A laboratory study of particle ploughing and pore-pressure feedback: a velocity-weakening mechanism for soft glacier beds

dc.contributor.author Thomason, Jason
dc.contributor.author Iverson, Neal
dc.contributor.author Iverson, Neal
dc.contributor.department Geological and Atmospheric Sciences
dc.date 2018-02-18T09:29:51.000
dc.date.accessioned 2020-06-30T04:03:24Z
dc.date.available 2020-06-30T04:03:24Z
dc.date.copyright Tue Jan 01 00:00:00 UTC 2008
dc.date.issued 2008-01-01
dc.description.abstract <p>If basal-water discharge and pressure are sufficiently high, a soft-bedded glacier will slip over its bed by ploughing, the process in which particles that span the ice–bed interface are dragged across the bed surface. Results of laboratory experiments indicate that resistance to ploughing can decrease with increasing ploughing velocity (velocity weakening). During ploughing at various velocities (15–400 m a−1), till was compacted in front of idealized particles, causing pore pressures there that were orders of magnitude higher than the ambient value. This excess pore pressure locally weakened the till in shear, thereby decreasing ploughing resistance by a factor of 3.0–6.6 with a six-fold increase in ploughing velocity. Characteristic timescales of pore-pressure diffusion and compaction down-glacier from ploughing particles depend on till diffusivity, ploughing velocity and sizes of ploughing particles. These timescales accurately predict the ranges of these variables over which excess pore pressure and velocity weakening occurred. Existing ploughing models do not account for velocity weakening. A new ploughing model with no adjustable parameters predicts ploughing resistance to no worse than 38% but requires that excess pore pressures be measured. Velocity weakening by this mechanism may affect fast glacier flow, sediment transport by bed deformation and basal seismicity.</p>
dc.description.comments <p>This article is from <em>Journal of Glaciology </em>54 (2008): 169, doi:<a href="http://dx.doi.org/10.3189/002214308784409008" target="_blank">10.3189/002214308784409008</a>. Posted with permission.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/ge_at_pubs/145/
dc.identifier.articleid 1142
dc.identifier.contextkey 10069316
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath ge_at_pubs/145
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/38076
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/ge_at_pubs/145/2008_Iverson_LaboratoryStudy.pdf|||Fri Jan 14 20:21:19 UTC 2022
dc.source.uri 10.3189/002214308784409008
dc.subject.disciplines Glaciology
dc.subject.disciplines Sedimentology
dc.title A laboratory study of particle ploughing and pore-pressure feedback: a velocity-weakening mechanism for soft glacier beds
dc.type article
dc.type.genre article
dspace.entity.type Publication
relation.isAuthorOfPublication 8f9617fd-0ee4-4473-b7bb-ef722542e676
relation.isOrgUnitOfPublication 29272786-4c4a-4d63-98d6-e7b6d6730c45
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