Norsk Geologisk Forening
Oslo-avdelingen
Torsdag 15. november 2007
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15. november: "Sampling gas hydrates: insights from new discoveries on the Norwegian margin" v/Adriano Mazzini (PGP, UiO).
Gas hydrates along continental margins and the significance of clathrates in the Vøring-Storegga region (Norwegian Sea): sampling and sea floor observations A. Mazzini (1) Physics of Geological Processes, University of Oslo, Box 1048, 0364 Oslo, Norway Methane hydrate is a clathrate, an ice-like solid formed from methane and water, that is stable under conditions of pressure and temperature found in most of the world's oceans at depths greater than a few hundred meters. Hydrate occurs beneath the seabed where there is sufficient methane to exceed its solubility in water within the hydrate stability field. They are broadly distributed in active and passive continental margins and particularly in the cold Arctic regions, in the Gulf of Mexico, in the Black Sea, Sea of Japan Sea of Okhotsk and, more recently, west African margin. Gas hydrates have been broadly studied in these regions both for the potential hazard that their dissociation would pose and for the possibility to exploit the methane entrapped. It has been speculated that methane released from hydrate by climate-induced changes in pressure and temperature escapes into the ocean and into the atmosphere, where its acts as a greenhouse gas. Further, methane from beneath the seabed is the primary energy source for communities of chemosynthetic biota at the seabed. Impressive gas hydrate deposits have been recently discovered during the TTR15 cruise (2005) in the Georgian margin where stratified and blocky gas hydrates coexist with oil deposits. More recently during the TTR16 Cruise (2006) in the Nyegga region, Norwegian Sea, six large pockmark and mound features were explored with TV remote controlled grab and gravity corer devices. This discovery represents a significant achievement as gas hydrates in the Norwegian Margin have been suggested by numerous scientists but never been proved by sampling. The combined studies of the recovered gas hydrates, and the authigenic carbonates that characterize seepage sites, reveal important insights about the past and present plumbing system at pockmarks. Last ned plakat (1.8 MB JPG) Oppdatert 7/11-2007 Institutt for geofag, Blindern. Tidspunkt: kl. 19:00 Enkel
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