., eds., Paleohydrology and Environmental Change: John Wiley and Sons, p. 215–234.
*Thorson, R.M., 1989, Late Quaternary paleofloods along the Porcupine River, Alaska—Implication for regional correlation, in Carter, L.D., Hamilton, T.D., and Galloway, J.P., eds., Late Cenozoic history of the interior basins of Alaska and the Yukon: U.S. Geological Survey Circular 1026, p. 51–54.
*Vaughn, D., and Ash, D.W., 1983, Paleohydrology and geomorphology of selected reaches of the upper Wabash River, Indiana: Geological Society of America Program with Abstracts, v. 15, no. 6, p. 711.
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Lacustrine landforms
Glacial lakes