Introduction to Whole-Earth Decompression Dynamics

For more than a century, scientists have recognized that opposing margins of continents fit together in certain ways and display geological and palaeobiological evidence of having been joined in the past [1] (Figure 1). Early in the twentieth century, Alfred Wegener proposed that the continents at one time had been united, but subsequently had separated and drifted through the ocean floor to their present positions [2]. Wegener’s theory of continental drift, vigorously opposed for half a century, was revived in the 1960s, and modified to become plate tectonics theory.

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Plate tectonics theory, presently popular despite certain unfounded fundamental assumptions, is based upon the idea that ocean floor, continuously produced at mid-oceanic ridges, moves like a conveyer belt, ultimately being “subducted” and re-circulated by assumed convection currents in the mantle [3-5] (Figure 2). Indeed, compelling evidence, e.g., seafloor magnetic striations, exists to support the idea of seafloor being continuously produced at mid-oceanic ridges, moving away from the ridges and ultimately plunging downward into oceanic trenches. To date, however, there is no direct, unambiguous evidence that mantle convection and/or mantle circulation actually takes place.In fact, there is reason to understand why mantle convection is impossible that comes from understanding what convection is all about.

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When a fluid is heated from beneath, it expands becoming lighter, less dense, than the fluid above it. This top-heavy arrangement is unstable, so fluid motions result as the fluid attempts to restore stability. The top-heavy arrangement occurs because the temperature at the bottom is hotter than at the top. This is convection. Not only is the Earth’s mantle not a fluid, but the weight of over-burden rock causes compression within the mantle, which increases with depth. Heating rock causes a miniscule increase in volume, hence miniscule decrease in density, much, much less than 1%. This is far, far too little to make the mantle top-heavy; the result is no convection at all.

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Figure 3. Density of mantle rock as a function of depth. Note the 60% increase in density at the bottom of the mantle, too great an increase for heat-expansion to cause a top-heavy arrangement.

Likewise, there is no substantial evidence that oceanic basalt can be repeatedly recycled through the mantle without being irreversibly altered. Yet, mantle convection/circulation and basalt recycling are fundamental necessities for the validity of plate tectonics. Moreover, plate tectonics theory does not in and of itself provide an energy source for geodynamic activity. In 1933, Otto C. Hilgenberg [6, 7] published his idea that in the distant past for some unknown reason the Earth was smaller, without ocean basins, and that subsequently the Earth expanded (Figure 4). An alternative to plate tectonics theory, Earth expansion theory, as espoused by S. Warren Carey [8, 9] and others, has met with resistance because of the lack of knowledge of an energy source of sufficient magnitude and because it is based upon the idea that Earth expansion occurs mainly along mid-oceanic ridges and thus occurred during the last 180 million years, as the oldest ocean floor is no older than that [10].

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Recognizing that neither plate tectonics theory nor Earth expansion theory is an adequate description of the dynamics of the Earth as a whole, J. Marvin Herndon proposed a new geodynamic theory, called Whole-Earth Decompression Dynamics [11], which reconciles certain elements of those two seemingly divergent theories into one unified theory of Earth dynamics. As viewed from the surface in idealized representation, Whole-Earth Decompression Dynamics is characterized primarily by the following two distinct, but related, processes: (i) the formation of secondary decompression cracks (often near continental margins), and (ii) the in-filling of those cracks with basalt (produced by volume decompression in the mantle), which is extruded mainly at mid-oceanic ridges, solidifies and traverses the ocean floor by gravitational creep to regions of lower gravitational potential energy, ultimately plunging downward into and in-filling distant decompression cracks.

Protoplanetary Origin of Whole-Earth Decompression Dynamics

Planets generally consist of concentric shells of matter, except Earth with its unique, two-component surface, comprised of about 41% continental rock with the balance being quite different ocean floor basalt. To date there has been no satisfactory explanation for the partial, crustal continental rock layer, except by assuming that the Earth in the distant past was smaller and subsequently expanded [6, 7]. The principal impediment to the idea of Earth expansion has been the lack of knowledge of a mechanism that could provide the necessary energy [12, 13]without departing from the known physical laws of nature [14].

