Shear resistance and continuity of subglacial till: hydrology rules
The field observations of G.S. Boulton stimulated widespread interest in deformable beds. Shear resistance of till in its critical state is insensitive to strain rate and increases linearly with effective pressure. During unsteady deformation, pseudo-viscous shear resistance can be caused by dilatio...
Main Author: | |
---|---|
Format: | Text |
Language: | English |
Published: |
Iowa State University Digital Repository
2010
|
Subjects: | |
Online Access: | https://lib.dr.iastate.edu/ge_at_pubs/122 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1121&context=ge_at_pubs |
id |
ftiowastateuniv:oai:lib.dr.iastate.edu:ge_at_pubs-1121 |
---|---|
record_format |
openpolar |
spelling |
ftiowastateuniv:oai:lib.dr.iastate.edu:ge_at_pubs-1121 2023-05-15T13:36:09+02:00 Shear resistance and continuity of subglacial till: hydrology rules Iverson, Neal R. 2010-12-01T08:00:00Z application/pdf https://lib.dr.iastate.edu/ge_at_pubs/122 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1121&context=ge_at_pubs en eng Iowa State University Digital Repository https://lib.dr.iastate.edu/ge_at_pubs/122 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1121&context=ge_at_pubs Geological and Atmospheric Sciences Publications Glaciology Hydrology text 2010 ftiowastateuniv 2021-08-28T22:46:24Z The field observations of G.S. Boulton stimulated widespread interest in deformable beds. Shear resistance of till in its critical state is insensitive to strain rate and increases linearly with effective pressure. During unsteady deformation, pseudo-viscous shear resistance can be caused by dilation of consolidated tills and resultant pore-pressure decline. This effect is probably uncommon, however, because susceptible tills of low hydraulic diffusivity are also those least likely to consolidate significantly during effective-pressure transients. Stick–slip motion at Whillans Ice Stream, Antarctica, indicates that its basal till must weaken during rapid slip and strengthen during longer periods of slower slip. Recurrence intervals for rapid-slip episodes there (6–18 hours) indicate that till-strength variations, if driven by changes in pore pressure either related or unrelated to basal freezing, are focused in the uppermost several centimeters of the bed. Ploughing of grains at the bed surface and associated excess pore pressures in adjacent till can account for rate-weakening during rapid slip, with pore-pressure decay causing strengthening between slip episodes. By promoting shallow, sluggish subglacial water flow and low effective pressure, soft beds may help sustain themselves by slowing their own transport. Soft-bed shear resistance, kinematics and continuity are problems rooted in subglacial hydrology. Text Antarc* Antarctica Whillans Ice Stream Digital Repository @ Iowa State University Whillans ENVELOPE(-64.250,-64.250,-84.450,-84.450) Whillans Ice Stream ENVELOPE(-145.000,-145.000,-83.667,-83.667) |
institution |
Open Polar |
collection |
Digital Repository @ Iowa State University |
op_collection_id |
ftiowastateuniv |
language |
English |
topic |
Glaciology Hydrology |
spellingShingle |
Glaciology Hydrology Iverson, Neal R. Shear resistance and continuity of subglacial till: hydrology rules |
topic_facet |
Glaciology Hydrology |
description |
The field observations of G.S. Boulton stimulated widespread interest in deformable beds. Shear resistance of till in its critical state is insensitive to strain rate and increases linearly with effective pressure. During unsteady deformation, pseudo-viscous shear resistance can be caused by dilation of consolidated tills and resultant pore-pressure decline. This effect is probably uncommon, however, because susceptible tills of low hydraulic diffusivity are also those least likely to consolidate significantly during effective-pressure transients. Stick–slip motion at Whillans Ice Stream, Antarctica, indicates that its basal till must weaken during rapid slip and strengthen during longer periods of slower slip. Recurrence intervals for rapid-slip episodes there (6–18 hours) indicate that till-strength variations, if driven by changes in pore pressure either related or unrelated to basal freezing, are focused in the uppermost several centimeters of the bed. Ploughing of grains at the bed surface and associated excess pore pressures in adjacent till can account for rate-weakening during rapid slip, with pore-pressure decay causing strengthening between slip episodes. By promoting shallow, sluggish subglacial water flow and low effective pressure, soft beds may help sustain themselves by slowing their own transport. Soft-bed shear resistance, kinematics and continuity are problems rooted in subglacial hydrology. |
format |
Text |
author |
Iverson, Neal R. |
author_facet |
Iverson, Neal R. |
author_sort |
Iverson, Neal R. |
title |
Shear resistance and continuity of subglacial till: hydrology rules |
title_short |
Shear resistance and continuity of subglacial till: hydrology rules |
title_full |
Shear resistance and continuity of subglacial till: hydrology rules |
title_fullStr |
Shear resistance and continuity of subglacial till: hydrology rules |
title_full_unstemmed |
Shear resistance and continuity of subglacial till: hydrology rules |
title_sort |
shear resistance and continuity of subglacial till: hydrology rules |
publisher |
Iowa State University Digital Repository |
publishDate |
2010 |
url |
https://lib.dr.iastate.edu/ge_at_pubs/122 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1121&context=ge_at_pubs |
long_lat |
ENVELOPE(-64.250,-64.250,-84.450,-84.450) ENVELOPE(-145.000,-145.000,-83.667,-83.667) |
geographic |
Whillans Whillans Ice Stream |
geographic_facet |
Whillans Whillans Ice Stream |
genre |
Antarc* Antarctica Whillans Ice Stream |
genre_facet |
Antarc* Antarctica Whillans Ice Stream |
op_source |
Geological and Atmospheric Sciences Publications |
op_relation |
https://lib.dr.iastate.edu/ge_at_pubs/122 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1121&context=ge_at_pubs |
_version_ |
1766074938991575040 |