Storegga

Storegga
Name	Storegga
Settlement type	Submarine landslide complex
Country	Norway
Region	North Sea

Storegga is a submarine landslide complex off the coast of Norway on the continental shelf of the North Sea near the Shetland Islands and Orkney Islands. The area is notable for episodic large-scale submarine mass movements that produced palaeotsunamis affecting coasts of Scotland, Norway, Faroe Islands, and Greenland. Research into the site intersects studies by institutions such as the British Geological Survey, University of Bergen, University of Edinburgh, National Oceanography Centre (UK), and the Norwegian Geological Survey.

Geological setting

The complex sits on the continental margin adjacent to the Norwegian Trench and the passive margin formed after the Caledonian orogeny and the opening of the North Atlantic Ocean. Seabed stratigraphy records Quaternary glacio-eustatic cycles driven by the Weichselian glaciation and modulated by sediment supply from palaeo-rivers like the River Thames (historic) and glacial outwash from the British–Irish Ice Sheet and the Scandinavian Ice Sheet. Tectonic inheritance from the Caledonian orogeny and thermal subsidence associated with the opening of the North Atlantic Ocean influenced shelf architecture, slope gradients, and depocentres such as the Vøring Basin and Shetland Platform. Benthic sedimentation includes glacial till, turbidite sequences correlated with cores held by the National Oceanography Centre (UK) and seismic records archived by the British Geological Survey.

Storegga Slides

The complex comprises multiple large-scale slide scars identified in seismic reflection surveys by teams from the Geological Survey of Norway and the University of Bergen and logged in piston cores recovered by research vessels such as RRS James Cook and RV G.O. Sars. The best-known event is a Late Holocene slide mapped across the continental slope between the Shetland Islands and the Norwegian coast, with runout deposits extending into the Muckle Flugga region and the Faroe–Shetland Channel. Geological mapping links the slide deposits to distal turbidite fans in basins like the Vøring Basin and the Faroe–Shetland Basin. Structural interpretation uses datasets from the European Marine Observation and Data Network and palaeoseismic studies comparing features seen near the Storegga scars with those at other submarine landslide sites such as the Grand Banks and Northeast Atlantic margins.

Tsunami generation and impacts

Large-scale sediment failures produced tsunamis modelled by teams at the University of Bergen, University of St Andrews, and the National Oceanography Centre (UK)],] with numerical simulations using bathymetry from the General Bathymetric Chart of the Oceans and run-up data from coastal stratigraphy on Shetland, Orkney, Scottish Highlands, Norway, and the Faroe Islands. Geological evidence for inundation includes buried peat sequences in the Morar area, storm-surge deposits correlated with radiocarbon ages from the University of Aberdeen and palaeoecological shifts recorded at sites studied by the Royal Society of Edinburgh. Modelled tsunami heights varied across the North Sea, producing run-up estimates that influenced interpretations of contemporaneous coastal abandonment seen in archaeological sequences at Orkney, Shetland, and along the Norwegian coast.

Chronology and dating

The principal Late Holocene slide is dated to the early Holocene using radiocarbon dating of organic material from coastal peat and marine shells calibrated against INTIMATE chronologies maintained by the University of Cambridge and laboratories such as the Norwegian University of Science and Technology and the Scottish Universities Environmental Research Centre. Ages cluster around c. 8,200–8,100 years BP in widely cited datasets, which link the event temporally to climatic episodes recorded in ice cores from Greenland and palaeoclimate proxies assembled by the PAGES community. Stratigraphic correlation employs tephrochronology using distal ash layers traced to eruptions catalogued by the International Volcanic Health Hazard Network and regional isochrons developed by the Quaternary Research Association.

Causes and mechanisms

Investigations attribute failure to combinations of rapid sediment loading from meltwater discharge associated with collapse of parts of the British–Irish Ice Sheet and destabilisation by gas hydrate dissociation under pressure–temperature changes documented in models from the GEOMAR Helmholtz Centre for Ocean Research Kiel. Triggering mechanisms considered include earthquake shaking linked to glacioisostatic adjustment events recorded in relative sea-level records by the British Geological Survey and postglacial seismicity spectra compared with datasets from the International Seismological Centre. Laboratory experiments and numerical models developed at the Massachusetts Institute of Technology and the Delft University of Technology examine liquefaction, pore-pressure diffusion, and retrogressive failure processes consistent with observed headscarp geometries.

Human and environmental consequences

The tsunami and associated sediment redistributions had implications for Mesolithic communities documented archaeologically at sites like Orkney's Broch sites and coastal habitation layers analysed by teams from the University of Aberdeen and University of York. Palaeoecological impacts include abrupt changes in pollen and diatom assemblages recorded by the British Trust for Ornithology and palaeobotanical studies at the Royal Botanic Garden Edinburgh that indicate saltwater inundation of coastal peatlands. Long-term geological consequences shaped the North Sea seabed, influencing later hydrocarbon exploration strategies by companies collaborating with the Norwegian Petroleum Directorate and guiding modern tsunami hazard assessments undertaken by the Norwegian Water Resources and Energy Directorate and the UK Met Office.

Category:Submarine landslides Category:Holocene geology Category:Geology of Norway