Clathrate hydrates

Substantial volumes of methane gas are trapped below the seafloor and in pe rmafrost by an ice-like solid called clathrate hydrate. Global estimates of the methane in clathrate hydrate may exceed 10(16) kg, which represents on e of the largest sources of hydrocarbon on Earth. Speculations about large releases of methane from clathrate hydrate have raised serious but unresolv ed questions about its possible role in climate change. Progress in our und erstanding of clathrate hydrate has been made through integrated geophysica l and geochemical surveys of known clathrate occurrences. Details from thes e surveys have motivated new investigations of the physical, chemical, and biological processes that contribute to growth and breakdown of clathrate h ydrate in natural settings. In this article, I give an overview of recent a dvances and future challenges.