12-Midocean Ridges
MIDOCEAN RIDGES: THEIR HISTORY AND ROLE IN EXPANSION
What are now known as midocean ridges (MOR) were called "median ridges" when first discovered. Their discovery can be traced back to the German "Meteor" expedition of 1925-1927 that used an echo sounder to make thirteen east-west bottom profiles across the southern Atlantic Ocean.
Wegener mentioned the "mid-Atlantic ridge" in his 1928 book and referred to a 1927 paper in which he had examined "the first echo soundings made by the Americans over the North Atlantic." Later soundings showed this ridge to extend longitudinally the entire length of the Atlantic Ocean and it then became known as the "Mid-Atlantic Ridge" or "Atlantic Mid-Ocean Ridge." Some refer to them as "rifts," which is technically correct because they are extended fractures in the Earth's crust through which molten magma is extruded and coagulated by ocean water to form ridges of varying heights on either side of the rift.
The Danish ship "Dana" (1928-30) discovered the Carlsberg Ridge in the northwest Indian Ocean, followed by the British vessel John Murray in the early 1930's that traced the Carlsberg Ridge for 200 miles. Research by Americans with new and improved shipboard depth sounding instruments during and after World War Two quickly extended knowledge of the midocean ridges so that by the early-1960's they were known to extend for almost ~65,000 kilometers (~40,000 km) throughout all oceans. (Dr. B. E. Biermann of South Africa, an original EEE member, was a crew member for an Atlantic crossing of the MV Albatross in 1946, when the first soundings of the mid-Atlantic ridge were made.)
By 1963 Vines and Matthew reported parallel growth patterns on either side of the central ridges that were found to be magnetized with polarities that regularly reversed about every five million years or so. These magnetic reversals were found in all oceans, which proved that the Earth's magnetic field frequently switches polarity, for reasons that are still unknown. This phenomenon provided the investigators with a tool to date and compare the sediments on either side of the midocean ridges.
Sediment dating reflected increasingly older and thicker sediments the farther one moved away from the central ridge, in either direction, usually in a "mirror image" pattern, and from this they correctly deduced that magma congeals and spreads out, usually evenly to both sides of the LUV, suggesting these were "spreading ridges" forming new basaltic ocean seafloor. This discovery conceptually explained how Wegener's drifting continents were pushed apart to create the Atlantic Ocean basin over millions of years.
Heezen and Tharp's map of the World Ocean Floor depicts all of the worldwide LUV system except for a small portion that extends into the Arctic Ocean beyond Greenland, known as the Nansen Cordillera. The Heezen and Tharp map also displays convincing morphologic proof that the LUV has been the expansion mechanism that created both the Atlantic andthe Pacific Ocean basins within the past ~200 million years--an approximate age estimated from the oldest known sediment age of ~169 Ma cored in the southwest Pacific on Leg 129 of the Ocean Drilling Program (ODP) and the ~195 Ma estimate of Nakanishi, et al.
Current seafloor growth along a short stretch of the hyperactive EPR in the South Pacific at the rate of ~15.3-16.1 cm/yr is four times that of the southern Mid- Atlantic Ridge maximum growth rate of ~3.8-4 cm/yr, but there is no proof that these expansion rates have remained constant over time. Indeed, a constant velocity should not be expected. The wide variation in rates along different segments of the LUV undoubtedly fluctuates over time, as well as location, depending on internal core expansion at any given moment. The ebb and flow of volcanic eruptions around the world illustrates such fluctuations.
The full extent of ridge volcanism and "black smoker" vents discharging very hot water and minerals was not known until 1977, and new details of the ridges and vents are being discovered on a regular basis. The recent discovery of fabulous deposits of gold, silver, and other precious metals in volcanic vents off the coast of Japan will undoubtedly spark similar searches in other areas of the world's oceans.
MIDOCEAN RIDGES AND EXPANSION
However, far more important than being a source of magma, minerals, H2O, other gases, and heat, the midocean ridges (LUVs) that almost completely encircle the planet beneath the oceans are a gigantic "geosuture" that allows the planet to grow and expand in the same way that human cranial sutures permit a child's skull to grow to adulthood. The midocean ridges are, in effect, the "enabling mechanism" that permits controlled expansion of the planet.
The expansion process works like this: The total mass (weight) of the spherical Earth is omnidirectionally focused by gravity on the exact center of the planet, producing gravitationally-induced compression that heats and melts Earth's central core to form magma (molten rock). Melting of the cold, solid core is actually a distillation process that produces not only magma, but distills minerals, H2O, and other gases from the original rocks.
Magma expands in volume when heated and this expansion creates irresistible tectonic pressure straining against its confining outer shell until it breaks through a weak spot in the crust to become a volcanic vent, or fractures Earth's outer shell (midocean ridges and rift valleys are the fractures) thereby relieving internal pressure the same way "pressure safety valves" protect a boiler from exploding.
These structures enable magma to rise to the surface and erupt as a terrestrial or underwater volcano, or to be extruded at the fractures or form extended linear underwater volcanoes (LUVs). These processes slowly and inexorably increase the total surface area of the ocean basins, which increases Earth's diameter and circumference—a constantly expanding Earth. Tectonic plates are formed as a result of multiple fractures that fragment Earth's outer shell into smaller segments.
In some cases an initial surface graben may be formed, such as Valles Marineris on Mars, or Africa's Great Rift Valley, because the surface of a solid sphere does not flow or stretch like a balloon. Such grabens may well be precursors of future waterways.
Equally important, the more fundamental causative mechanism of gravitational pressure on the core that generates heat to melt core magma must be considered. For that, scientists must look at the much larger, and far more complex, process of gravitationally-driven compressive heating that melts the central core. This is the process that powers expansion tectonics--continuous and inexorable expansion of the planet--as an inevitable and unavoidable consequence of the Earth increasing in mass and diameter from incessant accretion of ~1,000-50,000 tons of meteor dust and meteorites every day. (Perhaps NASA can refine these estimates using their experiences after three decades in space.)
Accretion of additional mass is the primary causative mechanism of planetary growth that increases gravitational power and pressure on the exact center of the planet, generating compressive-heating and melting of the central core—which expands and powers expansion of the Earth. The expanding core is the greater tectonic force, but the entire process is constrained by the controlling force of gravity that maintains isostatic balance of all forces ; i.e., gravitational weight of the total mass (including ocean waters) balanced against the tectonic force of the expanding core.
The author submits that Carey's (and Wegener's) missing causative mechanism can now be defined as "the dynamic and continuous expansion of Earth's core caused by gravitationally-induced compressive heating and expansion of magma irresistibly straining to escape Earth's confining outer shell. The midocean ridges are the'enabling mechanism' that facilitates growth and expansion of the Earth."
Note
This is part 13 of a series of articles written by Lawrence S. Myers in the late 1990s on the Expanding Earth theory. Click "next" to read the subsequent article.
