Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene
Glacial retreat from the North Cascade Range after the Last Glacial Maximum (LGM) at approximately 21 ka until the end of the Pleistocene at 11.6 ka was complex and included both continental and alpine glaciers. Alpine valley glaciers reached their maximum extent before 21.4 ka, then underwent a pun...
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Universidad de La Rioja
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ftdoajarticles:oai:doaj.org/article:b706e0136bc24559be72e57603954195 2023-05-15T16:40:14+02:00 Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene J.L. Riedel 2017-09-01T00:00:00Z https://doi.org/10.18172/cig.3236 https://doaj.org/article/b706e0136bc24559be72e57603954195 EN ES eng spa Universidad de La Rioja https://publicaciones.unirioja.es/ojs/index.php/cig/article/view/3236 https://doaj.org/toc/0211-6820 https://doaj.org/toc/1697-9540 0211-6820 1697-9540 doi:10.18172/cig.3236 https://doaj.org/article/b706e0136bc24559be72e57603954195 Cuadernos de Investigación Geográfica, Vol 43, Iss 2, Pp 467-496 (2017) pleistocene deglaciation ice age north cascades Geography (General) G1-922 article 2017 ftdoajarticles https://doi.org/10.18172/cig.3236 2022-12-31T07:28:09Z Glacial retreat from the North Cascade Range after the Last Glacial Maximum (LGM) at approximately 21 ka until the end of the Pleistocene at 11.6 ka was complex and included both continental and alpine glaciers. Alpine valley glaciers reached their maximum extent before 21.4 ka, then underwent a punctuated retreat to valley heads. In the south, beyond the reach of ice sheet glaciation, several end moraines were deposited after the LGM. Moraines marking a re-advance of alpine glaciers to 5 km below modern glaciers were deposited from 13.7 to 11.6 ka. The Cordilleran Ice Sheet flowed south from near 52° north latitude in British Columbia into the North Cascades. At its maximum size the ice sheet covered more than 500 km2 and had a surface elevation of 2200 m in upper Skagit valley. Deglaciation commenced about 16 ka by frontal retreat of ice flanking the mountains. Surface lowering eventually exposed regional hydrologic divides and stranded ice masses more than 1000 m thick in valleys. Isolated fragments of the ice sheet disintegrated rapidly from 14.5 to 13.5 ka, with the pattern of deglaciation in each valley controlled by valley orientation, topography, and climate. Like alpine glaciers to the south, retreat of the ice sheet remnants was slowed by millennial scale climate fluctuations that produced at least one large recessional moraine, and multiple lateral moraines and kame terraces from elevations of 200-1400 m in most valleys. Large volumes of glacial meltwater flowed through the North Cascades and was concentrated in the Skagit and Methow rivers. Outburst floods from deep proglacial lakes spilled across divides and down steep canyons, depositing coarse gravel terraces and alluvial fans at valley junctions. Climate at the LGM was characterized by a mean summer temperature 6 to 7 ºC cooler than today, and 40% lower mean annual precipitation. Persistence of this climate for thousands of years before the LGM caused a 750-1000 m decrease in alpine glacier equilibrium line altitudes (ELA). In the southern North ... Article in Journal/Newspaper Ice Sheet Directory of Open Access Journals: DOAJ Articles Ela ENVELOPE(9.642,9.642,63.170,63.170) Cuadernos de Investigación Geográfica 43 2 467 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English Spanish |
topic |
pleistocene deglaciation ice age north cascades Geography (General) G1-922 |
spellingShingle |
pleistocene deglaciation ice age north cascades Geography (General) G1-922 J.L. Riedel Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene |
topic_facet |
pleistocene deglaciation ice age north cascades Geography (General) G1-922 |
description |
Glacial retreat from the North Cascade Range after the Last Glacial Maximum (LGM) at approximately 21 ka until the end of the Pleistocene at 11.6 ka was complex and included both continental and alpine glaciers. Alpine valley glaciers reached their maximum extent before 21.4 ka, then underwent a punctuated retreat to valley heads. In the south, beyond the reach of ice sheet glaciation, several end moraines were deposited after the LGM. Moraines marking a re-advance of alpine glaciers to 5 km below modern glaciers were deposited from 13.7 to 11.6 ka. The Cordilleran Ice Sheet flowed south from near 52° north latitude in British Columbia into the North Cascades. At its maximum size the ice sheet covered more than 500 km2 and had a surface elevation of 2200 m in upper Skagit valley. Deglaciation commenced about 16 ka by frontal retreat of ice flanking the mountains. Surface lowering eventually exposed regional hydrologic divides and stranded ice masses more than 1000 m thick in valleys. Isolated fragments of the ice sheet disintegrated rapidly from 14.5 to 13.5 ka, with the pattern of deglaciation in each valley controlled by valley orientation, topography, and climate. Like alpine glaciers to the south, retreat of the ice sheet remnants was slowed by millennial scale climate fluctuations that produced at least one large recessional moraine, and multiple lateral moraines and kame terraces from elevations of 200-1400 m in most valleys. Large volumes of glacial meltwater flowed through the North Cascades and was concentrated in the Skagit and Methow rivers. Outburst floods from deep proglacial lakes spilled across divides and down steep canyons, depositing coarse gravel terraces and alluvial fans at valley junctions. Climate at the LGM was characterized by a mean summer temperature 6 to 7 ºC cooler than today, and 40% lower mean annual precipitation. Persistence of this climate for thousands of years before the LGM caused a 750-1000 m decrease in alpine glacier equilibrium line altitudes (ELA). In the southern North ... |
format |
Article in Journal/Newspaper |
author |
J.L. Riedel |
author_facet |
J.L. Riedel |
author_sort |
J.L. Riedel |
title |
Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene |
title_short |
Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene |
title_full |
Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene |
title_fullStr |
Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene |
title_full_unstemmed |
Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene |
title_sort |
deglaciation of the north cascade range, washington and british columbia, from the last glacial maximum to the holocene |
publisher |
Universidad de La Rioja |
publishDate |
2017 |
url |
https://doi.org/10.18172/cig.3236 https://doaj.org/article/b706e0136bc24559be72e57603954195 |
long_lat |
ENVELOPE(9.642,9.642,63.170,63.170) |
geographic |
Ela |
geographic_facet |
Ela |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_source |
Cuadernos de Investigación Geográfica, Vol 43, Iss 2, Pp 467-496 (2017) |
op_relation |
https://publicaciones.unirioja.es/ojs/index.php/cig/article/view/3236 https://doaj.org/toc/0211-6820 https://doaj.org/toc/1697-9540 0211-6820 1697-9540 doi:10.18172/cig.3236 https://doaj.org/article/b706e0136bc24559be72e57603954195 |
op_doi |
https://doi.org/10.18172/cig.3236 |
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Cuadernos de Investigación Geográfica |
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43 |
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2 |
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467 |
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1766030607045885952 |