Spatial variability in the flow of a valley glacier: Deformation of a large array of boreholes
Measurements of the deformation of a dense array of boreholes in Worthington Glacier, Alaska, show that the glacier moves with generally bed-parallel motion. Strain in the 200 m deep valley glacier is constant near the surface but follows a nonlinear vertical profile below a depth of about 120 m. By...
Published in: | Journal of Geophysical Research: Solid Earth |
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ScholarWorks at University of Montana
2001
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ftunivmontana:oai:scholarworks.umt.edu:geosci_pubs-1032 2024-09-09T19:41:11+00:00 Spatial variability in the flow of a valley glacier: Deformation of a large array of boreholes Harper, Joel T. Humphrey, Neil Pfeffer, W. Tad Huzurbazar, Snehalata V. Bahr, David B. Welch, Brian C. 2001-05-10T07:00:00Z application/pdf https://scholarworks.umt.edu/geosci_pubs/26 https://doi.org/10.1029/2000JB900440 https://scholarworks.umt.edu/context/geosci_pubs/article/1032/viewcontent/Harper_et_al_2001_Journal_of_Geophysical_Research__Solid_Earth__1978_2012_.pdf unknown ScholarWorks at University of Montana https://scholarworks.umt.edu/geosci_pubs/26 doi:10.1029/2000JB900440 https://scholarworks.umt.edu/context/geosci_pubs/article/1032/viewcontent/Harper_et_al_2001_Journal_of_Geophysical_Research__Solid_Earth__1978_2012_.pdf © 2001 by the Amiercan Geophysical Union Geosciences Faculty Publications Earth Sciences Geophysics and Seismology text 2001 ftunivmontana https://doi.org/10.1029/2000JB900440 2024-06-20T05:32:53Z Measurements of the deformation of a dense array of boreholes in Worthington Glacier, Alaska, show that the glacier moves with generally bed-parallel motion. Strain in the 200 m deep valley glacier is constant near the surface but follows a nonlinear vertical profile below a depth of about 120 m. By a depth of 180 m, the octahedral strain rate reaches 0.35 yr-1. The three-dimensional velocity field shows spatial complexity with significant deviations from plane strain, despite relatively simple valley geometry in the vicinity of the 6 x 106 m3 study volume. No evidence was found for time-varying deformation or movement along localized shear planes. Observations were made by repeatedly measuring the long-axis geometry of 31 closely spaced boreholes over a 70 day period, and three additional holes after 1 full year of deformation. The holes were spaced 15 to 30 m apart. Installation and measurement of such a large number of boreholes required the development of a semi-automated hot water drilling system that creates straight and vertical boreholes with uniform walls. The equipment and procedures enables borehole profiles to be measured without the use of hole casing. Inclinometry measurements collected in the holes were processed, analyzed for error, and visualized as a fully three-dimensional data set. the new methods offer unique insight into small-scale spatial and temporal variations in the pattern of flow in a valley glacier. Text glacier Alaska University of Montana: ScholarWorks Journal of Geophysical Research: Solid Earth 106 B5 8547 8562 |
institution |
Open Polar |
collection |
University of Montana: ScholarWorks |
op_collection_id |
ftunivmontana |
language |
unknown |
topic |
Earth Sciences Geophysics and Seismology |
spellingShingle |
Earth Sciences Geophysics and Seismology Harper, Joel T. Humphrey, Neil Pfeffer, W. Tad Huzurbazar, Snehalata V. Bahr, David B. Welch, Brian C. Spatial variability in the flow of a valley glacier: Deformation of a large array of boreholes |
topic_facet |
Earth Sciences Geophysics and Seismology |
description |
Measurements of the deformation of a dense array of boreholes in Worthington Glacier, Alaska, show that the glacier moves with generally bed-parallel motion. Strain in the 200 m deep valley glacier is constant near the surface but follows a nonlinear vertical profile below a depth of about 120 m. By a depth of 180 m, the octahedral strain rate reaches 0.35 yr-1. The three-dimensional velocity field shows spatial complexity with significant deviations from plane strain, despite relatively simple valley geometry in the vicinity of the 6 x 106 m3 study volume. No evidence was found for time-varying deformation or movement along localized shear planes. Observations were made by repeatedly measuring the long-axis geometry of 31 closely spaced boreholes over a 70 day period, and three additional holes after 1 full year of deformation. The holes were spaced 15 to 30 m apart. Installation and measurement of such a large number of boreholes required the development of a semi-automated hot water drilling system that creates straight and vertical boreholes with uniform walls. The equipment and procedures enables borehole profiles to be measured without the use of hole casing. Inclinometry measurements collected in the holes were processed, analyzed for error, and visualized as a fully three-dimensional data set. the new methods offer unique insight into small-scale spatial and temporal variations in the pattern of flow in a valley glacier. |
format |
Text |
author |
Harper, Joel T. Humphrey, Neil Pfeffer, W. Tad Huzurbazar, Snehalata V. Bahr, David B. Welch, Brian C. |
author_facet |
Harper, Joel T. Humphrey, Neil Pfeffer, W. Tad Huzurbazar, Snehalata V. Bahr, David B. Welch, Brian C. |
author_sort |
Harper, Joel T. |
title |
Spatial variability in the flow of a valley glacier: Deformation of a large array of boreholes |
title_short |
Spatial variability in the flow of a valley glacier: Deformation of a large array of boreholes |
title_full |
Spatial variability in the flow of a valley glacier: Deformation of a large array of boreholes |
title_fullStr |
Spatial variability in the flow of a valley glacier: Deformation of a large array of boreholes |
title_full_unstemmed |
Spatial variability in the flow of a valley glacier: Deformation of a large array of boreholes |
title_sort |
spatial variability in the flow of a valley glacier: deformation of a large array of boreholes |
publisher |
ScholarWorks at University of Montana |
publishDate |
2001 |
url |
https://scholarworks.umt.edu/geosci_pubs/26 https://doi.org/10.1029/2000JB900440 https://scholarworks.umt.edu/context/geosci_pubs/article/1032/viewcontent/Harper_et_al_2001_Journal_of_Geophysical_Research__Solid_Earth__1978_2012_.pdf |
genre |
glacier Alaska |
genre_facet |
glacier Alaska |
op_source |
Geosciences Faculty Publications |
op_relation |
https://scholarworks.umt.edu/geosci_pubs/26 doi:10.1029/2000JB900440 https://scholarworks.umt.edu/context/geosci_pubs/article/1032/viewcontent/Harper_et_al_2001_Journal_of_Geophysical_Research__Solid_Earth__1978_2012_.pdf |
op_rights |
© 2001 by the Amiercan Geophysical Union |
op_doi |
https://doi.org/10.1029/2000JB900440 |
container_title |
Journal of Geophysical Research: Solid Earth |
container_volume |
106 |
container_issue |
B5 |
container_start_page |
8547 |
op_container_end_page |
8562 |
_version_ |
1809910642486804480 |