Schematic depicting onshore to deepwater ocean basin

On this cross-section from onshore to deepwater ocean basin, gas hydrates occur in and beneath permafrost onshore and on continental shelves flooded over the past 15,000 years of sea level rise. For the deepwater system, the gas hydrate zone vanishes on upper continental slopes before thickening seaward in the shallow sediments with increasing water depth. On contemporary Earth, gas hydrates are most likely to be breaking down in Sectors 2 and 3.