Cordilleran Ice Sheet glaciation of the Puget Lowland and Columbia Plateau and alpine glaciation of the North Cascade Range, Washington

2003 ◽  
pp. 137-157
Author(s):  
Don J. Easterbrook
Keyword(s):  
Ice Sheet ◽  
Cascade Range ◽  
Columbia Plateau ◽  
The North ◽  
Cordilleran Ice Sheet

Glacier Peak Tephra in the North Cascade Range, Washington: Stratigraphy, Distribution, and Relationship to Late-Glacial Events

1978 ◽  
Vol 10 (1) ◽  
pp. 30-41 ◽  
Author(s):  
Stephen C. Porter
Keyword(s):  
Far East ◽  
Ice Sheet ◽  
Late Glacial ◽  
Cascade Range ◽  
Time Layer ◽  
Terminal Moraine ◽  
The North ◽  
Stratigraphic Position ◽  
Cordilleran Ice Sheet ◽  
Glacial Time

Pumiceous tephra, resulting from multiple eruptions of Glacier Peak volcano in late-glacial time, mantles much of the landscape in the eastern North Cascade Range and extends eastward beyond the Columbia River as a thinner discontinuous deposit. Within about 25 km of the source, the tephra is divisible into as many as nine layers, distinguishable in the field on the basis of color, grain size, thickness, and stratigraphic position. Three principal layers, designated G (oldest), M, and B, are separated from one another by thinner, finer layers. Layer G has been found as far east as Montana and southern Alberta, whereas layer B has been identified as far as western Wyoming. By contrast, layer M trends nearly south, paralleling the crest of the Cascade Range. Available 14C dates indicate that the tephra complex was probably deposited between about 12,750 and 11,250 years ago. Glacier Peak tephra overlies moraines and associated outwash east of the Cascade Crest that were deposited about 14,000 years ago. Unreworked tephra occurs within several kilometers of many valley heads implying that major valley glaciers had nearly disappeared by the time of the initial tephra fall. Distribution of tephra indicates that the southern margin of the Cordilleran Ice Sheet had retreated at least 80 km north of its terminal moraine on the Waterville Plateau by the time layer G was deposited. Late-glacial moraines of the Rat Creek advance lie within the fallout area of layer M but lack the tephra on their surface implying that they were built subsequent to the eruption of this unit. Moraines of the Hyak advance at Snoqualmie Pass, which are correlated with the Rat Creek moraines farther north, were constructed prior to 11,000 14C years ago. The late-glacial advance along the Cascade Crest, therefore, apparently culminated between about 12,000 and 11,000 14C years ago and was broadly in phase with the Sumas readvance of the Cordilleran Ice Sheet in the Fraser Lowland which occurred between about 11,800 and 11,400 14C years ago.

Evidence of meltwater pulses into the North Pacific over the last 20 ka due to the decay of Kamchatka Glaciers and Cordilleran Ice Sheet

2019 ◽  
Vol 172 ◽  
pp. 33-44 ◽  
Author(s):  
Sergey Gorbarenko ◽  
Xuefa Shi ◽  
Jianjun Zou ◽  
Tatyana Velivetskaya ◽  
Antonina Artemova ◽  
...  
Keyword(s):  
North Pacific ◽  
Ice Sheet ◽  
The North ◽  
Cordilleran Ice Sheet ◽  
The North Pacific

scholarly journals Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene

2017 ◽  
Vol 43 (2) ◽  
pp. 467 ◽  
Author(s):  
J.L. Riedel
Keyword(s):  
British Columbia ◽  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Cascade Range ◽  
North Cascades ◽  
Alpine Glacier ◽  
The North ◽  
Alpine Glaciers ◽  
The Last Glacial Maximum ◽  
The Last Glacial

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 Cascades at 16 ka, glacial ELAs were 500-700 m lower than today, and during advances from 13.7 to 11.6 ka alpine glacier ELAs were 200-400 m lower.

Landform assemblages produced by the Laurentide Ice Sheet in northeastern British Columbia and adjacent Northwest Territories — constraints on glacial lakes and patterns of ice retreatThis article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.

2008 ◽  
Vol 45 (5) ◽  
pp. 593-610 ◽  
Author(s):  
Jan M. Bednarski
Keyword(s):  
British Columbia ◽  
Northwest Territories ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Ice Flow ◽  
The North ◽  
Relative Chronology ◽  
Mountain Front ◽  
Ice Retreat ◽  
Cordilleran Ice Sheet

The Laurentide Ice Sheet reached the Canadian Cordillera during the last glacial maximum in northeastern British Columbia and adjacent Northwest Territories and all regional drainage to unglaciated areas in the north was dammed by the ice. Converging ice-flow patterns near the mountain front suggest that the Laurentide Ice Sheet likely coalesced with the Cordilleran Ice Sheet during the last glaciation. With deglaciation, the ice masses separated, but earlier ice retreat in the south meant that meltwater pooled between the mountain front and the Laurentide margin. The level of the flooding was controlled by persistent ice cover on the southern Franklin Mountains. Glacial Lake Liard formed when the Laurentide Ice Sheet retreated east of the southern Liard Range and, at its maximum extent, may have impounded water at least as far south as the Fort Nelson River. Deglaciation of the plains was marked by local variations in ice flow caused by a thin ice sheet becoming more affected by the topography and forming lobes in places. These lobes caused diversions in local drainage readily traced by abandoned meltwater channels. Radiocarbon ages from adjacent areas suggest the relative chronology of deglaciation presented here occurred between 13 and 11 ka BP.

scholarly journals Mountain uplift and the glaciation of North America – a sensitivity study

2010 ◽  
Vol 6 (5) ◽  
pp. 707-717 ◽  
Author(s):  
G. L. Foster ◽  
D. J. Lunt ◽  
R. R. Parrish
Keyword(s):  
Northern Hemisphere ◽  
North American ◽  
Isotope Composition ◽  
Ice Sheet ◽  
Threshold Value ◽  
Sensitivity Study ◽  
North American Cordillera ◽  
North American Continent ◽  
The North ◽  
Cordilleran Ice Sheet

Abstract. The Miocene (~24 to ~5 million years ago) was a period of relative global warmth compared to the Quaternary (~2 million years ago to present; e.g. Zachos et al., 2001) and was characterised by the intermittent glaciation of Antarctica only. Paradoxically, the majority of available proxy data suggest that during the Miocene, pCO2 was similar, or even lower, than the pre-industrial levels (280 ppmv; Pagani et al., 1999; Pearson and Palmer, 2000; Kürschner et al., 1996, 2008) and at times probably crossed the modelled threshold value required for sustained glaciation in the Northern Hemisphere (DeConto et al., 2008). Records of ice rafted debris and the oxygen isotope composition of benthic foraminifera suggest that at several times over the last 25 million years substantial amounts of continental ice did build up in the Northern Hemisphere but none of these led to prolonged glaciation. In this contribution, we review evidence that suggests that in the Miocene the North American Cordillera was, at least in parts, considerably lower than today. We present new GCM simulations that imply that small amounts of uplift of the North American Cordillera result in significant cooling of the northern North American Continent. Offline ice sheet modelling, driven by these GCM outputs, suggests that with a reduced topography, inception of the Cordilleran ice sheet is prohibited. This suggests that uplift of the North American Cordillera in the Late Miocene may have played an important role in priming the climate for the intensification of Northern Hemisphere glaciation in the Late Pliocene.

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