ON THE GEOMORPHOLOGICAL EFFECTS OF GAS HYDRATES

There is increasing research into marine gas hydrates as a future clean-energy source. Although the total amount of gas hydrates in oceanic sediments may be huge, their local, in situ concentrations, and their exploitation potentials, presently, seem to be small. However, geomorphological structures found in the eastern Pacific, on both sides of the Atlantic Ocean, and in the Barents Sea, suggest that gas hydrates play a significant role in destablizing and redistributing marine sediments.

Examples of fluid flow, seabed instability, and blowout structures, suspected to be associated with marine gas hydrates will be discussed. A review of evidence from Hydrate Ridge, off Oregon (spring sapping, and vents); The Blake Plateau, off Carolina (mud diapirs, slides and seabed collapse structure); the Outer Niger Delta, off Nigeria (mud volcanoes and pockmarks); the Storegga Slide Complex, off Norway (spring sapping, fluid seep, and slide features), and the Central Barents Sea (blowout craters), will be presented and discussed.

There is also some geomorphological evidence of extraterrestrial sediment disruption by gas hydrates and/or ice. On Mars, there are clustered craters that may be caused by endogenic processes (i.e., destabilization of near-surface hydrates); and recently, spring sapping features have been found, which are probably caused by the destabilization of buried gas hydrate layers or frozen water. On comets passing the Earth, other features have been found (gas jets, pitting, and cratering), suggesting the dissociation of gas hydrates. Thus, gas hydrates may play a significant role in modifying topography both on Earth and near-Earth bodies.