Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Reconnaissance mapping of a giant deep sea vent in the Sea of Okhotsk

The research project focuses on a physical and chemical process which occurs on the deep sea floor and is controlled by the forces of plate tectonics. It has been discovered only in the recent past that sediments at convergent plate margins are tectonically deformed and compacted This results in tectonic dewatering, such as the effusion of large amounts of hot pore fluids along diffuse and discrete pathways through the sedimentary column Saturated with methane and other chemical components, fluids emerge at the sea floor where they may form large vent fields. This reflux of methane-rich fluids to the ocean-atmosphere system has not been adequately accounted for in models of the global methane cycle and may be a sizeable component in numerical models of the global budget of greenhouse gases.

The mapping of vent fields on the western slope off Paramushir Island, in the northern part of the Kuril Island arc system south of Kamchatka was a major task. In this area an eruption flare of methane-rich fluids extending up to 500 m above the sea-floor marks the site of active venting. During the expedition three individual areas were studied in detail by seismic mapping, geochemical and sedimentological sampling. Despite considerable technical and logistical problems the expedition successfully surveyed a large area off the islands Paramushir and Onekotan. West of Paramushir the venting of methane rich fluids is controlled by the presence of gas hydrates which are visible as a bottom simulating reflector in seismic images and the change of pressure/temperature conditions due to recent volcanic intrusions, which act as a heat source, to break down these hydrates and less importantly by regional tectonic movements related to plate boundary processes as well as local processes related to volcanism.

Reported by

Christian-Albrechts- Universität zu Kiel
Wischhofstraße 1-3
24148 Kiel
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