The plate tectonics nonsense – and the Columbus egg?

Introduction

For more than half a century, the plate tectonics concept has been generally accepted and celebrated as the only one to explain the functioning of geodynamics conclusively. The reason for this situation is the simplicity of the model which enables just anybody, children included, to understand an alleged process inferred exclusively from seismological observations. This means that the force considered nearly exclusively for the functioning of geodynamics is caused by hypothetical “convection currents” active in the uppermost mantle, the asthenosphere.

Instead of attempting to unravel the insufficiently known mechanisms controlling the main tectonic structures, these are now, reversely, believed to obey the geodynamic concept in vogue. This kind of approach has its repercussions not only on the view of the mechanism of Wadati-Benioff zones, but also on the generation of important tectonic structures such as isoclinal folds and thrust faults which are associated with the orogenesis of folded mountain ranges. The result is a grave misconception of the basic tectonic processes active in the outer Earth. In order to examine the reliability of the concept at present in vogue the author scrutinized the tectonic structures concerned in respect to their possible coming into being on the basis of a rich literature and of own observations. The consequences of this examination are described in detail in the actual article and in previous publications of the author.¹

Strike-slip faults

It is remarkable that the whole of Eurasia and probably of Africa as well and large regions of North America are dominated by conjugate strike-slip faults indicating north-south directed maximum compressive stress. Simple strike-slip faults formed under north-south directed compressive stress in southern South America. This regularity is interpreted by the author to be related to the rotation of the Earth. Further sets of conjugate faults developed on the slopes of the European and other orogens and are clearly related to compressive stress parallel to the topographic gradient of the orogens which reveals them as products of gravity. They can be only considered as morphotectonic features. The same holds true for strike-slip faults on the slope of the bottoms of oceans where they indicate compressive stress parallel to the topographic gradient as will be shown further down for the paleo-fault and Alpine fault of New Zealand.

Thrusting and folding in folded mountain ranges

Apart from strike-slip faults, thrust faults and isoclinal folds are the most spectacular geological structures. These structures turn out to be iso- or cogenetic since they are the result of the same process in that the ductile shearing movement of isoclinal folds is often seen to be continued by the brittle movement of thrust faults (Fig. 1), or isoclinal folds change to thrust faults along strike. In both cases their character as shear folds is clearly manifested.

Fig. 1: In this cross-section from the Siegerland (Rhenohercynian; after Denckmann & Quiring 1931) the iso-/cogenetic origin of the older shear folds and younger thrust planes is evidenced by the fact that the latter are oriented parallel to the axial planes of the folds.

If isoclinal folds and thrust faults are associated with each other it becomes apparent that the thrust faults parallel the axial planes of the folds. This is illustrated in the outcrop scale (Fig. 1) as well as in the regional scale (Fig. 2) and elucidates the iso-/cogenetic origin of thrust faults and isoclinal folds. It provides clear evidence that the isoclinal folds are shear folds. This conclusion is furthermore confirmed by the fact that the thickness of the strata remains constant when measured parallel to the axial plane of the folds.

Fig. 2: In the Ruhr coal basin (after Pilger 1965, Wrede 1992) the folds and the thrust faults such as Satanella and Sutan strike parallel to each other which implies the congruent character of their movement by steep upward shearing. A conjugate set of strike-slip faults crosses the fold architecture diagonally and resulted in ENE-WSW extension which was also effective at the NNW striking extensional faults (hatched lines). Sattel: anticline.

Another convincing regional example of the mechanism of thrusting is the distribution of thrust faults in the sedimentary cover of the Rhenohercynian domain (Rhine Massif) and of strike-slip faults in the adjoining crystalline basement of the Saxothuringian domain of the Variscan mountains (Central German Crystalline Rise; Fig. 3). The strike of both kinds of faults is identical. Apparently the upper, inclined segments of the thrust faults in the cover rocks join the vertical roots of the faults in the crystalline basement, but their dip does not continue to depth, as presupposed in the plate tectonics model of thrusting. This again confirms the observation that the thrust faults are derived from shear faults, whose flanking blocks differed in their average density and developed different buoyancy.

Fig. 3: The thrust faults in the southern Rhine Massif (Rhenohercynian) are oriented parallel to the strike-slip faults in the Central German Crystalline Rise (CGCR; Saxothuringian; after Willmer et al. 1991). This implies that thrusting within the cover rock pile of the Rhine Massif was triggered by strike-slip faults within the Variscan crystalline basement. Consequently the thrust faults within the Rhine Massif must be considered to root in the strike-slip faults of the crystalline basement. They cannot continue their dip downwards which is presupposed in plate tectonics terms.

The coming into being of a vertical strike-slip fault in an orogen often causes isostatic imbalances in that the flanking blocks may differ in their average specific weight so that the specifically lighter block will be elevated. This happens during orogenesis, i. e. during the formation of a folded mountain range by the isostatic uplift of the filling of a geosyncline. The buoyant block becomes subject of gravitational extension and develops an overhang. If the uplift of the rising block continues by further vertical displacement on the strike-slip fault the overhang is truncated and a first imbricate wedge is formed. This process can be repeated several times so that more imbricate wedges are formed. The result is an imbricate thrust nappe of fan-like shape. This is clear evidence of a vertical-tectonic process whereas in the plate-tectonic concept both structures are considered to be products of compressive stress but without any physical evidence being presented. Thrusting is always controlled by the topographical gradient in that it is directed down-hill which characterizes thrusting as a morphotectonic process. It is always orthogonal to the strike of the strike-slip fault triggering thrusting.

