“Combustible ice”, also known as Methane Hydrate, is a naturally occuring substance that lies in depressions and in layers sometimes hundreds of feet thick on the ocean bed. At great depths, say in excess of 1,000 meters or more, the combination of pressure and the steady low temperature (about 4 degrees Centigrade), cause water and methane to form a substance, in which the small, symmetrical molecules of methane are trapped in the interstices of the larger and polarized molecules of water. Something like 165 volumes of methane combine with one volume of water.
So long as the Methane Hydrate is kept at below about 6 degrees Centigrade, it is stable, but above that temperature, it undergoes a phase change, releasing the methane (natural gas), which expands back to its original volume, with potentially serious destructive effect on the machinery being employed to extract it.
It is estimated, that something like four to ten times as much chemical energy is contained in the quantities of Methane Hydrate frozen in the polar regions, and the deposits on the ocean floor everywhere, as ALL the known or suspected reserves of coal, petroleum or natural gas in rock strata throughout the entire world. If we could tap into even a small fraction of this store of methane, it would serve the needs of the world for centuries, so much so that photovoltaic panels or arrays of wind-driven turbines become what they have always been, a curiosity which will never provide more than a small fraction of one percent of the total energy extraction industry.
And surprise, surprise, the Chinese may develop the technology first, as we blindly scramble around trying to make “green energy” work. Not our best application of resources.
Maritime stories of ships sinking in a boiling sea may in fact be due to a large cloud of methane hydrate roiling up beneath a vessel, changing the specific gravity of the media in which the hapless ship is caught. I have often wondered if an electromagnetic field could be generated by a large ‘bubble of methane rising through sea water, thus disturbing the compasses of planes fying at lower altitudes. Perhaps that is what confused the flight of WWII planes lost off the eastern seaboard?