In 1982, Adrian E. Scheidegger [15] stated concisely the prevailing view:"Thus, if expansion on the postulated scale occurred at all, a completely unknown energy source must be found."In 2004, J. Marvin Herndon disclosed just such an energy source that follows from fundamental considerations related to planetary formation [16-19]. Herndon [16] has demonstrated the consistency of Arnold Eucken’s 1944 concept [20] of planets raining out in the central regions of hot, gaseous protoplanets and has suggested that the Earth formed originally as a gas-giant planet quite similar to Jupiter [16]. The idea of Earth having been a Jupiter-like gas-giant follows from observations. Close-to-star gas-giant planets are observed in other planetary systems [21]. Moreover, Earth, together with its complement of lost primordial gases, comprises a protoplanetary mass remarkably similar to the mass of Jupiter. Significantly, Herndon has shown the rock-plus-alloy kernel that is now Earth, being crushed by about 300 Earth-masses of primordial gases, would be compressed to about 64 percent of its current radius, the same compression required to yield a closed, contiguous continental shell [17-19]. Upon the subsequent removal of its protoplanetary gaseous shell, the Earth would begin to decompress [17], driven by the stored energy of protoplanetary compression [11].Early during the formation of the Solar System, the primordial gasses were stripped from the inner planets, Mercury, Venus, Earth, and Mars. Herndon has suggested a mechanism, observed in nature, namely, the so-called T-Tauri stage super-intense solar wind, presumably associated with the onset of stellar thermonuclear fusion reactions. The idea is illustrated schematically in Figure 5.

Figure 5. Click here to view animated schematic representation of primordial gases being stripped from Earth by the super-intense T-Tauri solar wind.

There is evidence from nature to indicate the feasibility of such a great T-Tauri event. Figure 6 shows an outburst from the binary XZ-Tauri as observed by the Hubble Space Telescope over a period of five years. The white crescent shows the leading edge of the plume five years before time of the present image. The distance the leading edge had progressed in five years is about 130 times the distance from Earth to the Sun. Had our young Sun experienced a T-Tauri outburst of this magnitude, it would have stripped the gaseous envelopes, not only from the inner planets, but from the gas giants as well [19].

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Principles of Whole-Earth Decompression Dynamics

Decompression of the Earth may be seen as a direct consequence of the subsequent removal of hydrogen and other volatile constituents from the compressed kernel, presumably during the thermonuclear ignition of the Sun. After being stripped of such a great overburden, the Earth would rebound, tending toward a new hydrostatic equilibrium. Gravitational energy of compression, stored during the Jupiter-like proto-planetary stage, may be seen as the primary energy source for driving geotectonic activity, augmented to a much lesser extent by nuclear fission and radioactive decay energy [22, 23].

The initial whole-Earth decompression is expected to result in a global system of major primary decompression cracks appearing in the rigid crust which persist as the basalt feeders for the global, mid-oceanic ridge system. But here the similarity with Earth expansion theory ends. As the Earth subsequently decompresses, the area of the Earth’s surface increases by the formation of secondary decompression cracks, often located near the continental margins, presently identified as oceanic trenches. These secondary decompression cracks are subsequently in-filled with basalt, extruded from the mid-oceanic ridges, which traverses the ocean floor by gravitational creep, ultimately plunging into and in-filling secondary decompression cracks, as illustrated schematically in Figure 7.

Figure 7. Click here to view animated schematic representation of the main idea of Whole-Earth Decompression Dynamics. Basalt extrudes from mid-oceanic ridge (right), creeps across ocean floor, and falls into and in-fills secondary decompression crack oceanic-trench (left).

Geological Features

The principal surface manifestation of the Whole-Earth Decompression Dynamics is the in-filling of secondary decompression cracks, located mainly near continents, with basalt extruded from mid-oceanic ridges. Many of the surface observations of oceanic features and the consequences of down-plunging slabs, usually arrayed as supporting plate tectonics theory, according to Herndon [11], are consequences of Whole-Earth Decompression Dynamics. There are, however, global, fundamental differences between Whole-Earth Decompression Dynamics and plate tectonics, especially as pertains to the growth of ocean floor, to the origin of oceanic trenches, to the fate of down-plunging slabs, and to the displacement of continents.

The mid-oceanic ridge system spans the Earth and appears like stitching on a baseball (Figure 8). In Whole-Earth Decompression Dynamics mid-oceanic ridges are thought to be the sites of the original, global system of primary decompression cracks which serve as persistent extrusion-basalt feeder-channels. There is no evidence that the mid-oceanic ridge system represents the edges of mantle-convection cells as implied by plate tectonics.

