The Great Islands Under The Sea

THE GREAT ISLANDS UNDER THE SEA                                                                     continued



Wegener, a casualty of his own scientific research operations, died on an
icecap in Greenland, in 1930 and so did not live to see his theory of drift-
ing continents incorporated into a more extensive one.

The theory of moving tectonic plates, originated by Dr. Jason Morgan in
1968, describes more fully the motions of the separate sections of the
Earth's crust. 

This generally accepted theory suggests that the crust of the Earth is divid-
ed between ten to twenty major tectonic plates with subdivisons, and that
these plates and platelets cover all of the Earth's surface, dry land and
beneath the sea.

When the great plates, floating on the Earth's viscous mantle, grinding against
each other on their plate boundaries or fault lines (e.g. the San Andreas Fault,
an unwelcome reminder of doom to Californians), there occur earthquakes and
volcanic explosions, often of catastrophiac dimensions. 

The crux of the tectonic-plate theory is that the movement of the plates is not
only horizontal, but also verticaL, meaning that one plate can be pushed under
another and, in the case of the oceanic plates, fed into the fiery interior mantle
of the Earth, to eventually be spewed out again as lava from volcanic eruptions.

The islands of Japan, among others, were formed by such a volcanic buildup and,
like California, face the possibility of future subsidence.