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SCIENTIFIC OUTLINE

The scientific and research priorities of the Department of Marine Geology & Geophysics are largely defined by the unique geodynamic regime of the broader Hellenic region, the Eastern Mediterranean and the Black Sea. The movements of all blocks of the region in nearly all directions result in the development of significant, active geological structures, and control the evolution of multivariant geo-processes along both their boundaries, and their in interior. Building up of stresses due to the varied plate and block motions causes brittle deformation in the upper crusts, expressed with frequent, large earthquakes, and plastic deformation in the lower crust. Numerous, active faults and fault zones separate regions of tectonic uplift, where erosion prevails, from regions of rapid subsidence.

This complex geodynamic regime triggers. or favours. the development of numerous geological processes and phenomena like:

• Positive/negative changes of the morphological relief, associated with tectonic movements and/or erosion/deposition
• Volcanic activity and associated phenomena
• Development of varied sedimentary environments (delta evolution, coastal zones, clastic and carbonate sedimentation, turbidites and gravity processes, etc)
• Geochemical processes related to distinct sedimentary environments or fluid flow ascending through zones of weakness (faults)
• Mud volcanism and cold seeping phenomena, related to gas hydrate formation

In addition to these endogenic processes, mega climate changes in the recent geologic history have seriously influenced the evolution of various geologic processes, particularly through the dramatic sea-level changes. On top of that, rapidly growing anthropogenic activities and impacts drastically affect ongoing processes, making the harmonic interaction between nature and mankind a difficult task and turning geological hazards into catastrophic risks.

RESEARCH OBJECTIVES

The main basic and applied research objectives of the Department of Marine Geology- & Geophysics fall into the following fields:

Coastal and offshore sedimentary environments – Erosion/deposition processes

Sedimentary processes constitute the main dynamic parameter positively or negatively affecting the seafloor, from the coastal zone and the shallow shelf, to the submarine slopes and the deep basins. Study and monitoring of sediment accumulation and erosion mechanisms in various environments and their interplay with anthropogenic activities and vice versa constitutes a major objective currently addressed by the Marine Geology-Geophysics Department.

Coastal zone dynamics includes all physical processes taking place at the land-ocean interface and is a major issue affecting large populations all around the world. Numerous parts of the long Greek coastline receive strong environmental pressures due to manifold, rapidly increasing amount of anthropogenic activities. Coastal erosion has progressively become a very common phenomenon, which in many cases has been initiated by inappropriate interventions and constructions. One of the most important objectives in this topic is the mitigation of coastal erosion effects through the adaptation of the anthropogenic activities to the natural processes. Of particular interest is the waterfront of coastal alluvial plains, which exhibit extensive economic, touristic and urban development. They constitute the terrestrial part of larger deltas, developed both on land and offshore, the evolution of which is directly controlled by the interaction of terrestrial and marine processes.

The seafloor of the Aegean and Ionian Seas display spectacular morphological irregularities. Steep slopes, developed along active faults, separate narrow shelves from relatively small, commonly elongate deep basins. Steep slopes constitute the favourable regions for the occurrence of gravity-driven phenomena (e.g. slumping and sliding, gravity and turbidity flows). Submarine landslides are usually spatially associated with large active faults. Most of the known historical tsunamis in this region are believed to have been triggered by landslides associated or not with earthquakes. Systematic swath bathymetric and seismic profiling surveys along with advanced geotechnical laboratory analyses aim at recognizing potential unstable submarine slopes and estimating landslide vulnerability.

Sedimentary sequences deposited in submarine basins constitute an excellent, complete archive of tectonic movements, climate changes, sea-level changes, environmental crises, landslides, volcanic eruptions, variations in the carbon cycle. Reconstruction of past geological events and environmental changes through the decoding of the sedimentary archive improves our understanding of active processes. Extraction of this information requires the use of integrated geophysical, geochemical, palaeontological, isotopic methods and advanced laboratory techniques like measurements of isotopic activities (²¹⁰Pb, U-Th, ¹³⁷Cs, ²²⁶Ra, ⁷Be), rare earth analyses, organic indexes etc.

A major initiative of the Marine Geology-Geophysics department is devoted to the Palaeo-oceanographic research of the environmentally sensitive Eastern Mediterranean Region. The periodic formation of sapropel layers points to repeated environmental crises in the recent geological history. Advanced techniques are being applied for the investigation and monitoring of the actual sedimentary processes (transport, suspension, deposition, resuspension), which can be used to reconstruct past sedimentary mechanisms.

Geodynamic evolution and associated geotectonic processes

The primary research topics are: investigation and mapping of active faults, monitoring of seismicity and estimation of seismic hazard, and multidisciplinary survey of submarine hydrothermal and volcanic activity.

Large or small, active/seismic faults and fault zones constitute the most sound elements of the Active Neotectonic Structure of the region, and are directly associated with earthquake activity and the development of most of the known marine geological hazards (submarine landslides and tsunamis). Detailed investigation into the geometrical and kinematic characteristics of individual faults together with serious attempts to reconstruct recent movements on fault planes on the seafloor by using state of the art, high-resolution marine geological-geophysical and marine paleoseismological methods contribute to a drastic improvement of offshore seismic hazard estimation. Large scale bathymetric mapping of the seafloor along with high resolution surveys are an absolute prerequisite for the understanding of submarine geomorphological processes.