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In Whole-Earth Decompression Dynamics, oceanic trenches, such as the Mariana Trench and others that rim the pacific basin, are thought to be surface manifestations of secondary decompression cracks, more or less continuously being formed as the Earth decompresses and, notably, continuously being in-filled (Figure 9). There is no evidence that oceanic trenches represent the edges of mantle-convection cells as implied by plate tectonics and no reason to believe that the more-or-less lateral motion of moving seafloor can in and of itself produce trenches. In Whole-Earth Decompression Dynamics, oceanic troughs are thought to be partially in-filled decompression cracks; oceanic troughs are inexplicable in plate tectonics.

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Since the work of Suess [1], understanding the process of mountain building has been hampered by conflicting evidence in a complex geological framework [24] and by limitations imposed through incorrect theories. For example, plate tectonics, while allowing for the development of lateral stress, is capable of admitting only asymmetric uplift by plate underthrust. Similarly, Earth expansion theory allows for symmetric uplift, but not lateral stress. In Whole-Earth Decompression Dynamics, on the other hand, both processes are possible. Lateral stress occurs for the same reasons as in plate tectonics and, additionally, occurs as a consequence of the formation of secondary decompression cracks. Symmetric uplift may also occur during decompression and asymmetric uplift by plate underthrust.

Timescale for Whole-Earth Decompression

The timescale for whole-Earth decompression is not yet known with certainty. One might think that whole-Earth decompression should have commenced promptly upon removal of protoplanetary hydrogen and other volatile constituents, but even the time of the initial primary crack formation is not known. The timescale for decompression may be related to the pre-degasification protoplanetary thermal state, to the dynamics of degasification, especially the cooling that might have been involved, to mantle properties, to the cooling that results from decompression, and to the time required to replace heat lost by decompression cooling. Further, the energy required for initiating a crack is generally considerably greater than the energy required for crack propagation.

The timescale for the Earth’s full rebounding from protoplanetary compression may be long, even extending into the present; witness, for example, the relatively minor rebounding of northern land masses, following post-Pleistocene deglaciation, being measured in thousands of years [25]. A much, much longer time may be expected for rebounding from compression due to protoplanetary-scale loading by approximately 300 Earth-masses of volatile constituents.

The Earth appears to be approaching the terminus of its decompression. If the Earth is presently decompressing, length of day measurements should show progressive lengthening. Such measurements, made with increasing precision over the last several decades, show virtually no current lengthening [26], implying no current secondary decompression crack formation. The formation of secondary decompression cracks might be episodic, though, like the release of stress by major earthquakes, or secondary crack formation may have ended forever. But major secondary decompression cracks are still conspicuously evident, for example, circum-pacific trenches (Figure 9). And, the complementary Whole-Earth Decompression Dynamicsprocess of basalt extrusion and crack in-filling continues at present.

Secondary crack formation and the in-filling of those cracks are complementary elements of the same Whole-Earth Decompression Dynamics process. Even in the absence of current secondary decompression crack formation, an estimate may be obtained of recent-period whole-Earth decompression by considering the amount of in-filling basalt presently being produced. The value obtained is consistent with length of day measurements [11]. Much higher basalt extrusion rates undoubtedly have occurred in the past, as the present estimated annual percent increase in radius, if constant over the lifetime of the Earth, would have only resulted in a 2 percent increase in radius.

New Implications from Whole-Earth Decompression Dynamics

Previously in geophysics, only three heat transport processes have been considered: conduction, radiation, and convection or, more generally, buoyancy-driven mass transport. As a consequence of Whole-Earth Decompression Dynamics, J. Marvin Herndon added a fourth, called mantle decompression thermal-tsunami [27].

Heat generated within the core from actinide decay and/or fission [18, 19] or from actinide decay within the mantle may enhance mantle decompression by replacing the lost heat of protoplanetary compression. The resulting decompression, beginning at the bottom of the mantle, will tend to propagate throughout the mantle, like a tsunami, until it reaches the impediment posed by the base of the crust. There, crustal rigidity opposes continued decompression, pressure builds and compresses matter at the mantle-crust-interface, resulting in compression heating. Ultimately, pressure is released at the surface through volcanism and through secondary decompression crack formation and/or enlargement.

Mantle decompression thermal-tsunami poses a mechanism for emplacing heat at the base of the crust, which may explain the geothermal gradient, temperature becoming greater with depth within the crust. Moreover, it may prove to be a significant energy source for earthquakes and volcanism, as these geodynamic processes appear concentrated along secondary decompression cracks.

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