scholarly journals Evidence from Keewatin (Central Nunavut) for Paleo-Ice Divide Migration*

2006 ◽  
Vol 58 (2-3) ◽  
pp. 163-186 ◽  
Author(s):  
Isabelle McMartin ◽  
Penny J. Henderson
Keyword(s):  
Flow Velocity ◽  
Mineral Exploration ◽  
Low Velocity ◽  
Ice Flow ◽  
Photo Interpretation ◽  
Field Mapping ◽  
Extensive Field ◽  
Basal Sliding ◽  
Ice Flows ◽  
Air Photo

Abstract Ice directional indicators were compiled from extensive field mapping and air-photo interpretation in the Keewatin region of central Nunavut. The profusion of multi-faceted bedrock outcrops, intersecting striations, superimposed streamlined landforms, and stacked till units, particularly beneath the former Keewatin Ice Divide, is interpreted to be the result of the migration of the main ice divide in the region, by as much as 500 km between ice-flow phases, possibly through much of the Wisconsinan glaciation. This palimpsest glacial landscape reflects protection under an ice divide because of low-velocity basal sliding, and changes in flow velocity as a result of shifting ice flow centres. Relative ages of regional ice-flow sets were used to reconstruct multiple phases of paleo-ice flows, stemming from ice centres external to the region prior to or at LGM, and from a local ice divide throughout deglaciation. This work refutes previous interpretations of the age and stability of the Keewatin Ice Divide, and has implications for interpreting glacial dispersal trains and for mineral exploration in Keewatin.

A Huronian outlier in the Goulais River area, District of Algoma, Ontario

1978 ◽  
Vol 15 (9) ◽  
pp. 1535-1537 ◽  
Author(s):  
E. C. Grunsky ◽  
J. T. Arengi
Keyword(s):  
Sedimentary Rock ◽  
Sedimentary Rocks ◽  
Photo Interpretation ◽  
Field Mapping ◽  
Nearby Source ◽  
Air Photo ◽  
Stratigraphic Thickness

An outlier of sedimentary rock assigned to the Gowganda Formation of the Huronian Supergroup was discovered during field mapping in the Goulais River area, District of Algoma, Ontario. This outlier is the northernmost documented occurrence of Huronian sedimentary rocks in the Algoma region. The outlier is 53 m in stratigraphic thickness and consists of polymictic to oligomictic paraconglomerate and orthoconglomerate with interbeds of pink arkose, siltstone, and dark grey greywacke. The conglomerates contain metavolcanic fragments and altered feldspars that suggest part of the sediment had a nearby source. Hematite results in a pink matrix in both conglomerates and arkosic interbeds and may indicate that an oxidizing environment prevailed during deposition. Air photo interpretation may help locate other outliers in the vicinity of lineaments, faults, or topographic highs.

scholarly journals Streaming flow of an Antarctic Peninsula palaeo-ice stream, both by basal sliding and deformation of substrate

2011 ◽  
Vol 57 (204) ◽  
pp. 596-608 ◽  
Author(s):  
Benedict T.I. Reinardy ◽  
Robert D. Larter ◽  
Claus-Dieter Hillenbrand ◽  
Tavi Murray ◽  
John F. Hiemstra ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Antarctic Peninsula ◽  
Outer Shelf ◽  
Inner Shelf ◽  
Ice Flow ◽  
Transparent Layer ◽  
Basal Sliding ◽  
Fast Ice ◽  
Fast Flow ◽  
Streaming Flow

AbstractAcoustic sub-bottom profiler surveys on the northeast Antarctic Peninsula shelf indicate that parts of the seabed are underlain by an acoustically transparent layer that is thin on the inner shelf and becomes thicker and more extensive towards the outer shelf. Sedimentological and geophysical data are combined to construct a bed model where streaming ice flow, by both deformation and basal sliding, took place within cross-shelf troughs. The model suggests only limited deformation contributed to fast flow on the inner shelf, i.e. in the onset zone of ice streaming, where the bed was predominantly underlain by a stiff till. Thus, fast ice flow in this area might have been by basal sliding, with deformation confined to discontinuous patches of soft till <40 cm thick. Towards the middle and outer shelf, extensive, thick sequences of soft till suggest a change in the dominant subglacial process towards widespread deformation. This downstream change from basal sliding to subglacial deformation is manifest in the transition from stiff-till dominance to soft-till dominance, while a downstream increase in ice flow velocity is evident from the complex geomorphic imprint on the inner shelf evolving to the more restricted set of bedforms on the outer shelf.

