Internal structure of a Himalayan debris-covered glacier revealed by borehole optical televiewing
Characterising the structures within glaciers can give unique insight into ice motion processes. On debris-covered glaciers, traditional structural glaciological mapping is challenging because the lower glacier is hidden by the supraglacial debris layer. Here, we use high-resolution optical teleview...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Cambridge University Press
2023-08-01
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| Series: | Journal of Glaciology |
| Subjects: | |
| Online Access: | https://www.cambridge.org/core/product/identifier/S0022143022001009/type/journal_article |
| _version_ | 1797770533269405696 |
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| author | Katie E. Miles Bryn Hubbard Evan S. Miles Duncan J. Quincey Ann V. Rowan |
| author_facet | Katie E. Miles Bryn Hubbard Evan S. Miles Duncan J. Quincey Ann V. Rowan |
| author_sort | Katie E. Miles |
| collection | DOAJ |
| description | Characterising the structures within glaciers can give unique insight into ice motion processes. On debris-covered glaciers, traditional structural glaciological mapping is challenging because the lower glacier is hidden by the supraglacial debris layer. Here, we use high-resolution optical televiewer (OPTV) image logs from four boreholes drilled into Khumbu Glacier, Nepal, to overcome this limitation and investigate englacial structural features within a Himalayan debris-covered glacier. The OPTV logs show structural features that are up to an order of magnitude thinner than those observed at the glacier surface and reveal five structural units: (I) primary stratification of ice; (II) debris-rich planes that conform with the primary stratification; (III) water-healed crevasse traces; (IV) healed crevasse traces; and (V) steeply dipping planes of basally derived fine sediment near the glacier terminus. The OPTV logs also reveal that the primary stratification both decreases in dip with depth (by up to 56° over 20 m) and rotates with depth (by up to 100° over 20 m) towards parallelism with the proximal lateral moraine. This transformation and the presence of relict layers of basally derived sediment raised into an englacial position – possibly involving thrusting – near the glacier's now stagnant terminus reveal a previously more dynamic glacier regime. |
| first_indexed | 2024-03-12T21:23:35Z |
| format | Article |
| id | doaj.art-533457f4d0534440afcd0138887aa0c2 |
| institution | Directory Open Access Journal |
| issn | 0022-1430 1727-5652 |
| language | English |
| last_indexed | 2024-03-12T21:23:35Z |
| publishDate | 2023-08-01 |
| publisher | Cambridge University Press |
| record_format | Article |
| series | Journal of Glaciology |
| spelling | doaj.art-533457f4d0534440afcd0138887aa0c22023-07-28T10:47:45ZengCambridge University PressJournal of Glaciology0022-14301727-56522023-08-016981182210.1017/jog.2022.100Internal structure of a Himalayan debris-covered glacier revealed by borehole optical televiewingKatie E. Miles0https://orcid.org/0000-0003-2793-9766Bryn Hubbard1https://orcid.org/0000-0002-3565-3875Evan S. Miles2https://orcid.org/0000-0001-5446-8571Duncan J. Quincey3https://orcid.org/0000-0002-7602-7926Ann V. Rowan4https://orcid.org/0000-0002-3715-5554Department of Geography and Earth Sciences, Centre for Glaciology, Aberystwyth University, Aberystwyth, UKDepartment of Geography and Earth Sciences, Centre for Glaciology, Aberystwyth University, Aberystwyth, UKSwiss Federal Research Institute WSL, Birmensdorf, SwitzerlandSchool of Geography, University of Leeds, Leeds, UKDepartment of Geography, University of Sheffield, Sheffield, UK Department of Earth Science, University of Bergen and Bjerknes Centre for Climate Research, Bergen, NorwayCharacterising the structures within glaciers can give unique insight into ice motion processes. On debris-covered glaciers, traditional structural glaciological mapping is challenging because the lower glacier is hidden by the supraglacial debris layer. Here, we use high-resolution optical televiewer (OPTV) image logs from four boreholes drilled into Khumbu Glacier, Nepal, to overcome this limitation and investigate englacial structural features within a Himalayan debris-covered glacier. The OPTV logs show structural features that are up to an order of magnitude thinner than those observed at the glacier surface and reveal five structural units: (I) primary stratification of ice; (II) debris-rich planes that conform with the primary stratification; (III) water-healed crevasse traces; (IV) healed crevasse traces; and (V) steeply dipping planes of basally derived fine sediment near the glacier terminus. The OPTV logs also reveal that the primary stratification both decreases in dip with depth (by up to 56° over 20 m) and rotates with depth (by up to 100° over 20 m) towards parallelism with the proximal lateral moraine. This transformation and the presence of relict layers of basally derived sediment raised into an englacial position – possibly involving thrusting – near the glacier's now stagnant terminus reveal a previously more dynamic glacier regime.https://www.cambridge.org/core/product/identifier/S0022143022001009/type/journal_articleDebris-covered glaciersmountain glaciersstructural glaciology |
| spellingShingle | Katie E. Miles Bryn Hubbard Evan S. Miles Duncan J. Quincey Ann V. Rowan Internal structure of a Himalayan debris-covered glacier revealed by borehole optical televiewing Journal of Glaciology Debris-covered glaciers mountain glaciers structural glaciology |
| title | Internal structure of a Himalayan debris-covered glacier revealed by borehole optical televiewing |
| title_full | Internal structure of a Himalayan debris-covered glacier revealed by borehole optical televiewing |
| title_fullStr | Internal structure of a Himalayan debris-covered glacier revealed by borehole optical televiewing |
| title_full_unstemmed | Internal structure of a Himalayan debris-covered glacier revealed by borehole optical televiewing |
| title_short | Internal structure of a Himalayan debris-covered glacier revealed by borehole optical televiewing |
| title_sort | internal structure of a himalayan debris covered glacier revealed by borehole optical televiewing |
| topic | Debris-covered glaciers mountain glaciers structural glaciology |
| url | https://www.cambridge.org/core/product/identifier/S0022143022001009/type/journal_article |
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