Activities by coastal States in relation to the exploration and exploitation of non-living natural resources (namely hydrocarbons and deep-sea minerals) on the continental shelf beyond 200 nautical miles (M) from their territorial sea baselines are reviewed. Geological conditions dictate such that hydrocarbons are likely to occur where there are thick accumulations of sediments (at least 2-3 km is needed for organic matter to generate significant amounts of hydrocarbons), whereas deep-sea minerals are found on or beneath the seabed of the deep oceans, which are generally “starved” of sediment. Thus, in general, sites for hydrocarbon exploration and for deep-sea mineral exploration are unlikely to overlap. On a ‘normal’ geological shelf with an average width of say ~60-100 km, hydrocarbon exploration is carried out generally within the 200 M limit of the Exclusive Economic Zone (EEZ) of the coastal State. Within the last decade, however, necessitated by depleting resources in the shallow waters of the shelf and slope, exploration has gradually moved from the geological shelf (water depth typically < 200 m) further out into deeper waters, and in some cases, beyond the 200 M limit. Thus far, only in a few places is oil and gas exploration being carried out on the continental shelf beyond 200 M. Examples include Australia, New Zealand, Norway, Argentina and Canada. Such activities mainly involve geological and geophysical investigations and assessment of the hydrocarbon potential, while some have resulted in commercial production. Besides the conventional hydrocarbons (oil and gas), continental margin sediments may also host significant accumulations of gas hydrates, which are regarded as a potentially important energy resource of the future. Along non-polar continental margins, gas hydrates are generally found beneath the continental slope and the continental rise, i.e. beyond the continental shelf proper, in water depths typically greater than 500 m but still mainly within 200 M of the territorial sea baselines. Where the continental margin is exceptionally wide, however, gas hydrates may occur in areas beyond the 200 M limit, on the extended continental shelf.
Light δ13C events during deglaciation of the East Greenland Continental Shelf attributed to methane release from gas hydrates
