Moore, Lily Clare (2024) Geology Investigating the structural and mechanical properties involved in catastrophic volcanic collapse. PhD thesis, Birkbeck, University of London.
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Abstract
Volcanic collapses occur globally across a range of volcanic settings with an occurrence rate of five events per century. Collapse events are extremely destructive and can be tsunamigenic. The 2018 collapse and tsunami involving Anak Krakatau highlights the potential impacts of these events. Studying volcanic collapse scars with evidence of tsunamis is critical to further understanding the possible causes of instability. This thesis studies two examples of tsunamigenic volcanic collapse of different scales and volcanic setting: Ritter Island (Papua New Guinea) and Fogo (Cape Verde). Drone surveys and structure from motion (SfM) modelling is used to create high resolution 3D models of both these collapse scars. These datasets provide improved detail about the island’s structure. Samples from these collapse scars have been measured to determine the range of mechanical and hydraulic properties of the rocks making up the edifice including porosity, permeability and uniaxial compressive strengths. These properties are then discussed with the geomorphological analysis to examine how the pre-collapse volcano may have developed instabilities contributing to collapse. Results include an updated estimate on the collapsed volume for Ritter Island of 3.7 km3. At Ritter, compressive strengths were 50% lower in lava samples affected by alteration identifying this as a possible weakening mechanism. At Fogo, pyroclastic layers have been identified as weakest material within the edifice. Dyke orientation analysis at both volcanoes has highlighted similar trends in intrusions perpendicular to the direction of collapse. This similarity in the intrusion pattern across the two edifices suggests this could be a common weakening mechanism. These results are important in the field of hazard assessment and monitoring. Improved pre-collapse reconstructions and volumes directly impact on tsunami modelling. Also, monitoring of the type and extent of alteration as well as intrusion emplacement orientation and flank movement can help identify unstable edifices.
Metadata
| Item Type: | Thesis |
|---|---|
| Copyright Holders: | The copyright of this thesis rests with the author, who asserts his/her right to be known as such according to the Copyright Designs and Patents Act 1988. No dealing with the thesis contrary to the copyright or moral rights of the author is permitted. |
| Depositing User: | Acquisitions And Metadata |
| Date Deposited: | 13 Nov 2024 11:30 |
| Last Modified: | 13 Nov 2024 15:36 |
| URI: | https://eprints.bbk.ac.uk/id/eprint/54537 |
| DOI: | https://doi.org/10.18743/PUB.00054537 |
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