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the Mid-Atlantic Ridge (Original)

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Author Topic: the Mid-Atlantic Ridge (Original)  (Read 13453 times)
Carolyn Silver
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Posts: 4611

« Reply #60 on: July 28, 2008, 11:39:50 pm »

Emergence and submergence

Vertical tectonics

The theosophical tradition teaches that the earth's crust is constantly rising or sinking, usually slowly but at times with cataclysmic intensity. There is a constant alternation of land and water: as one portion of the dry land is submerged, new land emerges elsewhere. Blavatsky writes:

Elevation and subsidence of continents is always in progress. The whole coast of South America has been raised up 10 to 15 feet and settled down again in an hour. Huxley has shown that the British islands have been four times depressed beneath the ocean and subsequently raised again and peopled. The Alps, Himalayas and Cordilleras were all the result of depositions drifted on to sea-bottoms and upheaved by Titanic forces to their present elevation. The Sahara was the basin of a Miocene sea. Within the last five or six thousand years the shores of Sweden, Denmark and Norway have risen from 200 to 600 feet; in Scotland there are raised beaches with outlying stacks and skerries surmounting the shore now eroded by the hungry wave. The North of Europe is still rising from the sea and South America presents the phenomenon of raised beaches over 1,000 miles in length, now at a height varying from 100 to 1,300 feet above the sea-level. On the other hand, the coast of Greenland is sinking fast, so much so that the Greenlander will not build by the shore. All these phenomena are certain. Why may not a gradual change have given place to a violent cataclysm in remote epochs? -- such cataclysms occurring on a minor scale even now (e.g., the case of Sunda island with 80,000 Malays*).[1]
*A reference to the massive eruption in 1883 of the volcano on the island of Krakatoa in the Sunda Strait. It created a tsunami, or giant sea wave, that swept away more than 30,000 people on the islands of Java and Sumatra.

Blavatsky also quotes the following from a contemporary scientist:

