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How hazardous are tsunamis triggered by small-scale mass-wasting events on volcanic islands? New insights from Madeira – NE Atlantic

Omira, R., Baptista, M. A., Quartau, R., Ramalho, R. S., Kim, J., Ramalho, I. and Rodrigues, A. 2022. How hazardous are tsunamis triggered by small-scale mass-wasting events on volcanic islands? New insights from Madeira – NE Atlantic. Earth and Planetary Science Letters 578 , 117333. 10.1016/j.epsl.2021.117333

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Abstract

Mass-wasting events are a key process in the evolution of volcanic ocean islands. They occur at various dimensional scales and present a major source of hazard. When the collapsed material plunges into the sea, destructive tsunamis can be generated. Yet, the hazard potential of collapse-induced tsunamis is still poorly understood with different opinions on what consequences to expect from this type of events, particularly those related to massive volcanic island flank collapses. In this paper, however, we explore the hazard extent of tsunamis triggered by the smaller – but more frequent – coastal cliff-failures, in order to isolate critical factors in the generation, propagation and impact of these tsunamis. To achieve this, we use the prime example of Madeira, a volcanic island in the Atlantic Ocean highly vulnerable to cliff-failure. Particularly, we explore the March 4th, 1930 Cabo Girão event that triggered a deadly tsunami. The coastal impact of the 1930 “Deadly Wave”, as the island's inhabitants referred to the generated tsunami, resulted in 19 fatalities. We use historical description, morphological analysis, and numerical modelling to better understand the tsunamigenesis of tall island cliffs failing into the sea. Interestingly, we find that a relatively small-scale mass-wasting event (∼0.003 km3 volume) was the cause of the reported tsunami that inundated the nearest coasts. Our numerical results, fairly agreeing with the available collapse and subsequent tsunami descriptions, suggest that the tsunami impact was mainly localized on the southern coast of Madeira Island. Furthermore, our study allows proposing a novel morphology-based conceptional model for the tsunamigenesis and hazard extent induced by mass-wasting events on oceanic volcanic islands.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Environmental Sciences
Publisher: Elsevier
ISSN: 0012-821X
Date of First Compliant Deposit: 16 December 2021
Date of Acceptance: 4 December 2021
Last Modified: 07 Nov 2023 06:33
URI: https://orca.cardiff.ac.uk/id/eprint/146179

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