scholarly journals Short-term variations in flow velocity of Glaciar Soler, Patagonia, Chile

1992 ◽  
Vol 38 (128) ◽  
pp. 152-156 ◽  
Author(s):  
Renji Naruse ◽  
Hiroshi Fukami ◽  
Masamu Aniya
Keyword(s):  
Flow Velocity ◽  
Water Pressure ◽  
Water Discharge ◽  
Time Lag ◽  
Maximum Flow ◽  
Sliding Velocity ◽  
Short Term ◽  
Ice Flow ◽  
Glacier Terminus ◽  
Basal Sliding

AbstractShort-term variations in ice-flow velocity were obtained at intervals of a few hours and a few days in the ablation area of Glaciar Soler, Patagonia, Chile, in November 1985. A maximum flow rate was measured at about four times the minimum value. A good correlation, with a time lag of 7.5 h, was found between the ice-flow velocity in the lower reaches and the amount of water discharge from the glacier terminus. It was concluded, therefore, that the velocity variations should have resulted from the variations in basal sliding velocity which is strongly controlled by the subglacial water pressure.

scholarly journals Short-term variations in flow velocity of Glaciar Soler, Patagonia, Chile

1992 ◽  
Vol 38 (128) ◽  
pp. 152-156 ◽  
Author(s):  
Renji Naruse ◽  
Hiroshi Fukami ◽  
Masamu Aniya
Keyword(s):  
Flow Velocity ◽  
Water Pressure ◽  
Water Discharge ◽  
Time Lag ◽  
Maximum Flow ◽  
Sliding Velocity ◽  
Short Term ◽  
Ice Flow ◽  
Glacier Terminus ◽  
Basal Sliding

AbstractShort-term variations in ice-flow velocity were obtained at intervals of a few hours and a few days in the ablation area of Glaciar Soler, Patagonia, Chile, in November 1985. A maximum flow rate was measured at about four times the minimum value. A good correlation, with a time lag of 7.5 h, was found between the ice-flow velocity in the lower reaches and the amount of water discharge from the glacier terminus. It was concluded, therefore, that the velocity variations should have resulted from the variations in basal sliding velocity which is strongly controlled by the subglacial water pressure.

scholarly journals An Unconventional Field Mapping Application: A Complete Opensource Workflow Solution Applied to Lithological Mapping of the Coatings of Cultural Heritage

2021 ◽  
Vol 10 (6) ◽  
pp. 357
Author(s):  
Niccolò Iandelli ◽  
Massimo Coli ◽  
Tessa Donigaglia ◽  
Anna Livia Ciuffreda
Keyword(s):  
Cultural Heritage ◽  
Coating Materials ◽  
Historical Building ◽  
New Approach ◽  
Photo Interpretation ◽  
Organization Management ◽  
Field Mapping ◽  
Lithological Mapping ◽  
Entire Amount

The conservation of a primary importance historical building requires organization, management, continuous updating, comparison, and visualization of a large amount of data of different nature and origin. In relation to these aspects the use of a GIS brings various advantages including single and univocal management of the entire amount of existing data in a relational, dynamic, updatable and queryable way. The integration of a mobile solution permits the updating of the dataset and checking on site all information. The workflow presented uses opensource solutions, desktop and mobile, which allows the creation of an unconventional lithological Field Mapping activity: starting from photo interpretation and in situ survey, all the coating materials (stone, etc.) of some monuments of primary historical and cultural interest have been mapped (i.e., Duomo di Firenze, Duomo di Prato). The product can be considered as a lithological cartography, vertically oriented, processed by field surveys, geognostic surveys and photo interpretation. All combined to create a “lithological” mapping of the coatings of the various monuments; the advantage is a new approach for conservation and restoration of Cultural Heritage. The proposed workflow involves a mobile solution, opensource, that allows the verification and management of the database in the field.

