Glacial Lake Victoria, a high-level Antarctic Lake inferred from lacustrine deposits in Victoria Valley

2002 ◽  
Vol 17 (7) ◽  
pp. 697-706 ◽  
Author(s):  
Brenda L. Hall ◽  
George H. Denton ◽  
Bret Overturf ◽  
Chris H. Hendy
Keyword(s):  
Lake Victoria ◽  
Glacial Lake ◽  
Antarctic Lake ◽  
Lacustrine Deposits ◽  
High Level

Stratigraphic evidence for multiple drainings of glacial Lake Missoula along the Clark Fork River, Montana, USA

2006 ◽  
Vol 66 (2) ◽  
pp. 311-322 ◽  
Author(s):  
Larry N. Smith
Keyword(s):  
High Volume ◽  
High Energy ◽  
Glacial Lake ◽  
Last Glacial ◽  
Lacustrine Deposits ◽  
Clark Fork River ◽  
Gravel Bars ◽  
Northwest Montana ◽  
Lake Drainage ◽  
The Last Glacial

AbstractGlacial Lake Missoula, a source of Channeled Scabland flood waters, inundated valleys of northwest Montana to altitudes of ∼ 1265 m and to depths of >600 m, as evidenced by shorelines and silty lacustrine deposits. This study describes previously unrecognized catastrophic lake-drainage deposits that lie stratigraphically beneath the glacial-lake silts. The unconsolidated gravelly flood alluvium contains imbricated boulder-sized clasts, cross-stratified gravel with slip-face heights of 2–> 35 m, and 70- to 100-m-high gravel bars which all indicate a high-energy, high-volume alluvial environment. Gravel bars and high scablands were formed by catastrophic draining of one or possibly more early, high lake stands (1200–1265 m). Most glacial-lake silt, such as the Ninemile section, was deposited stratigraphically above the earlier deposits, represents a lower lake stand(s) (1050–1150 m), and was not deposited in lake(s) responsible for the highest discharge events. The glaciolacustrine silt-covered benches are incised by relict networks of valleys formed during the drainage of the last glacial lake. Significant erosion associated with the last lake draining was confined to the inner Clark Fork River canyon.

scholarly journals High level of intergenera gene exchange shapes the evolution of haloarchaea in an isolated Antarctic lake

2013 ◽  
Vol 110 (42) ◽  
pp. 16939-16944 ◽  
Author(s):  
M. Z. DeMaere ◽  
T. J. Williams ◽  
M. A. Allen ◽  
M. V. Brown ◽  
J. A. E. Gibson ◽  
...  
Keyword(s):  
Gene Exchange ◽  
Antarctic Lake ◽  
High Level

Northern extent of Lake Agassiz in eastern Saskatchewan

1977 ◽  
Vol 14 (6) ◽  
pp. 1286-1291 ◽  
Author(s):  
F. F. Langford
Keyword(s):  
Late Pleistocene ◽  
Glacial Lake ◽  
Main Body ◽  
Lake Agassiz ◽  
Lacustrine Deposits ◽  
Hydroelectric Dam ◽  
Glacial Lake Agassiz ◽  
Lacustrine Clay

Surveys for a proposed hydroelectric dam, disclosed extensive deposits of late Pleistocene lacustrine clay in the valleys of the Churchill and Reindeer Rivers. The presence of montmorillonite in these clays and the topographic configuration suggest continuous connection to the main body of Glacial Lake Agassiz. The presence of till layers above the lacustrine deposits is explained by subaqueous slumping rather than read vance of the glacier, which retreated from this area between 10 000 and 9 000 years ago.

scholarly journals Impact Of Nile Perch (Lates Niloticus) Overfishing On Technical Efficiency Of Fishers In Lake Victoria Tanzania

2020 ◽  
Author(s):  
Eliaza Mkuna ◽  
Lloyd JS Baiyegunhi
Keyword(s):  
Technical Efficiency ◽  
Lake Victoria ◽  
Mesh Size ◽  
Nile Perch ◽  
Data Envelopment ◽  
Significant Difference ◽  
Landing Sites ◽  
High Level ◽  
The Impact ◽  
Significant Factors

