eprintid: 10091454 rev_number: 14 eprint_status: archive userid: 608 dir: disk0/10/09/14/54 datestamp: 2020-02-20 11:19:10 lastmod: 2020-02-20 11:19:10 status_changed: 2020-02-20 11:19:10 type: article metadata_visibility: show creators_name: Kavanagh, JL creators_name: Burns, AJ creators_name: Hilmi Hazim, S creators_name: Wood, EP creators_name: Martin, SA creators_name: Hignett, S creators_name: Dennis, DJC title: Challenging dyke ascent models using novel laboratory experiments: Implications for reinterpreting evidence of magma ascent and volcanism ispublished: pub divisions: UCL divisions: A01 divisions: B04 divisions: C05 divisions: F48 keywords: Magma flow, Host-rock deformation, Dyke, Analogue experiment, Particle image velocimetry, Digital image correlation note: Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). abstract: Volcanic eruptions are fed by plumbing systems that transport magma from its source to the surface, mostly fed by dykes. Here we present laboratory experiments that model dyke ascent to eruption using a tank filled with a crust analogue (gelatine, which is transparent and elastic) that is injected from below by a magma analogue (dyed water). This novel experimental setup allows, for the first time, the simultaneous measurement of fluid flow, sub-surface and surface deformation during dyke ascent. During injection, a penny-shaped fluid-filled crack is formed, intrudes, and traverses the gelatine slab vertically to then erupt at the surface. Polarised light shows the internal stress evolution as the dyke ascends, and an overhead laser scanner measures the surface elevation change in the lead-up to dyke eruption. Fluorescent passive-tracer particles that are illuminated by a laser sheet are monitored, and the intruding fluid's flow dynamics and gelatine's sub-surface strain evolution is measured using particle image velocimetry and digital image correlation, respectively. We identify 4 previously undescribed stages of dyke ascent. Stage 1, early dyke growth: the initial dyke grows from the source, and two fluid jets circulate as the penny-shaped crack is formed. Stage 2, pseudo-steady dyke growth: characterised by the development of a rapidly uprising, central, single pseudo-steady fluid jet, as the dyke grows equally in length and width, and the fluid down-wells at the dyke margin. Sub-surface host strain is localised at the head region and the tail of the dyke is largely static. Stage 3, pre-eruption unsteady dyke growth: an instability in the fluid flow appears as the central fluid jet meanders, the dyke tip accelerates towards the surface and the tail thins. Surface deformation is only detected in the immediate lead-up to eruption and is characterised by an overall topographic increase, with axis-symmetric topographic highs developed above the dyke tip. Stage 4 is the onset of eruption, when fluid flow is projected outwards and focused towards the erupting fissure as the dyke closes. A simultaneous and abrupt decrease in sub-surface strain occurs as the fluid pressure is released. Our results provide a comprehensive physical framework upon which to interpret evidence of dyke ascent in nature, and suggest dyke ascent models need to be re-evaluated to account for coupled intrusive and extrusive processes and improve the recognition of monitoring signals that lead to volcanic eruptions in nature. date: 2018-04 date_type: published publisher: Elsevier BV official_url: https://doi.org/10.1016/j.jvolgeores.2018.01.002 oa_status: green full_text_type: pub language: eng primo: open primo_central: open_green verified: verified_manual elements_id: 1755637 doi: 10.1016/j.jvolgeores.2018.01.002 lyricists_name: Burns, Alec lyricists_id: ABURN42 actors_name: Burns, Alec actors_id: ABURN42 actors_role: owner full_text_status: public publication: Journal of Volcanology and Geothermal Research volume: 354 pagerange: 87-101 citation: Kavanagh, JL; Burns, AJ; Hilmi Hazim, S; Wood, EP; Martin, SA; Hignett, S; Dennis, DJC; (2018) Challenging dyke ascent models using novel laboratory experiments: Implications for reinterpreting evidence of magma ascent and volcanism. Journal of Volcanology and Geothermal Research , 354 pp. 87-101. 10.1016/j.jvolgeores.2018.01.002 <https://doi.org/10.1016/j.jvolgeores.2018.01.002>. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/10091454/1/1-s2.0-S0377027317304602-main.pdf