Billions of dollars are invested yearly for the purpose of space exploration, as navigating the galaxy is almost an obsessive preoccupation for the human race. Yet very little is known about the vast majority of our own planet: the internal mass of the Earth is immense yet, for the most part, the contents of inner Earth still remain a mystery with relatively little known of the secrets that lie beneath its surface and deep into its core.
The scientific community is in general agreement that the world below us consists of four layers: a rocky outer crust, a mantle of hot viscous rock, and a dual layered core. The molten outer core creates the Earth's magnetic field in conjunction with the solid, spinning, stupendously hot inner core where temperatures are now thought to reach more than 6000C (10832 degrees Fahrenheit), as hot as the sun.
The inner core is believed to act like an electrical motor, creating electrical currents in the outer core which in turn create the Earth's magnetic field. Variations in temperature, pressure and composition within the liquid core generate convection currents as cool matter sinks and warm matter rises. The spin of the Earth creates the Coriolis force, producing eddies in the molten rock which in turn generate electric currents.
As scientists have not yet been able to journey to the centre of the earth to verify these facts, there is still speculation as to whether the internal composition of the planet is actually constructed in this way, but all of the available evidence appears to substantiate this theory. Otherwise, the immense area within the earth remains uncharted territory.
The possibilities of underground worlds existing deep in the bowels of the planet have intrigued and inspired authors such as Jules Verne, J.R.R. Tolkien, and Edgar Rice Burroughs. The concept is even incorporated into some of the world's religions, particularly Buddhism. Buddhists believe in a flourishing subterranean world known as "Agharta," an advanced civilisation possessing a plethora of cities serving millions of inhabitants. The capital city is known as "Shamballa" and it is thought throughout the Orient that the Supreme Ruler of the Empire, also known as "The King of the World," resides there. The Dalai Lama of Tibet is considered to be the King's terrestrial representative, receiving messages transmitted to the surface through secret tunnels connecting the subterranean world with Tibet.
There is no solid evidence to support this idea, of course, though the concept of a subterranean world is present in most cultures throughout the world.
In his book, "Journey to the Centre of the Earth", French science-fiction author Jules Verne envisaged that an enormous ocean was contained deep under the surface of the planet. This seems like a very unlikely concept, yet according to a recent scientific study, Verne's vision may not be too far away from the truth.
The discovery of a rare mineral has now pointed to the existence of an enormous underground body of water held in the mantle layer of the inner planet, scientists have revealed in an article published in the journal Nature. Evidence suggests that the reservoir is located approximately 400-600km (250-375 miles) under the Earth's surface and is potentially so vast that it could contain as much water as all of the surface water on the planet combined.
This amazing fact has been deduced solely from the presence of a hydrophilic mineral known as ringwoodite, which is believed to have emerged from the transition zone between the upper and lower layers of the Earth's mantle. Ringwoodite was named after the Australian geologist Ted Ringwood, who hypothesised that a special mineral was bound to be created in the transition zone because of the ultra-high pressures and temperatures there.
The discovery of the water-rich mineral, which is composed of up to 1.5 per cent liquid, substantiates previously contested theories that the transition zone contained water, opposing alternate views which believed the zone was dry.
"This sample really provides extremely strong confirmation that there are local wet spots deep in the Earth in this area," said study leader, Graham Pearson of Canada's University of Alberta. "That particular zone in the Earth, the transition zone, might have as much water as all the world's oceans put together."
Ringwoodite has only previously been found in meteorites, as geologists had never been able to descend far enough into the Earth's inner areas to retrieve any samples from our own planet. The find was pure luck: back in 2008, a team of amateur gem-hunters were trawling a shallow river in the Juina area of Mato Grasso, Brazil , when they happened upon a tiny, grubby stone called a brown diamond. The stone ended up in the hands of a group of scientists who were actually searching for other minerals.
In its interior, a tiny piece of ringwoodite was discovered which measured just 3mm (0.12), the first terrestrial sample ever to be acquired.
"It's so small, this inclusion, it's extremely difficult to find, never mind work on," Pearson said in a press release, paying tribute to the diligent work of grad student John McNeill."It was a bit of a piece of luck, this discovery, as are many scientific discoveries."
Researchers hypothesise that the worthless brown diamond hitchhiked to the surface in a torrent of kimberlite, the deepest known form of volcanic rock.
The find was not immediately recognised as ringwoodite, and it has taken years of scrutiny in specialised labs using spectroscopy and X-ray diffraction to authenticate the find.
The implications of the discovery could be profound, according to study leader Pearson, though Hans Keppler, a geologist at the University of Bayreuth in Germany, was more conservative in his response. He is uncertain whether such a small sample can provide an accurate indication of the amount of water likely to be located in the transition zone, and he was keen to dispel any notions relating to underground oceans of the type visualized by Jules Verne.
"In some ways it is an ocean in Earth's interior, as visualised by Jules Verne... although not in the form of liquid water," Keppler said in a commentary also published by Nature.
The water is likely to be contained in rock, rather than being present as a large, free-flowing body of water, but whatever form it takes, if large volumes of water are indeed existing beneath our feet, there is the potential for it to affect the movement of tectonic plates and the eruptions of volcanoes.
"One of the reasons the Earth is such a dynamic planet is the presence of some water in its interior. Water changes everything about the way a planet works," said Pearson.
A separate study, conducted recently by scientists at the University of Liverpool, England, has indicated that immense quantities of water could be flowing through the mantle layer through fissures in deep sea seismic fault zones.
"It has been known for a long time that subducting plates carry oceanic water to the mantle," said Tom Garth, a doctoral student in the school's Earthquake Seismology research group. "This water causes melting in the mantle, which leads to arc releasing some of the water back into the atmosphere. Part of the subducted water however is carried deeper into the mantle and may be stored there."
Evidence presented in the paper, which was published in the journal Geology, suggests that based on the age of the earth, the subduction zone off the coast of Japan could have allowed as much as three-and-a-half times the total volume of all the surface oceans combined to leak down into the mantle.
Garth stated that the researchers "found that fault zones that form in the deep oceanic trench offshore Northern Japan persist to depths of up to 150 km. These hydrated fault zones can carry large amounts of water, suggesting that subduction zones carry much more water from the ocean down to the mantle than has previously been suggested."
It is believed that the collected water causes the mantle material to melt and causing volcanoes above the subduction zone, like those that form the "Pacific Ring of Fire."
Water that does not interact with the molten rock seeps deeper into the mantle, where it has accumulated.
Scientists using seismic models have analyzed earthquakes occurring deep inside the earth in the seismically-active Wadati-Benioff zone that can span up to 670 kilometers, or over 400 miles, below the area where one oceanic plate sinks under another plate and heads deep into the mantle. Seismic waves in the researched area had low velocities and occurred along 1-2km wide fault zones, which indicated that the waves were traveling through the mineral content of the mantle combined with water. It appears that the hydrated fault zones can carry large amounts of water, some of which is retained in the mantle, while some is released when tectonic plates heat up.
These studies present science with a wealth of new material regarding the composition of inner earth and the potential impact of underground water sources on the surface. The presence of an underground water source could also add further weight to the theory of subterranean civilisations, as access to water increases the possibility that societies could potentially survive deep inside the earth. One wonders what secrets the Earth still has to yield, and every discovery made by science could bring us a step closer to understanding not only the complex and wonderful planet that we live on, but also the basis of some of its longest-standing legends.
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