Further evidence of expansion is provided by the +65.3 mm/yr rate of increasing width in the trans-Pacific distance between Yaragadee, Australia, and Arequipa, Peru, measured by Smith, et al . This study, and others like it, was published as evidence of subduction, but the addition of width contradicts the principle of Pacific basin width reduction required by subduction on a fixed-diameter Earth; e.g., any increase in width is an increase in surface area of the Pacific basin and Earth's total surface area, circumference, and diameter-- with or without subduction.
The excellent evidence presented by Nakanishi, et al, is also very revealing. It shows a growth pattern based on isochron ages suggesting the Pacific Ocean seafloor started as a very small area near the Mariana Trench ~195 Ma when the trench was still close to North America. As the trench moved westward (relative to North America), new seafloor filled in behind it to form the northern Pacific basin. An areal increase of such magnitude in the past ~195 Ma is evidence of growth of the Pacific plate in the very area where subduction is supposed to be taking place. This is consistent with other evidence showing that Australia was conjoined with South America ~200 Ma. This Early Jurassic sediment in both the northern and southern basins of the Pacific Ocean constrains the age of the Pacific basin, and suggests the Pacific Ocean has only existed, at most, since the end of the Triassic (~200-205 Ma.)
This westward growth of the northern Pacific plate, starting from North America, where the sediments are youngest, provides an explanation for the unilateral growth pattern of the northern Pacific basin seafloor that distinguishes it from the bi-lateral growth patterns of midocean ridges currently found in the southern Pacific, Atlantic, and Indian Ocean basins. The pattern of decreasing sediment ages is what one would expect as new magma filled the void created by planetary expansion driving the continents apart.
Some major questions are raised by the findings of Nakanishi, et al, relative to the unilateral growth pattern of the North Pacific basin. Did creation of the Pacific basin begin in the northern hemisphere, or simultaneously in the northern and southern hemispheres? Was the breakup of Pangaea a sudden event caused by a catastrophic asteroid impact, or just a series of small, but steady, fractures in Earth's crust such as we see in today's major earthquake-prone areas such as the San Andreas Fault, the Northern Anatolian Fault (Turkey), and the East African Rift Valley?
A related question concerning the breakup of Pangaea is whether Australia and Africa broke away from South America simultaneously, or whether Australia was first, followed by Africa. Disparity in distances traveled (~10,000 km for Australia, vs ~4,000 km for Africa), together with differing ODP sediment ages, argue that opening of the Pacific commenced before the Atlantic Ocean began to form, but this may be simply a reflection of different growth rates in the two midocean ridges over the same period. Alternatively, did breakup of the continents to form today's ocean basins begin in the Indian Ocean area?
Expansion is evident also in the oblate figure of the Earth. Approximately 75% of all midocean ridges (which are really extended linear underwater volcanoes or LUVs) lie in the southern hemisphere, where most seafloor growth occurs. This continuing unequal growth in the southern hemisphere should be recognized as the cause of the oblate, or pear-shaped, figure of the Earth. Gravitational demands for spherical stability may in the future result in greater growth somewhere in the northern hemisphere that would restore the planet to a more spherical shape, but this is only a possibility that should be kept in mind.
In the southern hemisphere, Antarctica, completely surrounded by LUVs, continues to increase in circumference and total surface area without any hint of subduction --another insurmountable problem for subductionists. Antarctica, the Earth’s largest continent with 21.5% (36,260,000 km²) of the Earth's total surface area, also exemplifies the way continents are affected by expansion--they expand radially outward from Earth's center, as well as laterally relative to other continents—increasing not only the planet’s diameter, but also its oblateness.
The midocean ridges trending generally N-S in the Atlantic, Pacific and Indian Oceans are evidence of expansion on the E-W axis, whereas the ridges trending E-W in the South Pacific and Indian Oceans surrounding Antarctica are evidence of expansion on the N-S axis, as are the large gaps of the canyons in the North Pacific Fracture Zones (Surveyor, Mendocino, Murray, Molokai, Clarion and Clipperton FZs).
On either axis, expansion is manifested by the so-called fracture zones and transform faults, most of which are slip-strike faults or grabens formed as the ocean floors increased in area and the Earth expanded. The extreme E-W slip-strike displacements of the mid-Atlantic ridge near the Equator, and the Eltanin Fracture Zone in the South Pacific, are similar to the San Andreas Fault as evidence of the expansion mechanism.
Contrary to the belief of some investigators, continents do not drift ‘willy-nilly’ about the Earth's surface. So-called "exotic terranes" that supposedly migrated thousands of kilometers across ocean expanses (by some vague, unexplained mechanism) are nothing more than remnants of the original continent left behind or exposed when the continents split apart. As shown by the Andesite Line, Asia and Australia, as well as Europe and Africa, moved away from North and South America laterally E-W with little N-S movement, except, perhaps, near the Equator. In the same manner, Antarctica moved southward from its earlier connections with the other continents.
The history of the Indian Ocean is not so clear. It is evident from the way the Carlsberg Ridge comes out of the Gulf of Aden and then branches to the right and left, that Africa and Australia were probably connected at one time. The Ninety East Ridge, a remarkably straight geographic feature that looks like an old scar in the eastern Indian Ocean, may be an artifact of earlier stages of the Pangaean breakup when Antarctica was still attached to both Africa and Australia. (Could the Pangaean breakup have commenced in the Indian Ocean?)
Many distinguished geologists (Ahmad, Stöcklin) have pointed out that the Indian continent could not have shifted northward and 'slammed' into the Asian continent to form the Himalayas because there is no causative mechanism or motive power sufficient to cause such a collision. For support of this view, please see the statements of these two eminent geologists in the Archives Section.
© 1999, St. Clair Enterprises (Page last updated 29 Sep. 1999)