forces are unceasingly acting, and there is no reason why an elevating force once set in action in the centre of an ocean should cease to act until a continent is formed. They have acted and lifted out from the sea, in comparatively recent geological times, the loftiest mountains on earth. . . . Sea-beds have been elevated 1,000 fathoms and islands have risen up from the depths of 3,000 fathoms . . . [2]
The existence of former continental landmasses in the present oceans may be at odds with plate-tectonic dogma but, as shown below, it is supported by mounting evidence.
    Classical plate tectonics seeks to explain all geologic structures primarily in terms of simple horizontal movements of lithospheric plates -- their rifting, extension, collision, and subduction. But random plate interactions are unable to explain the periodic character of geological processes, i.e. the geotectonic cycle, which sometimes operates on a global scale. Nor can they explain the large-scale uplifts and subsidences that have characterized the evolution of the earth's crust, especially those occurring far from 'plate boundaries' such as in continental interiors, and vertical oscillatory motions involving vast regions. The presence of marine strata thousands of meters above sea level (e.g. near the summit of Mount Everest) and the great thicknesses of shallow-water sediment in some old basins indicate that vertical crustal movements of at least 9 km above sea level and 10-15 km below sea level have taken place.
    Major vertical movements have also occurred along continental margins. For example, the Atlantic continental margin of North America has subsided by up to 12 km since the Jurassic. In Barbados, Tertiary coals representing a shallow-water, tropical environment occur beneath deep-sea oozes, indicating that during the last 12 million years, the crust sank to over 4-5 km depth for the deposition of the ooze and was then raised again. A similar situation occurs in Indonesia, where deep-sea oozes occur above sea level, sandwiched between shallow-water Tertiary sediments.
    The primary mountain-building mechanism in plate tectonics is lateral compression caused by collisions -- of continents, island arcs, oceanic plateaus, seamounts, and ridges. In this model, subduction proceeds without mountain building until collision occurs, whereas in the noncollision model subduction alone is supposed to cause mountain building. As well as being mutually contradictory, both models are inadequate, as several supporters of plate tectonics have admitted. The noncollision model fails to explain how continuous subduction can give rise to discontinuous mountain building, while the collision model is challenged by occurrences of mountain building where no continental collision can be assumed, and it fails to explain contemporary mountain-building activity along such chains as the Andes and around much of the rest of the Pacific rim.
    Asia supposedly collided with Europe in the late Paleozoic, producing the Ural mountains, but abundant geological field data demonstrate that the Siberian and East European (Russian) platforms have formed a single continent since Precambrian times. One geological textbook admits that the plate-tectonic reconstruction of the formation of the Appalachian mountains in terms of three successive collisions of North America seems 'too implausible even for a science fiction plot'. C.D. Ollier states that fanciful plate-tectonic explanations ignore all the geomorphology and much of the known geological history of the Appalachians. He also says that of all the possible mechanisms that might account for the Alps, the collision of the African and European plates is the most naive [3].
    The Himalayas and the Tibetan Plateau were supposedly uplifted by the collision of the Indian plate with the Asian plate. However, this fails to explain why the beds on either side of the supposed collision zone remain comparatively undisturbed and low-dipping, whereas the Himalayas have been uplifted, supposedly as a consequence, some 100 km away, along with the Kunlun mountains to the north of the Tibetan Plateau. River terraces in various parts of the Himalayas are almost perfectly horizontal and untilted, suggesting that the Himalayas were uplifted vertically, rather than as the result of horizontal compression.
    There is ample evidence that mantle heat flow and material transport can cause significant changes in crustal thickness, composition, and density, resulting in substantial uplifts and subsidences. This is emphasized in many of the alternative hypotheses to plate tectonics. Plate tectonicists, too, increasingly invoke mantle diapirism and related upwelling processes as a mechanism for vertical crustal movements.
    Plate tectonics predicts simple heat-flow patterns around the earth. There should be a broad band of high heat flow beneath the full length of the midocean rift system, and parallel bands of high and low heat flow along the Benioff zones. Intraplate regions are predicted to have low heat flow. The pattern actually observed is quite different. There are criss-crossing bands of high heat flow covering the entire surface of the earth. Intra-plate volcanism is usually attributed to 'mantle plumes' -- upwellings of hot material from deep in the mantle. The movement of plates over the plumes is said to give rise to hotspot trails (chains of volcanic islands and seamounts). Such trails should therefore show an age progression from one end to the other, but good age progressions are very rare, and a large majority show little or no age progression. H.C. Sheth has argued that the plume hypothesis is ill-founded, artificial, and invalid, and has led earth scientists up a blind alley [4].
    A major new hypothesis of geodynamics is surge tectonics, which rejects both seafloor spreading and continental drift [5]. Surge tectonics postulates that all the major features of the earth's surface, including rifts, foldbelts, metamorphic belts, and strike-slip zones, are underlain by shallow (less than 80 km) magma chambers and channels (known as 'surge channels'). Seismotomographic data suggest that surge channels form an interconnected worldwide network, which has been dubbed 'the earth's cardiovascular system'. Active surge channels are characterized by high heat flow and microearthquakes. Magma from the asthenosphere flows slowly through active channels at the rate of a few centimeters a year. This horizontal flow is demonstrated by two major surface features: linear, belt-parallel faults, fractures, and fissures; and the division of tectonic belts into fairly uniform segments. The same features characterize all lava flows and tunnels, and have also been observed on Mars, Venus, and several moons of the outer planets.
    Surge tectonics postulates that the main cause of geodynamics is lithosphere compression, generated by the cooling and contraction of the earth.* As compression increases during a geotectonic cycle, it causes the magma to move through a channel in pulsed surges and eventually to rupture it, so that the contents of the channel surge bilaterally upward and outward to initiate tectogenesis. The asthenosphere (in regions where it is present) alternately contracts during periods of tectonic activity and expands during periods of tectonic quiescence. The earth's rotation, combined with differential lag between the more rigid lithosphere above and the more fluid asthenosphere below, causes the fluid or semifluid materials to move predominantly eastward.

*Earth scientists hold widely divergent views on the changes in size that the earth has undergone since its formation. From a theosophical perspective, after its formation in an ethereal state some 2 billion years ago, the earth gradually physicalized and contracted to some extent. This downward arc of the earth's evolution came to an end a few million years ago, and the upward arc of reetherealization began. The earth may be expected to expand slightly as the forces of attraction begin to relax.
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