Abstract Lake Victoria fishery activities are of crucial economic importance to the communities around East Africa as they support the majority of fishers specifically through Nile perch fishing. As a consequence, increasing fishing pressure had also led to overfishing. This study employed the Data Envelopment Analysis (DEA) and Propensity Score Matching (PSM) techniques to assess the impact of Nile perch overfishing on technical efficiency of fishers based on a survey of 268 fishers across 10 landing sites in Lake Victoria, Tanzania. Results from the DEA show that, overall Nile perch fishers have average technical efficiency of 30% which indicates a high level of inefficiency. Specifically, there is no statistically significant difference in the technical efficiencies for Nile perch fishers who are overfishing and those who are not overfishing due to fisher’s mobility across the Lake. In addition, mode of propulsion and being a member of fishery organization were found to be statistically significant factors influencing inefficiency of Nile perch fishers. Furthermore, results from the probit estimates of the PSM show that being a member of fishery organization, quantity of Nile perch harvested per trip, age of a fishing vessel (boat), the gillnet mesh size and cost of fishing inputs have statistically significant effect in influencing the probability of Nile perch overfishing. However, further result indicates that Nile perch overfishing do not have statistically significant impact on fisher’s technical efficiency. Therefore, this study recommends a need to monitor and formalize fisher’s mobility as one of the alternative for co-management of the Lake. Also, overfishing can be controlled without necessarily affecting technical efficiency of Nile perch fishers through training and access to proper fishing gears.

Upper Grand Coulee: New views of a channeled scabland megafloods enigma

2021 ◽  
pp. 245-300
Author(s):  
Richard B. Waitt* ◽  
Brian F. Atwater ◽  
Karin Lehnigk ◽  
Isaac J. Larsen ◽  
Bruce N. Bjornstad ◽  
...  
Keyword(s):  
High Water ◽  
Glacial Lake ◽  
Two Dimensional ◽  
Stratigraphic Sequence ◽  
Last Glacial ◽  
Field Evidence ◽  
New Findings ◽  
High Level ◽  
Flow Consistency ◽  
Grand Coulee

ABSTRACT New findings about old puzzles occasion rethinking of the Grand Coulee, greatest of the scabland channels. Those puzzles begin with antecedents of current upper Grand Coulee. By a recent interpretation, the upper coulee exploited the former high-level valley of a preflood trunk stream that had drained to the southwest beside and across Coulee anticline or monocline. In any case, a constriction and sharp bend in nearby Columbia valley steered Missoula floods this direction. Completion of upper Grand Coulee by megaflood erosion captured flood drainage that would otherwise have continued to enlarge Moses Coulee. Upstream in the Sanpoil valley, deposits and shorelines of last-glacial Lake Columbia varied with the lake’s Grand Coulee outlet while also recording scores of Missoula floods. The Sanpoil evidence implies that upper Grand Coulee had approached its present intake depth early the last glaciation at latest, or more simply during a prior glaciation. An upper part of the Sanpoil section provides varve counts between the last tens of Missoula floods in a stratigraphic sequence that may now be linked to flood rhythmites of southern Washington by a set-S tephra from Mount St. Helens. On the floor of upper Grand Coulee itself, recently found striated rock and lodgement till confirm the long-held view, which Bretz and Flint had shared, that cutting of upper Grand Coulee preceded its last-glacial occupation by the Okanogan ice lobe. A dozen or more late Missoula floods registered as sand and silt in the lee of Steamboat Rock. Some of this field evidence about upper Grand Coulee may conflict with results of recent two-dimensional simulations for a maximum Lake Missoula. In these simulations only a barrier high above the present coulee intake enables floods to approach high-water marks near Wenatchee that predate stable blockage of Columbia valley by the Okanogan lobe. Above the walls of upper Grand Coulee, scabland limits provide high-water targets for two-dimensional simulations of watery floods. The recent models sharpen focus on water sources, prior coulee incision, and coulee’s occupation by the Okanogan ice lobe. Field reappraisal continues downstream from Grand Coulee on Ephrata fan. There, some of the floods exiting lower Grand Coulee had bulked up with fine sediment from glacial Lake Columbia, upper coulee till, and a lower coulee lake that the fan itself impounded. Floods thus of debris-flow consistency carried outsize boulders previously thought transported by watery floods. Below Ephrata fan, a backflooded reach of Columbia valley received Grand Coulee outflow of small, late Missoula floods. These late floods can—by varve counts in post-S-ash deposits of Sanpoil valley—be clocked now as a decade or less apart. Still farther downstream, Columbia River gorge choked the largest Missoula floods, passing peak discharge only one-third to one-half that released by the breached Lake Missoula ice dam.

