Science: The real power of the deep

Beneath the waters of the area of ocean known as the Bermuda Triangle is an ancient, immensely powerful source of energy. But before anyone thinks the science section has suffered a bad attack of New Age nonsense, let's get things straight. The energy source is methane gas, and there are no alien spaceships or suburbs of Atlantis round here.

The myth of the Bermuda Triangle as the site of mysterious disappearances and strange events has generated millions of profitable words for the Aliens-Ate-My-Hamster school of writers, not least Charles Berlitz, whose book on the subject has sold nearly 20 million copies in 30 different languages since 1974. But for a better indication of the extent of the mystery, it's probably more reliable to look to the shipping insurers, who really care about the number of sinkings on the high seas. Lloyds' spokesman Norman Hooke has put the insurers' view of the Bermuda Triangle simply enough: "There are just as many losses as in other wide expanses of ocean," he says. Nor do the US Coastguards who patrol this supposed oceanic Twilight Zone see anything unusual going on, putting the blame for most sinkings not on aliens but on the more mundane perils of human incompetence, severe weather, treacherous currents and some of the deepest waters in the world. The oft-repeated claim that the waters round these parts are millpond smooth and shallow is mere fiction.

Of course, ships can disappear suddenly, oceans can boil and instruments can go haywire. But scientists now have an explanation for these phenomena, and the cause is chemical rather than extraterrestrial. It goes by the name methane gas hydrate, and though it doesn't have quite the same ring as Atlantis, it is strange stuff.

All gases except hydrogen, helium and neon are now known to be able to form compounds called hydrates in association with water if enough gas and water are present, the temperature is cold enough and the pressure high enough. Joseph Priestley, the British discoverer of oxygen, is believed to have produced oxygen hydrate sometime in the 1780s, while chlorine hydrate was produced by Sir Humphrey Davy in 1810. It was the discovery by Soviet workers of a strange "fizzing ice" blocking up their natural gas pipes in 1928 - and its identification six years later by the American chemist E G Hammerschmidt as a hydrate of methane - that began the trail leading towards the Bermuda Triangle.

Methane hydrate is methane that has been entombed inside an icy crystalline cage of water molecules, a chemical jail into which large amounts of gas have been squeezed by high pressure and cold. In the case of methane (the major constituent of the natural gas that makes your cooker go), one litre of the hydrate that had formed in the chilly gas pipes of Kazakhstan in the 1920s amounted to 167 litres of pongy gas and a puddle of water when it made its energetic expansion to normal atmospheric pressure after removal from the icy ground. One place where temperature and pressure conditions are right for methane hydrate to form is permafrost. Another, reasoned the experts, should be seafloor sediments in water several hundred metres deep, where pressure and temperature are also right for methane - created by decomposing organic debris - to wind up locked into the jailhouse of methane hydrate.

Experts found what they were after in the early 1970s when the fizzing ice that had caused consternation in Kazakhstan five decades before turned up again in test cores drilled through the ocean floor in (spooky this) the Bermuda Triangle. Around the same time, oceanographers realised that strange sonar readings of the seabed floor, which seemed to show a second phantom seafloor several hundred metres beneath the real one, were also an indication of gas hydrate layers. Global surveys have now found these signals (called the "bottom simulating reflector" or BSR) along continental sea slopes all over the world, a fact explaining less well-publicised tales of Bermuda Triangle-style weirdness from places as far apart as the Caspian Sea and Japan (anyone want to read my forthcoming get-rich-quick books on the mysteries of the "Caspian Square" or the "Japanese Pentagon" regions?) What the geographical spread of seafloor hydrate also represents is a huge storehouse of methane gas waiting to be freed from its prison cell and put to use.

But, as with any jailbreak, there are risks involved. With methane hydrate, an uncontrolled release is asking for trouble. In fact, gas-industry experts were already familiar with the dramatic effects of methane gas blowouts when ocean drilling went wrong, but it was not until 1981 that geochemist Richard McIver went public on a link with the Bermuda Triangle myth - a subject in which he had been interested ever since idly picking up one of the first bunkum articles on the subject in 1964 while waiting for a haircut in an Oklahoma barbershop.

There are many dangers in a methane gas blowout. One is its effect on water itself. To a ship at sea, water is a changeable medium, where buoyancy depends on density, which depends on things like salinity and temperature. For example, warm freshwater is less dense than cold saltwater, so a ship would float lower sailing up a warm river than out on the Atlantic. It was this fact that led Samuel Plimsoll in 1876 to devise the line that all ships now have on their hulls to indicate how far they can be loaded and still be safe if the density of the water beneath them changes.

