Geochemistry

Stores of Heating Gas

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Science  18 Jul 2003:
Vol. 301, Issue 5631, pp. 279
DOI: 10.1126/science.301.5631.279a

Methane hydrates, in which methane gas is bound within and stabilizes a water-ice cage structure, are thought to be abundant in continental shelves and on or near the ocean floor. The breakdown of these clathrates would release large amounts of methane, an important greenhouse gas, and is thought to have been responsible for some of Earth's abrupt climate changes in the past.

Clay minerals contain a silicate layer and an interlayer typically of water or hydrogen, and are abundant in ocean sediments and areas of permafrost. Guggenheim and van Groos show that methane hydrate can be formed and trapped as a layer within the lattice of clay minerals. This new clay-hydrate phase is stable at pressures greater than 4 MPa (40 bars), as is the free methane hydrate, and its density is roughly equal to that of clay-rich sediments. The authors speculate that the low temperature-triggered dissociation of the clay-hydrate may serve as a buffering mechanism during periods of global cooling. — BH

Geology 31, 653 (2003).

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