Fractures in a trachyandesitic lava at Öræfajökull, Iceland, used to infer subglacial emplacement in 1727–8 eruption
We present detailed field observations of cooling fractures in a small-volume trachyandesitic lava, informally named the Slaga lava, on the south west flank of Öræfajökull volcano, south east Iceland. Columnar joints, pseudopillow fracture systems, and curved platy jointing occur in the lava, whose...
Published in: | Journal of Volcanology and Geothermal Research |
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Online Access: | https://eprints.lancs.ac.uk/id/eprint/71380/ https://doi.org/10.1016/j.jvolgeores.2014.10.004 |
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ftulancaster:oai:eprints.lancs.ac.uk:71380 2023-08-27T04:09:36+02:00 Fractures in a trachyandesitic lava at Öræfajökull, Iceland, used to infer subglacial emplacement in 1727–8 eruption Forbes, Anne E.S. Blake, Steven Tuffen, Hugh Wilson, Andrew 2014-11-01 https://eprints.lancs.ac.uk/id/eprint/71380/ https://doi.org/10.1016/j.jvolgeores.2014.10.004 unknown Forbes, Anne E.S. and Blake, Steven and Tuffen, Hugh and Wilson, Andrew (2014) Fractures in a trachyandesitic lava at Öræfajökull, Iceland, used to infer subglacial emplacement in 1727–8 eruption. Journal of Volcanology and Geothermal Research, 288. pp. 8-18. ISSN 0377-0273 Journal Article PeerReviewed 2014 ftulancaster https://doi.org/10.1016/j.jvolgeores.2014.10.004 2023-08-03T22:26:48Z We present detailed field observations of cooling fractures in a small-volume trachyandesitic lava, informally named the Slaga lava, on the south west flank of Öræfajökull volcano, south east Iceland. Columnar joints, pseudopillow fracture systems, and curved platy jointing occur in the lava, whose exposed section is approximately 600 m in length and generally 2–3 m in thickness. Columnar jointing may occur at the base of flow lobes, whereas pseudopillow fracture systems occur throughout the lava in an outer, glassy, fractured carapace, and curved platy fractures occur in the centres of larger flow lobes. Pseudopillow fracture systems, composed of a single master fracture and multiple subsidiary fractures formed normal to the master fracture, are of two types: G-type pseudopillow fracture systems have very narrow striae (chisel marks) on their master fractures, indicative of rapid cooling and brittle fracture; SR-type pseudopillow fracture systems display alternating smooth and rough master fracture surface textures, evidence of alternating brittle and ductile fracture propagation mechanisms. Subsidiary fractures in both types show curved striae on their fracture surfaces, which enable the determination of fracture propagation directions. Pseudopillow fracture systems are thought only to form in the presence of water, including water caused by the melting of ice and snow. The curved platy fractures display prominent river lines and may have resulted from cooling contraction, post-emplacement degassing, flow deflation or shearing in the flow against the outer solid crust of the flow during inflation. Due to recent advances in the understanding of the formation mechanisms of pseudopillow fractures systems they, and the other fractures present in the flow, can be used to reconstruct the cooling environment. The lava is inferred to have been emplaced within subglacial drainage channels incised into or beneath a thin alpine-type glacier, with coolant infiltrating the lava radially from all sides and ponding or ... Article in Journal/Newspaper glacier Iceland Lancaster University: Lancaster Eprints Slaga ENVELOPE(-16.767,-16.767,63.939,63.939) Journal of Volcanology and Geothermal Research 288 8 18 |
institution |
Open Polar |
collection |
Lancaster University: Lancaster Eprints |
op_collection_id |
ftulancaster |
language |
unknown |
description |
