Breakthrough Achieved in Explaining Why Tectonic Plates Move the Way They Do

Scripps Institution of Oceanography ^ | July 15, 2010 | Unknown

[SunkenCiv]

How Did Continents Split? Geology Study Shows New Picture
ScienceDaily
May 23, 2006

The paper -- the cover story in the latest issue of Geology, the journal of the Geological Society of America -- is the first to provide an explanation for the breaking patterns of continental plates, and uses the formation of an ocean about 500 million years ago to demonstrate that principle... Throughout Earth's history, there have been six major continental assembly and breakup events, about 500 million years apart. Currently the Earth is in breakup cycle in which the Atlantic and Indian oceans are opening, Nance said. The new study found that continents sometimes break along preexisting lines of weakness created during earlier continental collisions. Geologists had long suspected that break lines were created by the attachment of pieces onto larger land masses, but Nance and his co-authors were the first group to be able to prove this theory... Nance and his co-authors focused on these two particular breaks because they occurred along a "line of weakness" -- namely the spot where the small islands had attached to the larger land mass. As the internal structure of the continent was already less stable there than it was across the two solid outside pieces, the continent broke along this preexisting line. The scientists used geochemical "fingerprinting" to show that the small pieces of land, which today are found in the Appalachians, were originally created in an ocean. The radioactive element Samarium, which breaks down into various types of the element Neodymium, was used to determine the age of the rock (about one billion years). The amount of each element was typical of rock created in the ocean, away from larger continental masses... Adapted from materials provided by Ohio University.

Plate Tectonics May Grind To A Halt, Then Start Again
ScienceDaily
January 7, 2008

Scientists have assumed that the shifting of crustal plates has been slow but continuous over most of the Earth's history, but a new study from researchers at the Carnegie Institution suggests that plate tectonics may have ground to a halt at least once in our planet's history--and may do so again. A key aspect of plate tectonic theory is that on geologic time scales ocean basins are transient features, opening and closing as plates shift. Basins are consumed by a process called subduction, where oceanic plates descend into the Earth's mantle. Subduction zones are the sites of oceanic trenches, high earthquake activity, and most of the world's major volcanoes... Paul Silver of the Carnegie Institution's Department of Terrestrial Magnetism and former postdoctoral fellow Mark Behn (now at Woods Hole Oceanographic Institution) point out that most of today's subduction zones are located in the Pacific Ocean basin. If the Pacific basin were to close, as it is predicted to do about in 350 million years when the westward-moving Americas collide with Eurasia, then most of the planet's subduction zones would disappear with it. This would effectively stop plate tectonics unless new subduction zones start up, but subduction initiation is poorly understood. "The collision of India and Africa with Eurasia between 30 and 50 million years ago closed an ocean basin known as Tethys," says Silver. "But no new subduction zones have initiated south of either India or Africa to compensate for the loss of subduction by this ocean closure." ...Adapted from materials provided by Carnegie Institution, via EurekAlert!, a service of AAAS.

Do the continents really drift?
by William R. Corliss
Science Frontiers #26: Mar-Apr 1983

The distances between terrestrial radio telescopes can be measured with incredible accuracy by pointing the telescopes at the same celestial targets and operating them as interferometers. The distances between telescopes a continent apart can then be pegged to within 5 centimeters. For example, the distance between radio telescopes at Fort Davis, TX, and Onsala, Sweden, is 7,940,732.17 ± 0.10 meters. If North America and Europe are drifting apart several centimeters per year, this change should have been noticed since 1979, when adequate geodetic precision became available. Actually, no drift has been noted.

(Thomsen, D.E.; "Mark III Interferometer Measures Earth, Sky, and Gravity's Lens," Science News, 123:20, 1983.)

Comment. Of course, continental drift could be episodic, with the continents now static.

Glitches In The Terrestrial Conveyor Belt
by William R. Corliss
Science Frontiers #118, Jul-Aug 1998

According to plate tectonics, the earth's continents are being transported -- very slowly -- on a subterranean conveyor belt of sorts. Although plate tectonics, nee continental drift, was ridiculed 50 years ago, it has been very successful in accounting for many geological phenomena. The theory is rarely challenged these days, but there are anomalies out there.

"According to the simple plate-tectonic theory, the age of oceanic lithosphere is zero at a spreading oceanic ridge and increases with distance from the ridge. Thus the lithosphere of the central Atlantic, which current palaeogeographical reconstructions assure us began to open no earlier than 120 million years ago, has zero age at the Mid-Atlantic Ridge and, supposedly an age of about 120 million years close to the land masses of Africa and South America at the appropriate latitude. Yet, Bonatti and others (Nature, v. 380, p. 518, 1996) have now recovered samples of 140-million-year-old pelagic limestones not even from the edges of the Atlantic but right in the middle of the ocean, close to the ridge. How can this be possible?"

The only explanation (?) seems to be that this errant chunk of crust got "trapped" in the middle of the Atlantic -- like a misdirected suitcase on an airport conveyor belt.

<snip> ...the Moon clearly could not have been the satellite of the Earth then, for a total period of about 2,000 million years... Spurr points out that the face of the Moon shows two systems of great surface fractures, or faults, lying about 30 degrees from the two poles and trending from west-south-west to east-north-east. This is explained by him as a result of the halting of the Moon's rotation... Curiously, the face of the Earth, too, shows a similar structure, with the same general trend -- the Highland Boundary Fault... The poles of the Earth would also seem to have shifted place on at least three occasions, in the Cambrian, Permian, and (lastly) Quaternary Periods, brining ice and cold to previously warm lands... some mighty force made the crust of the Earth slip (the rotational stability of the axis of a mass as large as the Earth is enormous) and the position of the poles wobbled... there exists on the Moon a triple grid of surface fractures... perpendicular to each other within each grid, the grids being of different ages... Cambrian, Perm-Carboniferous, and Tertiary. [Valdemar Axel Firsoff, "Strange World of the Moon" chapter "The Earth's Fair Child or a Foundling?", 1959]