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  • 1
    Publication Date: 2016-03-16
    Description: The accumulation of large boulders related to waves generated by either tsunamis or extreme storm events have been observed in different areas of the Mediterranean Sea. Along the eastern low-lying rocky coasts of Malta, five sites with large boulder deposits have been investigated, measured and mapped. These boulders have been detached and moved from the nearshore and the lowest parts of the coast by sea wave action. In the Sicily–Malta channel, heavy storms are common and originate from the NE and NW winds. Conversely, few tsunamis have been recorded in historical documents to have reached the Maltese archipelago. We present a multi-disciplinary study, which aims to define the characteristics of these boulder accumulations, in order to assess the coastal geo-hazard implications triggered by the sheer ability of extreme waves to detach and move large rocky blocks inland. The wave heights required to transport 77 coastal boulders were calculated using various hydrodynamic equations. Particular attention was given to the quantification of the input parameters required in the workings of these equations, such as size, density and distance from the coast. In addition, accelerator mass spectrometry (AMS) 14C ages were determined from selected samples of marine organisms encrusted on some of the coastal boulders. The combination of the results obtained both by the hydrodynamic equations, which provided values comparable with those observed and measured during the storms, and radiocarbon dating suggests that the majority of the boulders have been detached and moved by intense storm waves. These boulders testify to the existence of a real hazard for the coasts of Malta, i.e. that of very high storm waves, which, during exceptional storms, are able to detach large blocks of volumes exceeding 10 m3 from the coastal edge and the nearshore bottom, and also to transport them inland. Nevertheless, the occurrence of one or more tsunami events cannot be ruled out, since radiocarbon dating of some marine organisms did reveal ages which may be related to historically known tsunamis in the Mediterranean region, such as the ones in AD 963, 1329, 1693 and 1743.
    Print ISSN: 1561-8633
    Electronic ISSN: 1684-9981
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 2
    Publication Date: 2022-02-18
    Description: The Mediterranean Basin is characterized by a significant variability in tectonic behaviour, ranging from subsidence to uplifting. However, those coastal areas considered to be tectonically stable show coastal landforms at elevations consistent with eustatic and isostatic sea level change models. In particular, geomorphological indicators—such as tidal notches or shore platforms—are often used to define the tectonic stability of the Mediterranean coasts. We present the results of swim surveys in nine rocky coastal sectors in the central Mediterranean Sea using the Geoswim approach. The entire route was covered in 22 days for a total distance of 158.5 km. All surveyed sites are considered to have been tectonically stable since the last interglacial (Marine Isotope Stage 5.5 [MIS 5.5]), because related sea level markers fit well with sea level rise models. The analysis of visual observations and punctual measurements highlighted that, with respect to the total length of surveyed coast, the occurrence of tidal notches, shore platforms, and other indicators accounts for 85% of the modern coastline, and only 1% of the MIS 5.5 equivalent. Therefore, only 1% of the surveyed coast showed the presence of fossil markers of paleo sea levels above the datum. This significant difference is mainly attributable to erosion processes that did not allow the preservation of the geomorphic evidence of past sea level stands. In the end, our research method showed that the feasibility of applying such markers to define long-term tectonic behaviour is much higher in areas where pre-modern indicators have not been erased, such as at sites with hard bedrock previously covered by post-MIS 5.5 continental deposits, e.g., Sardinia, the Egadi Islands, Ansedonia, Gaeta, and Circeo. In general, the chances of finding such preserved indicators are very low.
    Description: Published
    Description: 2127
    Description: 4A. Oceanografia e clima
    Description: 7A. Geofisica per il monitoraggio ambientale
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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