Cold seeping and related fluid flow through weak zones are of particular interest since they constitute a major factor in important geological processes. Fluid flow and pressure along active faults are believed to be directly related to earthquake triggering. Cold seeping occurs at various places on the seafloor and is associated with extreme environments, mud volcanism and gas hydrate formation. The latter is considered as a potential source of methane gas, which may also constitute a potential source of greenhouse gases, while their dissociation may be a key parameter for extensive submarine slumping.

GeoHazards – Monitoring of geoprocesses

The Department of Marine Geology-Geophysics is working towards establishing and deploying Sea-Floor-Observatories through the implementation of research projects related to the study and long/short term monitoring of marine geological/geodynamic processes (chemical, physical, biological and geological).

Monitoring offshore seismicity: One of the main objectives is to provide systematic deployment of ocean-bottom-seismographs and their linking to the National Seismological Network. Along with that, short-term deployment of ocean-bottom seismographs is desired as a fast response after large seismic events, to monitor and study post-earthquake microseismic activity. A pressure sensor has already been mounted on the existing HCMR’s Deep Sea Observatory, deployed off SW Peloponnese, and operates experimentally aiming at the early detection of tsunamis.

Monitoring of offshore faults – submarine landslides: The objective is to develop and deploy at the seafloor observatories dedicated to the monitoring of active submarine faults and landslides for monitoring dislocations of the seafloor due to faulting or sliding, fluid flow through active faults, mud volcanoes and cold seeps, and pockmarks.

Anthropogenic activities

This action incorporates the study of the impact of any kind of anthropogenic activities on the natural processes, as well as the vulnerability and impacts of geological processes and hazards on the anthropogenic constructions and activities.

Anthropogenic impact: Coastal erosion and/or sediment deposition in ports occurs in many places along the Greek coastline and derives from unsuccessfully designed constructions at the coastal zone or other activities or along the river beds. Locating and mitigating the causes which disturb the coastal dynamics is amongst the main objectives and research activities alongside the contribution to coastal-friendly constructions and activities designs.

Submarine constructions and pipeline route surveys: The skills and the experience of its personnel along with the state-of-the-art scientific equipment allows the implementation of complex applied works and studies both in shallow and deep waters which are related to the construction of underwater works and deployment of pipelines and cables.

Managing marine accidents: The contribution to the discovery and location of modern wrecks (ships, crashed aeroplanes and helicopters) on the seafloor or in cases of leakages from submarine pipes has been of crucial importance.

Dredged material management: The Department has a long experience in all stages of planning, designing, and monitoring. The studies carried out incorporate ecological concepts and engineering designs with environmental, economic, and social feasibility for managing open-water / confined dredged material placement areas for both short- and long-term disposal needs.

Coastal erosion: In the context of an integrated approach for assessing and mitigating coastal erosion, GIS techniques and 2D numerical models for simulation of coastal processes are used. Morphodynamic models contribute to the interpretation of physical processes on coastal areas, providing a tool to researchers for assessing the effectiveness of various mitigation measures in order to protect such areas against erosion.

Underwater Geo-Archaeology

Underwater Geo-archaeology is multi- and interdisciplinary scientific discipline, bringing marine geoscientists and engineers together with archaeologists for the research on the submerged cultural heritage at full ocean depth. Underwater Geo-Archaeology includes Deep Water Geo-Archaeology (shipwrecks), Coastal Geo-Archaeology (shallow submerged antiquities, including shipwrecks) and Continental Shelf Prehistory Geo-Archaeology (submerged prehistoric landscapes and archaeology).

Since 2000, a long record is produced of Deep Water Geo-Archaeology surveys. The development of new methodologies for a more effective interpretation of the geophysical records, and the use of deep-water state-of-the-art technology including Thetis submersible, ROVs and AUVs, led to the discovery and detailed imaging of ancient shipwrecks in deep waters. More than 30 shipwrecks dating to various periods (classical, Hellenistic, Roman, Byzantine and post-byzantine) have been found and studied on the seafloor of the Aegean and Ionian Seas. Among the highlights are the discovery of Hellenistic shipwrecks at 70m depth between Chios and Oinousses Islands and at 500m west of Kythnos Island. The deepest ever-found ancient shipwrecks in the Mediterranean Sea are: two Roman shipwrecks at depths of 1200m and 1400m and a post-Byzantine shipwreck at 1300m depth in the Ionian Sea, west of Paxoi Islands. Moreover, coastal Geo-Archaeology surveys include detailed and systematic mapping and imaging of the submerged Late-Neolithic – Early Helladic Pavlopetri, reconstruction of paleo-coastlines and shallow submerged landscape of the Bay of Vatika and the area off Ancient Ramnous and other surveys.

Continental Shelf Prehistory Geo-Archaeology aims at reconstructing the submerged prehistoric landscape and discovering remains of the prehistoric cultural heritage on the seafloor. During the last glacial maximum some 20,000 years ago, an extensive sub-aerial landscape was exposed on the continental shelf down to at least 120 m, adding some 40% of new land to the total European landmass. This now-drowned landscape is known to preserve extensive records of palaeo-shorelines and other traces of the original landscape topography, fluvial and lacustrine sediments, and palaeo-environmental and archeological records of human activity.