Glacial ripping : geomorphological evidence from Sweden for a new process of glacial erosion
In low relief Precambrian gneiss terrain in eastern Sweden, abraded bedrock surfaces were ripped apart by the Fennoscandian Ice Sheet. The resultantboulder spreadsare covers of large, angular boulders, many with glacial transport distances of 1-100 m. Boulder spreads occur alongside partly disintegr...
Published in: | Geografiska Annaler: Series A, Physical Geography |
---|---|
Main Authors: | , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Stockholms universitet, Institutionen för naturgeografi
2020
|
Subjects: | |
Online Access: | http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-183665 https://doi.org/10.1080/04353676.2020.1774244 |
id |
ftstockholmuniv:oai:DiVA.org:su-183665 |
---|---|
record_format |
openpolar |
spelling |
ftstockholmuniv:oai:DiVA.org:su-183665 2023-05-15T16:12:55+02:00 Glacial ripping : geomorphological evidence from Sweden for a new process of glacial erosion Hall, Adrian M. Krabbendam, Maarten van Boeckel, Mikis Goodfellow, Bradley W. Hättestrand, Clas Heyman, Jakob Palamakumbura, Romesh N. Stroeven, Arjen P. Näslund, Jens-Ove 2020 application/pdf http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-183665 https://doi.org/10.1080/04353676.2020.1774244 eng eng Stockholms universitet, Institutionen för naturgeografi Geografiska Annaler. Series A, Physical Geography, 0435-3676, 2020, 102:4, s. 333-353 orcid:0000-0001-8812-2253 http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-183665 doi:10.1080/04353676.2020.1774244 ISI:000545025400001 info:eu-repo/semantics/openAccess Glacial ripping groundwater overpressure Fennoscandian ice sheet Earth and Related Environmental Sciences Geovetenskap och miljövetenskap Article in journal info:eu-repo/semantics/article text 2020 ftstockholmuniv https://doi.org/10.1080/04353676.2020.1774244 2023-02-23T21:42:46Z In low relief Precambrian gneiss terrain in eastern Sweden, abraded bedrock surfaces were ripped apart by the Fennoscandian Ice Sheet. The resultantboulder spreadsare covers of large, angular boulders, many with glacial transport distances of 1-100 m. Boulder spreads occur alongside partly disintegrated roches moutonnees and associated fracture caves, and are associated withdisrupted bedrock, which shows extensive fracture dilation in the near surface. These features are distributed in ice-flow parallel belts up to 10 km wide and extend over distances of >500 km. Our hypothesis is that the assemblage results from (1) hydraulic jacking and bedrock disruption, (2) subglacial ripping and (3) displacement, transport and final deposition of boulders. Soft sediment fills indicate jacking and dilation of pre-existing bedrock fractures by groundwater overpressure below the ice sheet. Overpressure reduces frictional resistance along fractures. Where ice traction overcomes this resistance, the rock mass strength is exceeded, resulting in disintegration of rock surfaces and ripping apart into separate blocks. Further movement and deposition create boulder spreads and moraines. Short boulder transport distances and high angularity indicate that glacial ripping operated late in the last deglaciation. The depths of rock mobilized in boulder spreads are estimated as 1-4 m. This compares with 0.6-1.6 m depths of erosion during the last glaciation derived from cosmogenic nuclide inventories of samples from bedrock surfaces without evidence of disruption. Glacially disrupted and ripped bedrock is also made ready for removal by future ice sheets. Henceglacial rippingis a highly effective process of glacial erosion. Article in Journal/Newspaper Fennoscandian Ice Sheet Stockholm University: Publications (DiVA) Geografiska Annaler: Series A, Physical Geography 102 4 333 353 |
institution |
Open Polar |
collection |
Stockholm University: Publications (DiVA) |
op_collection_id |
ftstockholmuniv |
language |
English |
topic |
Glacial ripping groundwater overpressure Fennoscandian ice sheet Earth and Related Environmental Sciences Geovetenskap och miljövetenskap |
spellingShingle |