We present detailed field observations of cooling fractures in a small-volume trachyandesitic lava, informally named the Slaga lava, on the south west flank of Öræfajökull volcano, south east Iceland. Columnar joints, pseudopillow fracture systems, and curved platy jointing occur in the lava, whose exposed section is approximately 600 m in length and generally 2–3 m in thickness. Columnar jointing may occur at the base of flow lobes, whereas pseudopillow fracture systems occur throughout the lava in an outer, glassy, fractured carapace, and curved platy fractures occur in the centres of larger flow lobes. Pseudopillow fracture systems, composed of a single master fracture and multiple subsidiary fractures formed normal to the master fracture, are of two types: G-type pseudopillow fracture systems have very narrow striae (chisel marks) on their master fractures, indicative of rapid cooling and brittle fracture; SR-type pseudopillow fracture systems display alternating smooth and rough master fracture surface textures, evidence of alternating brittle and ductile fracture propagation mechanisms. Subsidiary fractures in both types show curved striae on their fracture surfaces, which enable the determination of fracture propagation directions. Pseudopillow fracture systems are thought only to form in the presence of water, including water caused by the melting of ice and snow. The curved platy fractures display prominent river lines and may have resulted from cooling contraction, post-emplacement degassing, flow deflation or shearing in the flow against the outer solid crust of the flow during inflation. Due to recent advances in the understanding of the formation mechanisms of pseudopillow fractures systems they, and the other fractures present in the flow, can be used to reconstruct the cooling environment. The lava is inferred to have been emplaced within subglacial drainage channels incised into or beneath a thin alpine-type glacier, with coolant infiltrating the lava radially from all sides and ponding or ... |
format |
Article in Journal/Newspaper |
author |
Forbes, Anne E.S. Blake, Steven Tuffen, Hugh Wilson, Andrew |
spellingShingle |
Forbes, Anne E.S. Blake, Steven Tuffen, Hugh Wilson, Andrew Fractures in a trachyandesitic lava at Öræfajökull, Iceland, used to infer subglacial emplacement in 1727–8 eruption |
author_facet |
Forbes, Anne E.S. Blake, Steven Tuffen, Hugh Wilson, Andrew |
author_sort |
Forbes, Anne E.S. |
title |
Fractures in a trachyandesitic lava at Öræfajökull, Iceland, used to infer subglacial emplacement in 1727–8 eruption |
title_short |
Fractures in a trachyandesitic lava at Öræfajökull, Iceland, used to infer subglacial emplacement in 1727–8 eruption |
title_full |
Fractures in a trachyandesitic lava at Öræfajökull, Iceland, used to infer subglacial emplacement in 1727–8 eruption |
title_fullStr |
Fractures in a trachyandesitic lava at Öræfajökull, Iceland, used to infer subglacial emplacement in 1727–8 eruption |
title_full_unstemmed |
Fractures in a trachyandesitic lava at Öræfajökull, Iceland, used to infer subglacial emplacement in 1727–8 eruption |
title_sort |
fractures in a trachyandesitic lava at öræfajökull, iceland, used to infer subglacial emplacement in 1727–8 eruption |
publishDate |
2014 |
url |
https://eprints.lancs.ac.uk/id/eprint/71380/ https://doi.org/10.1016/j.jvolgeores.2014.10.004 |
long_lat |
ENVELOPE(-16.767,-16.767,63.939,63.939) |
geographic |
Slaga |
geographic_facet |
Slaga |
genre |
glacier Iceland |
genre_facet |
glacier Iceland |
op_relation |
Forbes, Anne E.S. and Blake, Steven and Tuffen, Hugh and Wilson, Andrew (2014) Fractures in a trachyandesitic lava at Öræfajökull, Iceland, used to infer subglacial emplacement in 1727–8 eruption. Journal of Volcanology and Geothermal Research, 288. pp. 8-18. ISSN 0377-0273 |
op_doi |
https://doi.org/10.1016/j.jvolgeores.2014.10.004 |
container_title |
Journal of Volcanology and Geothermal Research |
container_volume |
288 |
container_start_page |
8 |
op_container_end_page |
18 |
_version_ |
1775351108930109440 |