Assessing methane release from submarine landslide

Undersea landslides may play a role in releasing the potent greenhouse gas methane into the ocean and atmosphere.

Yet new evidence suggests that a huge, ancient, submarine landslide belched little if any methane. Paull et al. studied the 8,000-year-old Storegga Slide, the largest known of many landslide scars within continental margins. Located off Norway, the Storegga Slide is believed to have occurred in sediments that may have initially contained gas hydrates. Those ice-like solids composed of water and gases, such as methane, form under low-temperature, high-pressure conditions and are common within continental margins. Using analyses of sulfate concentrations to model the relative amounts of methane present in sediments within and around the landslide, the authors find that considerable methane exists in sediments adjacent to and unaffected by the Storegga Slide. However, methane was absent from sampled landslide debris and from sediments exposed by the slide. The authors hypothesize that either methane was lost during slope failures prior to the Storegga Slide event, or that it was never present in significant concentrations within the sediments that failed.-American Geophysical Union