Glacial ripping groundwater overpressure Fennoscandian ice sheet Earth and Related Environmental Sciences Geovetenskap och miljövetenskap Hall, Adrian M. Krabbendam, Maarten van Boeckel, Mikis Goodfellow, Bradley W. Hättestrand, Clas Heyman, Jakob Palamakumbura, Romesh N. Stroeven, Arjen P. Näslund, Jens-Ove Glacial ripping : geomorphological evidence from Sweden for a new process of glacial erosion |
topic_facet |
Glacial ripping groundwater overpressure Fennoscandian ice sheet Earth and Related Environmental Sciences Geovetenskap och miljövetenskap |
description |
In low relief Precambrian gneiss terrain in eastern Sweden, abraded bedrock surfaces were ripped apart by the Fennoscandian Ice Sheet. The resultantboulder spreadsare covers of large, angular boulders, many with glacial transport distances of 1-100 m. Boulder spreads occur alongside partly disintegrated roches moutonnees and associated fracture caves, and are associated withdisrupted bedrock, which shows extensive fracture dilation in the near surface. These features are distributed in ice-flow parallel belts up to 10 km wide and extend over distances of >500 km. Our hypothesis is that the assemblage results from (1) hydraulic jacking and bedrock disruption, (2) subglacial ripping and (3) displacement, transport and final deposition of boulders. Soft sediment fills indicate jacking and dilation of pre-existing bedrock fractures by groundwater overpressure below the ice sheet. Overpressure reduces frictional resistance along fractures. Where ice traction overcomes this resistance, the rock mass strength is exceeded, resulting in disintegration of rock surfaces and ripping apart into separate blocks. Further movement and deposition create boulder spreads and moraines. Short boulder transport distances and high angularity indicate that glacial ripping operated late in the last deglaciation. The depths of rock mobilized in boulder spreads are estimated as 1-4 m. This compares with 0.6-1.6 m depths of erosion during the last glaciation derived from cosmogenic nuclide inventories of samples from bedrock surfaces without evidence of disruption. Glacially disrupted and ripped bedrock is also made ready for removal by future ice sheets. Henceglacial rippingis a highly effective process of glacial erosion. |
format |
Article in Journal/Newspaper |
author |
Hall, Adrian M. Krabbendam, Maarten van Boeckel, Mikis Goodfellow, Bradley W. Hättestrand, Clas Heyman, Jakob Palamakumbura, Romesh N. Stroeven, Arjen P. Näslund, Jens-Ove |
author_facet |
Hall, Adrian M. Krabbendam, Maarten van Boeckel, Mikis Goodfellow, Bradley W. Hättestrand, Clas Heyman, Jakob Palamakumbura, Romesh N. Stroeven, Arjen P. Näslund, Jens-Ove |
author_sort |
Hall, Adrian M. |
title |
Glacial ripping : geomorphological evidence from Sweden for a new process of glacial erosion |
title_short |
Glacial ripping : geomorphological evidence from Sweden for a new process of glacial erosion |
title_full |
Glacial ripping : geomorphological evidence from Sweden for a new process of glacial erosion |
title_fullStr |
Glacial ripping : geomorphological evidence from Sweden for a new process of glacial erosion |
title_full_unstemmed |
Glacial ripping : geomorphological evidence from Sweden for a new process of glacial erosion |
title_sort |
glacial ripping : geomorphological evidence from sweden for a new process of glacial erosion |
publisher |
Stockholms universitet, Institutionen för naturgeografi |
publishDate |
2020 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-183665 https://doi.org/10.1080/04353676.2020.1774244 |
genre |
Fennoscandian Ice Sheet |
genre_facet |
Fennoscandian Ice Sheet |
op_relation |
Geografiska Annaler. Series A, Physical Geography, 0435-3676, 2020, 102:4, s. 333-353 orcid:0000-0001-8812-2253 http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-183665 doi:10.1080/04353676.2020.1774244 ISI:000545025400001 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1080/04353676.2020.1774244 |
container_title |
Geografiska Annaler: Series A, Physical Geography |
container_volume |
102 |
container_issue |
4 |
container_start_page |
333 |
op_container_end_page |
353 |
_version_ |
1765998521632161792 |