BIBLIOS

Document type
Journal articles

Document subtype
Full paper

Title
A geological record of multiple Pleistocene tsunami inundations in an oceanic island: The case of Maio, Cape Verde

Participants in the publication
José Madeira (Author)
Dep. Geologia
IDL
Ricardo S. Ramalho (Author)
IDL
Dirk L. Hoffmann (Author)
João Mata (Author)
Dep. Geologia
IDL
Mário Moreira (Author)
INSTITUTO SUPERIOR DE ENGENHARIA DE LISBOA
IDL

Summary
In the Central Atlantic archipelagos – the Canaries, Cape Verde, Madeira and the Azores – tsunami hazard is often regarded as low, when compared with other extreme wave events such as hurricanes and storms. The geological record of many of these islands, however, suggests that tsunami hazard may be underestimated, notwithstanding being lower than in areas adjacent to subduction zones, such as the margins of the Pacific and Indian oceans. Moreover, tsunamis in\noceanic islands are generally triggered by local large-scale volcanic flank collapses, for which little is known about their frequency, making it difficult to estimate the probability of a new occurrence. Part of the problem lies in the fact that\ntsunami deposits are usually difficult to date, and few islands in the world exhibit evidence for repeated tsunami inundation on a protracted timescale. This study reports on the presence of abundant tsunami deposits (conglomerates and sandstones) on Maio Island (Cape Verde) and discusses their stratigraphy, sedimentological characteristics, probable age and tsunamigenic source. Observations indicate that four distinct inundation events of variable magnitude took\nplace during the Pleistocene. One of the tsunami deposits yielded a high-confidence U/Th age of 78.8 +- 0.9 ka, which overlaps within error with the 73.7 ka age proposed for Fogo volcano’s flank collapse, an event known to have had a significant tsunami impact on nearby Santiago Island. This shows that the Fogo tsunami also impacted Maio, resulting in runups in excess of 60 m above coeval sea-level at ca 120 km from the source. Two older deposits, possibly linked to recurrent flank collapses of the Tope de Coroa volcano in Santo Antão Island, yielded lower-confidence ages of 479 to 390 ka and 360 to 304 ka.\nA younger deposit (<78 ka) remains undated. In summary, the geological record of Maio exhibits well-preserved evidence of repeated tsunami inundation, reinforcing the notion that tsunami hazard is not so low at volcanic archipelagos featuring prominent and highly-active volcanoes such as in Cape Verde.


Where published
Sedimentology

Publication Identifiers
ISSN - 0037-0746
eISSN - 1365-3091

Publisher
Wiley



Document Identifiers
URL - http://dx.doi.org/10.1111/sed.12612
DOI - https://doi.org/10.1111/sed.12612

Rankings
Web Of Science Q1 (2020) - 4.155 - GEOLOGY - SCIE
SCIMAGO Q1 (2020) - 1.494 - Geology
SCIMAGO Q1 (2020) - 1.494 - Stratigraphy
SCOPUS Q1 (2020) - 6.2 - Stratigraphy
SCOPUS Q1 (2020) - 6.2 - Geology

Keywords
Cape Verde frequency ocean islands sediments tsunami