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Microbial methanogenesis at continental margins produces concentrated gas hydrate deposits in coarse-grained sediments.

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Friday, October 02, 2015
12:00 pm - 1:00 pm
Dr. Alberto Malinverno
Earth & Ocean Sciences Seminar Series

http://www.ldeo.columbia.edu/~albertoIn the last few decades vast natural deposits of gas hydrate, a solid ice-like compound of water and methane, have been discovered in the sediments of the world continental margins. These deposits accumulate where methane is abundant, pressure is high, and temperature is low. Gas hydrates can dissociate when temperatures rise, releasing large amounts of greenhouse gases to the ocean-atmosphere system, and can amplify a warming trend. Gas hydrate dissociation may have played a key role in past climate perturbations, could be relevant for future climate change, and has the potential to trigger large submarine landslides. Finally, gas hydrates are being actively investigated as a possible energy resource. This talk will review studies on the formation of concentrated gas hydrate deposits in coarse-grained sediments. Gas hydrate formation is inhibited in the small pores of fine-grained sediments, where microbial methane is generated, but methane transported by diffusion can form gas hydrate in adjacent coarse-grained layers. This ¿short-range migration¿ has been shown to be quantitatively feasible in several sites drilled in the Pacific Ocean, Indian Ocean, and Gulf of Mexico. Short-range migration is likely a widespread mechanism for gas hydrate formation, as it requires only small amounts of organic carbon available for methanogenesis and sequences dominated by fine-grained sediments with a small fraction of coarse-grained beds.

Type: LECTURE/TALK
Contact: Beatriz Martin