Marine Investigations of Greece\u27s Santorini Volcanic Field

The most recent major explosive eruption of the Santorini volcano in Greece—around 3600 years before present (B.P.), often referred to as the Minoan eruption—is one of the largest volcanic events known in historical time and has been the subject of intense volcanological and archeological studies [Druitt et al., 1999]. The submarine volcano Kolumbo, located seven kilometers northeast of Santorini and associated with Santorini\u27s tectonic system, erupted explosively in 1650 A.D., resulting in fatalities on the island of Thera [Fouqué, 1879]. A large fraction of the erupted products from the Minoan eruption has been deposited in the sea but, up to now, only has been studied in distal marine sediments. As part of a collaborative project between the University of Rhode Island (Narragansett), the Hellenic Centre of Marine Research (Athens, Greece), and the Institute of Geology and Mineral Exploration (Athens), a marine geological survey was conducted around Santorini from April to June 2006. he new work now shows that the volume of the Minoan eruption may be comparable to that of the largest known historical eruption, the 1815 eruption of Tambora in Indonesia [Sigurdsson and Carey, 1989]; provides insights into the depositional processes and size of the Minoan eruption; and led to the discovery of important submarine hydrothermal vents with active mineralization

Tsunami triggering mechanisms associated with the 17th cent. BC Minoan eruption of thera Volcano, Greece

Systematic seismic profiling and swath bathymetry of the seafloor around Santorini volcanic field, including the caldera, shed light to the structure and seismic stratigraphy of the accumulated volcanic deposits and the mechanisms which may have led to the generation of one or multiple tsunamis during the Minoan eruption. We propose that tsunamis may have been triggered by two distinct processes associated with the Minoan eruption: (i) Massive pyroclastic flows entering the ocean around the islands of Santorini. The total volume of the pyroclastic flow deposits on the seafloor around Santorini is about 54.5 km3. (ii) The collapse of the Minoan volcanic edifice below the sea-level created new space of minimum volume 4.5-5 km3 between the sea-level and the 200m depth contour. The total volume created may exceeded 10 km3. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE)

The Santorini-Amorgos Shear Zone: Evidence for Dextral Transtension in the South Aegean Back-Arc Region, Greece

Bathymetric and seismic data provide insights into the geomorphological configuration, seismic stratigraphy, structure, and evolution of the area between Santorini, Amorgos, Astypalea, and Anafi islands. Santorini-Amorgos Shear Zone (SASZ) is a NE-SW striking feature that includes seven basins, two shallow ridges, and hosts the volcanic centers of Santorini and Kolumbo. The SASZ initiated in the Early Pliocene as a single, W-E oriented basin. A major reorganization of the geodynamic regime led to (i) reorientation of the older faults and initiation of NE-SW striking ones, (ii) disruption of the single basin and localized subsidence and uplift, (iii) creation of four basins out of the former single one (Anafi, Amorgos South, Amorgos North, and Kinairos basins), (iv) rifting of the northern and southern margins and creation of Anydros, Astypalea North, and Astypalea South basins, and (v) uplift of the ridges. Dextral shearing and oblique rifting are accommodated by NE-SW striking, dextral oblique to strike-slip faults and by roughly W-E striking, normal, transfer faults. It is suggested here that enhanced shearing in NE-SW direction and oblique rifting may be the dominant deformation mechanism in the South Aegean since Early Quaternary associated with the interaction of North Anatolian Fault with the slab roll-back

Ultra-high resolution paleoceanography and paleoclimatology during sapropel S1 deposition in the NE Aegean Sea (South Limnos basin) and comparison with NE Limnos Island coastal plain sediment records: evidence of Black Sea inflow establishment

International audienc

Assessment of the physical impact of a short-term dredging operation on a semi-enclosed environment: South Euboean Gulf, Greece