So imagine what would happen if an ocean floor methane gas pocket was ruptured. A vast reservoir of gas would suddenly surge from the seabed, rising up in a giant plume through the ocean before erupting on the surface without warning. Even a tiny puncture in an undersea gas pocket can release vast amounts - a hole just one foot across in one North Sea blowout released over 30 million cubic metres of gas.

An airline pilot flying within view of (but for-tunately not directly over) just such a blowout off Puerto Rico describes seeing a giant section of ocean suddenly starting to boil, an area of chaos big enough, in his words, to drop New York's expansive Kennedy Airport into. The maelstrom lasted for three minutes before suddenly calming, leaving the sea looking normal. "It appeared from nothing, and reverted to nothing," said the pilot.

A ship caught in such a blowout would be doomed. The water beneath it would suddenly become much less dense due to the gas, sinking it in a matter of moments - the fate of over 40 rigs lost to gasified water worldwide. The vessel would plunge into the depths, where it would be covered up as sediment disturbed by the blowout settled back on the seabed. Another supernatural disappearance or just another natural disaster?

Planes, too, could fall prey to the deadly blowout. A plume of methane gas would continue to rise once it had reached the ocean surface since methane is lighter than air, and any aircraft flying into this invisible zone of danger would face two hazards. If the methane were very concentrated, its engines would fail through lack of oxygen. A more likely disaster, however, would result if the plume mixture was between 5 and 15 per cent methane. Such a mix is explosive and not the place you want to be with hot engine exhausts. Debris from the resulting explosion would also sink rapidly in the low-density, gasified water beneath it. No Mayday, no nothing, just a sudden disappearance off the radar screen.

McIver's theory can also explain reports of instrument malfunction but, again, no Atlantean forces need to be called upon, just the principles you find at work in a household ioniser. Agitated water generates negative ions, a fact that ioniser advertising plays on with references to babbling mountain brooks or waterfalls. A methane gas blowout, however, would not make you feel good. The massive surge of negative ions generated by its eruption on the surface would create a powerful magnetic field (electric charge and magnetism being inextricably linked), which could send compasses and other instruments haywire on any ship or plane in the vicinity.

McIver's theory, of course, depends on there being something to cause the gas blowouts, since the Bermuda Triangle isn't yet an area of heavy gas drilling. Nature, however, offers a solution in the shape of underwater landslides, and McIver's proof came from an unexpected source when he discovered that telephone companies had long suffered cable breakages all along the North American continental shelf. Sonar surveys have now shown that the vast majority of breakages occur at the site of seafloor landslides. Such slumps can be massive - one was 40 miles wide - and would easily rupture gas hydrate layers beneath the seafloor, freeing the gas trapped beneath the hydrate "cap" as well as liberating the massive amounts of methane trapped within the hydrate itself, which would break open as the pressure changed.

But a substance that is bad news for any ship or plane passing at the wrong moment also offers an amazing solution to the energy demands of the next century. Hydrates store immense amounts of methane, not counting the methane natural gas that exists in conventional form beneath the hydrate layers themselves. Remember, one helping of methane in its pressurised hydrate form is equivalent to 167 helpings of free methane. The US Geological Survey has estimated that just two relatively small areas off the North and South Carolina coast (part of the Bermuda Triangle) contain over 70 times the annual gas consumption of the US, while putting 16 noughts after a two gives you an idea of the current global estimate for cubic metres of methane gas locked in hydrates.

"The present oil-based economy may well be replaced by a natural gas- based one as early as the first or second decade of the next century," says Peter Miles of the Southampton Oceanography Centre. "Just 1 per cent of the most conservative estimate of gas hydrates is equivalent to half the current proven conventional gas reserves."

Methane gas hydrate, says Miles, is "the last remaining hydrocarbon" waiting to be exploited, and leading industrial nations are already setting up both ocean and permafrost drilling projects to do so. Russian experts expect up to 5 per cent of their total methane production to come from permafrost gas hydrate by 2000, while Japan plans a demonstration project of ocean hydrate harvesting in the Nankai Trough by 1999.

The news may not be all good, though. The fact that methane hydrates are only stable under narrow temperature and pressure conditions makes them especially vulnerable to climate change. Some experts believe that global warming - which is expected to be most pronounced in polar regions - could trigger the catastrophic decay of the shallow gas hydrates within the permafrost. Since methane is a greenhouse gas, this leads to more global warming, causing more hydrate decay, and the start of a nasty climatic cycle.

Its volatility means that the number of people who have actually seen methane gas hydrate in its fizzing state is tiny. Yet its presence is likely to loom over the early decades of the next century, a powerful force that may give us energy to burn - or burn us up instead. !