Sunday, Nov. 22, 2009

On a plate: A map of the world showing the boundaries of the 15 largest tectonic plates on the surface of the planet as delineated by Plate Tectonics Theory. The theory assumes the planet has always been about its present size, and that many of its landforms have been created as a result of enormous pressures caused by movements of these plates. U.S. GEOLOGICAL SURVEY

By JEFF OGRISSEG

Special to The Japan Times

The competing claims of Growing Earth Theory and Plate Tectonics Theory as presented in the accompanying article may appear to be a recent rivalry, but they are in fact following in a long tradition.

Soon after accurate maps of the world were first drawn courtesy of the great European navigations of the 15th to 18th centuries, scholars studying them were struck especially by the facing coastlines of Africa and North and South America that appeared to fit into each other if pushed together.

Consequently, they theorized that those continents — and by extension other land masses — were long ago much closer together. Just how long ago, however, was not determined until well into the 20th century.

Back in 1912, a German scientist named Alfred Wegener (1880-1930) published his theory of continental drift, which he believed held the key to answering those questions.

According to this, the land masses were once one giant continent Wegener named Pangaea that was surrounded by water, and they arrived at their present positions by drifting around somewhat like melting ice cubes do on a sheet of glass.

Most of Wegener's evidence was circumstantial and his theory failed to explain the geological mechanism driving continental drift — how, for example, the Indian shield, ancient rock that is essentially welded to the mantle, could break loose and ram northward into Asia and keep on going with such force as to cause the giant ripples now known as the Himalayas.

Wegener's hypothesis was largely forgotten until the 1950s, when it was dusted off and revised to become Plate Tectonics Theory a decade or so later. And that — despite being so complex in its supposed workings and requiring such radical geomorphic change over a very short period of geological time as to render the Earth unique in the whole of our solar system as we know it — became the received wisdom now generally treated as fact. Interestingly, though, it's not so long since science was leaning in favor of a far simpler explanation that followed in the footsteps of those who had centuries before set their eyes on the first world maps.

Scientists such as Otto Hilgenberg (1896-1976) in Germany and Samuel Warren Carey (1911-2002) in Australia, working in the years before World War II, not only noted how the continents bordering the Atlantic appeared to fit into each other if pushed together. They also observed, and made models to show, that the Pacific, Indian and Southern Ocean continents also fitted together — but as one mass entirely covering an Earth half its present size.

Rather than accept this staggering proposition, though, scientists — without being able to refute it — instead latched on to the more comfortable alternative of Plate Tectonics Theory that didn't require any change in Earth's size.

However, that scientific consensus occurred despite oceanic surveys and deep-core sampling in the 1960s that began to plot a 65,000-km-long network of undersea volcanic ridges that run like the seams on a baseball around our planet — and which were found to be in constant and various stages of "eruption."

Advanced radiometric age-dating then revealed something truly remarkable — that the age of the oceans' floors increases symmetrically on both sides as you move away from the volcanic ridges. And yet more stunning, the findings also showed the ocean floors are nowhere more than 180 million years old.

From the results of this research it was a short step for some scientists to postulate a process of seafloor spreading. This holds that new volcanic material erupting from the submarine ridges is constantly forming new oceanic crust which, with the help of gravity, pushes the older crust further away. It was an analysis that seemed to quite adequately explain what enlarged the Atlantic and pushed the Americas and Africa apart.

But if this spreading has been happening over geological time from all the ridges, wouldn't that mean the whole planet must be growing in size?

Not necessarily said all those wedded to Plate Tectonics Theory.

In their collective mind, it was — and remains — more feasible that the surface of the planet is made up of crustal plates that are either converging, diverging or colliding with one another, all driven by heat from inside the planet.

In essence, such thinking is an extension of 1929's Theory of Continental Drift championed in the face of widespread skepticism by the English geologist and pioneer of radiometric dating, Arthur Holmes (1890-1965). According to Holmes, it is so-called convection cells in the mantle that dissipate radioactive heat from beneath, which then propels the continents around.

So both the continental drift and plate tectonics theories allow Earth's size to have remained relatively unchanged since its creation.

As far-fetched as the proposed mechanisms behind both these theories may have seemed to some, they gained a new lease of life through the work of seismologists Kiyoo Wadati (1902-95) at the Japan Meteorological Agency and Hugo Benioff (1899-1968) at the California Institute of Technology.

After conducting research independently in the 1930s on deep seismic activity, they theorized the existence of what came to be known as Wadati-Benioff Zones. In these zones, they maintained that tectonic instability appeared to be the result of one piece of crust being pushed — or "subducted," as they termed it — under another.

Armed with this new perspective, advocates of both continental drift and plate tectonics theories could now explain the relatively young age of the crusts forming oceanic floors as being the result of subduction.

From there it was but a short step to hypothesize that older basaltic crust underlying the oceans was either being swallowed by oceanic trenches or pushed beneath another plate, Wadati-Benioff style — and then "recycled" back through the magma to the oceanic rifts in a fashion resembling a conveyor belt.

But to cover all the bases in cases where neither of the above are happening, Plate Tectonics Theory allows for denser but thinner oceanic crust 8 km to 10 km thick to somehow be part of the same plate as the ancient, granite continental land masses up to 100 km thick. And, on some of the theory's delineated borders, such as that between the African and Eurasian plates, it's even OK for no tectonic markings to appear at all.

In short, it does seem the theory appears to make exceptions to fit each situation.

Back in Australia, meanwhile, Carey had initially supported the Theory of Continental Drift and set out to prove it. But his search for answers only led to more questions. Finally, inspired by Hilgenberg's work in Germany, and a growing list of similarities found in geological structures now separated by oceans, he eventually became a foremost advocate of Growing Earth Theory.

But Carey was far from alone in his scientific stance. Among his contemporaries was East German engineer Klaus Vogel, who in 1977 recreated a smaller pancontinental globe without oceans inside a transparent globe of the Earth as it now is, and Dr. Ken Perry of Wyoming, whose computer models corroborated expansion tectonics with geometrical precision. Carey's downfall, though, was that — like Wegener in the early 20th century — he was not a physicist and so could not propose a mechanism that might cause what the geological record was telling him had happened. Then when subduction reared its head, Earth no longer had a need to be growing.

In late 1993, Carey symbolically handed off the baton in a letter to Australian geologist James Maxlow, whose draft manuscript on Growing Earth Theory, Carey said, "would satisfy the most hostile examiner."

That hasn't exactly been the case, but Maxlow has remained an active force, disseminating research findings and various compelling evidence through books, papers and seminars in the face of continuing disdain — based on precious little scientific evidence — from mainstream scientists.

Undeterred, Maxlow continues to maintain that the difference between Growing Earth Theory and Plate Tectonics Theory simply boils down to whether or not the presumed need for a constant Earth-radius premise is true or false.

"The problem that mainstream geology imagines is that expansion tectonics is a threat to their career, research programs, reputation, or at the very least a threat to their intelligence," said Maxlow by e-mail.

"An expanding Earth is perceived by mainstream literature as having been proven wrong, so why should they bother."

Whether that's entirely the case or not, what certainly seems to be true is that rather than being pursued by the entire scientific community in a dedicated spirit of inquiry, research into how the Earth came to be the way it is now is tainted instead by dedications to dogma, whatever the exciting results of new research.

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