scholarly journals Diverse Biotransformation of Sulfur in Antarctic Lake Sediments

2021 ◽  
Author(s):  
Lili Shen ◽  
Tao Huang ◽  
Yuanqing Chen ◽  
Zhuding Chu ◽  
Zhouqing Xie
Keyword(s):  
Microbial Communities ◽  
Sulfate Reduction ◽  
Sulfur Oxidation ◽  
Freshwater Ecosystems ◽  
Organic Sulfur ◽  
Antarctic Lake ◽  
Fildes Peninsula ◽  
Degrading Bacteria ◽  
Sulfur Oxidizing ◽  
High Level

Abstract Microbial communities, sulfur isotope of sulfides (δ34SAVS and δ34SCRS) and sulfur and oxygen isotopes of sulfate (δ34SSO4 and δ18OSO4) in sediments were analyzed to study the biotransformation of sulfur in a penguin-affected lake Y2 and a pristine YO from Fildes Peninsula, Antarctic Peninsula. The microbial communities in Y2 were mainly associated with penguin activities, while those in YO were limited by nutrients. The much enriched δ34SSO4 recorded at depth of 30, 41 and 52 cm in Y2 indicates very strong sulfate reduction therein. The sulfur-degrading bacteria Pseudomonas in 0–23 cm of Y2 was 3.5 times as abundant as that of sulfur oxidizing bacteria (SOB), indicating remarkable remineralization of organic sulfur. While abundant SOB and 34S-depleted sulfate indicate considerable sulfur oxidation in 34–56 cm layer in Y2. In YO sediments, the highest abundance of Desulfotalea and the most enriched δ34SSO4 (35.2‰) and δ34SCRS (2.5‰) indicate strongest sulfate reduction in 28 cm layer. High abundance of Pseudomonas indicates active remineralization of organic sulfur in 3–5 cm layer in YO. While the medium δ34SSO4 and considerable abundance of SOB and SRB indicate concurrence of sulfur oxidation and sulfate reduction in other layers in YO. Our results show that high level of organic matter inputs from penguin populations support the diverse microbial community and biotransformation of sulfur in freshwater ecosystems in Antarctica.

scholarly journals Glacial Lake Wright, a high-level Antarctic lake during the LGM and early Holocene

2001 ◽  
Vol 13 (1) ◽  
pp. 53-60 ◽  
Author(s):  
B.L. Hall ◽  
G.H. Denton ◽  
B. Overturf
Keyword(s):  
Early Holocene ◽  
Mcmurdo Dry Valleys ◽  
Glacial Lake ◽  
Dry Valleys ◽  
Large Lakes ◽  
Radiocarbon Dates ◽  
Dry Conditions ◽  
High Level ◽  
High Lake Levels ◽  
The Last Glacial

We report evidence of a large proglacial lake (Glacial Lake Wright) that existed in Wright Valley in the McMurdo Dry Valleys region of Antarctica at the last glacial maximum (LGM) and in the early Holocene. At its highstands, Glacial Lake Wright would have stretched 50 km and covered c. 210 km2. Chronology for lake-level changes comes from 30 AMS radiocarbon dates of lacustrine algae preserved in deltas, shorelines, and glaciolacustrine deposits that extend up to 480 m above present-day lakes. Emerging evidence suggests that Glacial Lake Wright was only one of a series of large lakes to occupy the McMurdo Dry Valleys and the valleys fronting the Royal Society Range at the LGM. Although the cause of such high lake levels is not well understood, it is believed to relate to cool, dry conditions which produced fewer clouds, less snowfall, and greater amounts of absorbed radiation, leading to increased meltwater production.

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