scholarly journals Ice flow velocities over Vostok Subglacial Lake, East Antarctica, determined by 10 years of GNSS observations

2013 ◽  
Vol 59 (214) ◽  
pp. 315-326 ◽  
Author(s):  
A. Richter ◽  
D.V. Fedorov ◽  
M. Fritsche ◽  
S.V. Popov ◽  
V.Ya. Lipenkov ◽  
...  
Keyword(s):  
Flow Velocity ◽  
East Antarctica ◽  
Global Navigation Satellite Systems ◽  
Steady Increase ◽  
Lake Area ◽  
Ice Flow ◽  
Satellite Systems ◽  
Subglacial Lake ◽  
Gnss Observations ◽  
Flow Velocities

AbstractRepeated Global Navigation Satellite Systems (GNSS) observations were carried out at 50 surface markers in the Vostok Subglacial Lake (East Antarctica) region between 2001 and 2011. The horizontal ice flow velocity vectors were derived with accuracies of 1 cm a−1 and 0.5°, representing the first reliable information on ice flow kinematics in the northern part of the lake. Within the lake area, ice flow velocities do not exceed 2 m a−1. The ice flow azimuth is southeast in the southern part of the lake and turns gradually to east-northeast in the northern part. In the northern part, as the ice flow enters the lake at the western shore, the velocity decreases towards the central lake axis, then increases slightly past the central axis. In the southern part, a continued acceleration is observed from the central lake axis across the downstream grounding line. Based on the observed flow velocity vectors and ice thickness data, mean surface accumulation rates are inferred for four surface segments between Ridge B and Vostok Subglacial Lake and show a steady increase towards the north.

Evidence for a large surface ablation zone in central East Antarctica during the last Ice Age

2003 ◽  
Vol 59 (1) ◽  
pp. 114-121 ◽  
Author(s):  
Martin J. Siegert ◽  
Richard C. A. Hindmarsh ◽  
Gordon S. Hamilton
Keyword(s):  
Ice Core ◽  
Remote Sensing Data ◽  
Ice Age ◽  
Internal Layers ◽  
Ice Flow ◽  
Glacial Ice ◽  
Ice Surface ◽  
Ice Flows ◽  
Last Ice Age ◽  
The Hill

AbstractInternal isochronous ice sheet layers, recorded by airborne ice-penetrating radar, were measured along an ice flowline across a large (>1 km high) subglacial hill in the foreground of the Transantarctic Mountains. The layers, dated through an existing stratigraphic link with the Vostok ice core, converge with the ice surface as ice flows over the hill without noticeable change to their separation with each other or the ice base. A two-dimensional ice flow model that calculates isochrons and particle flowpaths and accounts for ice flow over the hill under steady-state conditions requires net ablation (via sublimation) over the stoss face for the predicted isochrons to match the measured internal layers. Satellite remote sensing data show no sign of exposed ancient ice at this site, however. Given the lack of exposed glacial ice, surface balance conditions must have changed recently from the net ablation that is predicted at this site for the last 85,000 years to accumulation.

scholarly journals Variations in the Sliding of a Temperate Glacier

1974 ◽  
Vol 13 (69) ◽  
pp. 349-369 ◽  
Author(s):  
Steven M. Hodge
Keyword(s):  
Water Discharge ◽  
Ice Flow ◽  
Sliding Speed ◽  
Temporary Storage ◽  
State Of Stress ◽  
Basal Sliding ◽  
Internal Deformation ◽  
Pressure Melting ◽  
Glacier Flow ◽  
Basal Shear