The potential influence of short-period (May-June 2012) dredging activities (for the installation of a submarine gas pipeline) on physical properties of the marine environment of two shallow-water sites in the Aliveri and Varnavas areas of South Euboean Gulf (Greece) has been evaluated. During the dredging operation in Varnavas, the induced dredge plume traveled up to 750 m from the shoreline, featured by light attenuation coefficient (c(p)) maxima of 4.01-4.61 m(-1) and suspended particulate matter (SPM) concentrations up to 6.01 mg L-1. After dredging the previous parameters reduced to the ambient seawater condition, 0.45 m(-1) and < 2.8 mg L-1 on average, respectively. Likewise in Aliveri, the dredging-associated sediment plume drifted offshore up to 400 m from the shoreline, characterized by c(p) maxima of 2.11-4.86 m(-1) and SPM concentrations up to 13.07 mg L-1. After the completion of the excavation and trenching activities, the c(p) and SPM values were restored to the pre-disturbance condition, 0.6 m(-1) and < 2.2 mg L-1 on average, respectively. The migration of the dredge plume in both dredging sites was accomplished through the formation of intermediate and benthic nepheloid layers, whose development and evolution were governed by seawater stratification and flow regime. The dredging-derived SPM levels appeared to increase within a distance of no more than 300 m from the shoreline (near-field zone). Based on data from the literature, this SPM enhancement together with the deposition of a post-dredging residual mud veneer in the near-field zone could deteriorate local marine biota, but in a reversible way

Climate variability in the Eastern and Western Mediterranean Sea over the last two millennia: a contribution of PaleoMex/MISTRALS

International audienceRecent compilations of Mediterranean 2k paleoclimate archives (Luterbacher et al., 2012, MedClivar Book) stressed the lack of high-resolution/ continuous marine records. The two new high-resolution sea surface temperature (SSTs) time-series presented here from the shallow coastal shelf sediments of the Gulf of Lions and deeper ocean one of the Aegean Sea using alkenone paleothermometry, are thus an important contribution. SST values are roughly 2°C warmer in the Eastern than Western Mediterranean sites in agreement with our knowledge of the production pattern of the main alkenone producer Emiliania huxleyi in the two basins. Both SST-record reveal significant variability of cool/warm intervals, corresponding to the continental European and Northern Hemisphere climatic variability. While distant from each other, SSTs at the two sites show some degree of similarity: increasing SSTs from ~ 600 to 1300 AD followed by a significant cooling till the early 1600's marking the onset of an outstanding warm period reaching values similar to present day. After a sharp decrease ending around 1700 yrs AD, the last three centuries indicate gradually rising SSTs by about 1°C/100 yrs. To our knowledge the latter feature has been undocumented in North Atlantic cores but often observed in paleoclimate reconstructions of the European climate, though with different regional timing and amplitude. This unexpected finding may reflect feedbacks from the surrounding land-masses contributing to "continentalize" the Mediterranean climate. Another notable feature is the short-lived abrupt cooling in the Aegean record between 1816 and 1824 yr AD, possibly expressing the surface water cooling subsequent to the Tambora volcanic eruption of 1815 yrs AD. * We acknowledge financial support from MEDECOS (Marin-ERA, EU/FP6) Project and the Greek General Secretary of Research and Technology. Luterbacher J, Garcia-Herrera R, Allan R, Alvarez-Castro BG, Benito G, Booth J, Büntgen U, Colombaroli D, Davis B, Esper J, Felis T, Fleitmann D, Frank D, Gallego D, Gonzalez-Rouco FJ, Goosse H, Kiefer T, Macklin MG, Montagna P, Newmann L, Rath V, Ribera P, Roberts N, Silenzi S, Tinner W, Valero-Garces B, van der Schrier G, Vanniere B, Wanner H, Werner JP, Willett G, Xoplaki E, Zerefos CS, Zorita E (2012) A review of 2000 years of paleoclimatic evidence in the Mediterranean. In: Lionello, P. (Ed.), The Climate of the Mediterranean region: From the Past to the Future. Elsevier, Amsterdam, 87-185

Searching for Neolithic sites in the Bay of Kiladha, Greece

Since the excavations at Franchthi Cave in the 1960s and 1970s, the possibility of finding a submerged Neolithic site in the Bay of Kiladha has been discussed. Initial research, based on marine geophysical survey and core sampling, brought contrasted results. Starting in 2012, new parts of the Bay were investigated, using different techniques and improved methods, such as geological-geophysical survey, further core sampling (including the finding of artefacts and anthropogenic indicators of a given date in the cores), shallow water ERT (with an adapted methodology), and underwater excavation. The combined evidence leads to a reconsideration of previous work, to the discovery of submerged structures directly off the cave, which might well be Neolithic walls, and points to the existence of two new submerged sites, one dating to the Neolithic, in the middle of the Bay, and the other to the Final Neolithic/Early Bronze Age I, at Lambayanna. The implications of these findings are discussed as well