Tsunami landfalls in the Maltese archipelago: reconciling the historical record with geomorphological evidence

Abstract

The Maltese Islands lie in the middle of the tsunamigenic Mediterranean domain, around whose margins and islands evidence of historic tsunami landfall has been increasingly recognized in recent years. Critical review of historical evidence of events in 1693 and 1908 indicates extremely modest tsunami impacts. In marked contrast, though, recently discovered geomorphological evidence summarized herein suggests that Malta's coastlines have been overwashed up to elevations of >20 m asl by an exceptional event. A new perspective is provided by a review of the central Mediterranean context within which the Maltese evidence is located. Recent advances in understanding of the Holocene sequence forming the Mediterranean Sea floor present a new stratigraphic and temporal framework within which to elucidate tsunami history. Within 100 km of Malta terrestrial stratigraphy on Sicily also provides supporting evidence of tsunami impact. Review of these advances suggests that the exceptional event required to emplace the most extreme sedimentary and geomorphological signatures on and around Malta is likely to have had a far-field origin. The currently available circumstantial evidence points strongly toward a probability that the AD365 earthquake and tsunami were responsible. This in turn enables critical reassessment of the exposure of Malta to tsunami hazard. Keywords Mediterranean; extreme waves; erosion features; boulder deposits; tsunami; Malta The Maltese archipelago sits on the Malta Plateau atop the Pelagius Platform, a northern promontory of the African plate which extends towards Sicily and separates the deep Ionian Basin from the western Mediterranean. Eastwards at a distance of 120 km the submerged Malta Escarpment forms the steep margin of the Ionian Basin, eastwards of which the sea floor falls to-4000 m (Galea 2007; Micallef et al. 2013). The islands are formed of Neogene sedimentary rocks

A Multi-Hazard Historical Catalogue for the City-Island-State of Malta (Central Mediterranean)

“…Calleja 2010) or pluvial storm flooding (Malta Resources Authority 2013) or is focused on the evidence for extreme events in the past: their causes; processes of initiation and their impacts. This has included work on past tsunamis (Biolchi et al 2016;Causon Deguara and Gauci 2017;Mottershead et al 2018) and geomorphological phenomena including landslides, rock fall, sea-arch collapses and dolines (Mantovani et al 2013;Prampolini et al 2018;Satariano and Gauci 2019;Devoto et al 2021). Recent research has not only criticised the catalogue of, and policies associated with, pluvial storm flooding, but has also highlighted that Malta is exposed to a much wider range of environmental extremes than has been commonly supposed (Jones 2018;Main et al 2018;Main 2019) In this paper and accompanying supplementary material (Table S1) we publish Malta's first multi-hazard historical catalogue in which geophysical, geomorphological and meteorological extremes are recorded, identified and in some cases inferred, from the Miocene epoch (c. 23-c. 25 Ma) to 2019 CE.…”

“…8,000 years BP, 21 July 365 CE, 4 February 1169 and 20 February 1743, impacted the coastline of the archipelago(Pareschi et al 2006;Pararas-Carayannis 2011;Biolchi et al 2016;Mottershead et al 2018;Main 2019). Conversely, the use of historical texts in relation to meteorological and geomorphological phenomena must be treated with caution as they often lack a temporal framework required for event identification and inclusion within the catalogue.…”

Clustered, Stacked and Imbricated Large Coastal Rock Clasts on Ludao Island, Southeast Taiwan, and Their Application to Palaeotyphoon Intensity Assessment

“…A recent review of possible origins for boulder deposits by Dewey et al (2021) identified five marine and non-marine mechanisms that might be responsible for their occurrence along shorelines. Of these, boulder deposits attributable to high-energy wave (HEW) action have been found in a variety of coastal settings, such as submarine forereef slopes (Etienne, 2012), beaches (Lau et al, 2015), rocky shorelines (Jones and Hunter, 1992;Paris et al, 2011), coral reef platforms (Nott, 1997;Terry et al, 2013), elevated terraces (Sussmilch, 1912;Ota et al, 2015;Mottershead et al, 2017), and cliff tops (Williams and Hall, 2004;Hall et al, 2006;Roig-Munar et al, 2018). It is understood that considerable energy is required for clast production by waves, i.e.…”

Strongly aligned coastal boulders on Ko Larn island (Thailand): a proxy for past typhoon‐driven high‐energy wave events in the Bay of Bangkok

“…Beyond tropical waters, the presence of non‐reef‐derived boulders along coastlines is also providing evidence of past HEW events, either in the context of storm or tsunami research (Cox et al ., ; Paris et al ., ; Mottershead et al ., ; Mottershead et al ., ; Salzmann & Green, ). Some non‐carbonate boulders can be dated using different techniques to their carbonate counterparts, but corroborating evidence is often needed to establish a chronology (Goff et al ., ).…”