Detailed measurements of the positions of stakes along the center-line of the lower Nisqually Glacier were made over a period of two years. Variations in the basal sliding speed were calculated from the measured changes in surface speed, surface slope, and thickness, using the glacier flow model of Nye (1952) and allowing for the effect of the valley walls, longitudinal stress gradients, and uncertainties in the flow law of ice. The flow is predominantly by basal sliding and has a pronounced seasonal variation of approximately ±25%. Internal deformation contributes progressively less to the total motion with distance up-glacier. Neither the phase nor the magnitude of the seasonal velocity fluctuations can be accounted for by seasonal variations in the state of stress within the ice or at the bed, and the variations do not correlate directly with the melt-water discharge from the terminus. A seasonal wave in the ice flow travels down the glacier at a speed too high for propagation by internal deformation or the pressure melting/enhanced creep mechanism of basal sliding.The rate of sliding appears to be determined primarily by the amount of water in temporary storage in the glacier. The peak in sliding speed occurs, on the average, at the same time as the maximum liquid water storage of the South Cascade Glacier. The data support the idea that glaciers store water in the fall, winter and spring and then release it in the summer. This temporary storage may be greatest near the equilibrium line. The amount of stored water may increase over a period of years and be released catastrophically as a jökulhlaup. Any dependence of sliding on the basal shear stress is probably masked by the effect of variations in the hydrostatic pressure of water having access to the bed.

Friction at the bed does not control fast glacier flow

Science ◽  
2018 ◽  
Vol 361 (6399) ◽  
pp. 273-277 ◽  
Author(s):  
L. A. Stearns ◽  
C. J. van der Veen
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Strong Relationship ◽  
Frictional Stress ◽  
Ice Flow ◽  
Mountain Glaciers ◽  
Theoretical Predictions ◽  
Basal Sliding ◽  
Net Pressure ◽  
Glacier Flow

The largest uncertainty in the ice sheet models used to predict future sea level rise originates from our limited understanding of processes at the ice/bed interface. Near glacier termini, where basal sliding controls ice flow, most predictive ice sheet models use a parameterization of sliding that has been theoretically derived for glacier flow over a hard bed. We find that this sliding relation does not apply to the 140 Greenland glaciers that we analyzed. There is no relationship between basal sliding and frictional stress at the glacier bed, contrary to theoretical predictions. There is a strong relationship between sliding speed and net pressure at the glacier bed. This latter finding is in agreement with earlier observations of mountain glaciers that have been largely overlooked by the glaciological community.

scholarly journals Glacier disequilibrium in the Convoy Range, Transantarctic Mountains, Antarctica

1994 ◽  
Vol 20 ◽  
pp. 269-276 ◽  
Author(s):  
T.J. Chinn
Keyword(s):  
Field Work ◽  
Snow Accumulation ◽  
Low Velocity ◽  
Ice Flow ◽  
Outlet Glacier ◽  
Regime Changes ◽  
Positive Balance ◽  
Geological Map ◽  
Glacier Flow ◽  
Surficial Deposits

Field work for a geological map of the Convoy Range included mapping glaciers, moraines and surficial deposits. A range of glaciological indicators, including supraglacial and other moraines and margin morphology, has been used to assess the present equilibrium of the glaciers. Fields of rafted supraglacial moraine have accumulated over long periods of time at specific low-gradient, low-velocity locations. As the glacier regime changes, the shape of the moraine field distorts, signalling a change in flow pattern. By reversing the ice flow vectors directed at the moraine field, the directions from whence the debris came are shown. Unsorting the contortions of supraglacial moraine fields reveals the nature of the changes in glacier regime. Moraine-field configurations all suggest that local glaciers are expanding in response to higher local precipitation, estimated to have occurred between 2000 and 8000 year BP, most likely coincident with the world-wide “climatic optimum” of about 6000 year BP.Ice-cliff morphology, fresh terminal moraines and boulder trains indicate that larger local glaciers are currently receding from a Holocene maximum, while the margin of the large Mackay Ice Sheet outlet glacier shows no evidence of recent recession and is probably close to its Holocene maximum. In contrast, areas of present snow cover are expanding, superimposing a recent positive balance (decades to hundreds of years), which has yet to reverse a general recession of mid- to high-altitude glaciers. Local hollows in some névé areas imply that glacier flow is not in equilibrium with snow accumulation.

Sign in / Sign up

Export Citation Format

Share Document