The generation of such a nappe is demonstrated by two examples from the Variscan Mountains. The imbricate nappes of the Taunus Mountains (Taunus nappe; Fig. 4) and Harz Mountains (Wippra nappe; Fig. 5). Both nappes are located at about 300 km distance from each other in slope position of the Variscan Mountains, close to their culmination, the Central German Crystalline Rise. In both nappes the imbricate wedges show the typical increase of elevation of deeper stratigraphic (or metamorphic) levels toward the most rearward imbricate wedge. Both are characterized by a vertical fault at their rear boundary. This is typical of all imbricate thrust systems, also of those of a large order of magnitude, like e. g. the Longmen Shan thrust system (China; Fig. 6).

Fig. 4: The fan-shaped Taunus structure on the right bank of the Rhine river is characterized by its triangular cross-section, the wedge-shape of its individual components, steepening of the individual thrust planes from the front to the rear, and the vertical reverse fault as the rear boundary of the thrust nappe. The basic mechanism producing this structure is explained conclusively by the uplift of consecutively deeper stratigraphic units along the vertical strike-slip and reverse fault together with gravity spreading of the unsupported upper parts of the upfaulted block (IHS) during each phase of uplift. In every new phase of uplift the overhangs produced in this way were truncated by the upwards propagating vertical fault. Cross-section after Meyer & Stets (1975). dg: Gedinnean, dsu: Lower Siegenian, dsq: Middle Siegenian, dso: Upper Siegenian, crosses: Crystalline basement, HS: uplifted block.

Fig. 5: The Wippra imbricate thrust nappe (Harz Mountains; after Jacob & Franzke 1992) displays the same fan-shaped arrangement of the thrust planes as observed in the Taunus structure. The dip of the thrust planes between the imbricate wedges decreases towards the front of the nappe. This is explained here also by the consecutive truncation of the individul overhangs produced by the gavitative extension of the uplifted block (HS) due to the loss of its buttress during the various phases of uplift. The orientation of the cleavage within the imbricate wedges, too, changes from vertical in the hindmost wedges to dips shallowing towards the frontal wedge. This corroborates the inferred morphotectonic process of emplacement of the wedges. 1: Lower Caboniferous, 2: Silurian, 3 + 4: Ordovicean, HS uplifted block.

Fig. 6: (A) Cross-section of the Longmen Shan thrust system (after Robert et al. 2010) illustrating the different crustal thicknesses between the northwestern, Tibetan block and the southeastern, Yangtse block. Note that the inclined thrust planes are restricted to the uppermost 20 km of the crust which is inferred to be indicative of gravitative extension. (B) Cross-section of the Longmen Shan imbricate thrust system (slightly modified after Hubbard & Shaw 2009). The exposed stratigraphic units become increasingly older back from the frontal imbricate wedge. This is the consequence of the separation of imbricate wedges of increasingly deeper stratigraphic levels of the rising block and is typical of imbricate thrust systems in general. - WF: Wenchuan, BF: Beichuan, PF: Pengguan faults; Pr. Precambrian, Pz.: Paleozoic, Tr: Triassic.

Here, imbricate thrusting affected the uppermost ca. 20 km. The strike-slip fault triggering thrusting displaced the Moho discontinuity by about 20 km, and the transport width amounts to again 20 km. This confirms the nature of origin of thrust nappes by truncation and tilting of the imbricate wedges and characterizes them as products of morphotectonics. The elevated Tibetan block is covered by a thicker sequence of Precambrian and Paleozoic rocks than the Yangtse block so that an isostatic cause of the uplift of the Tibetan block is obvious.

The general mechanism of thrusting is illustrated by Fig. 7. Thrusting is characterized as a morphotectonic process initiated by body forces, but not by far-field stresses.

Fig. 7: Scheme of the thrusting mechanism - 1. Uplift of the buoyant block flanking a vertical strike-slip-fault. By gravitative extension (horizontal double-arrow) the rising block develops an overhang thus pushing aside and and pressing down the unconsolidated sediments on the lower block. 2. Due to further isostatic uplift of the buoyant block the vertical fault cuts through the overhang thus truncating the first imbricate wedge. 3. Formation of another overhang. 4. Formation of a third imbricate wedge by continued uplift and extension of the buoyant block. Folding within the imbricate wedges and erosion are not considered. The sequence of events is confirmed by the truncation of wedges at increasingly deeper stratigraphic levels with time.

The gravity nappes of the Eastern Alps are characterized by the same spacial arrangement of their stratigaphic units as the thrust nappes. Their most rearward parts exhibit the deepest stratigraphic units at their basis (Tollmann 1973). This is explained by the exceedingly vigorous isostatic uplift during orogenesis of those parts of the geosyncline where the thickest sedimentary sequences accumulated. Thus, there exists a high probability that the gravity nappes were formed originally by the same mechanism as thrust nappes, but, due to their extraordinarily strong uplift, were tilted down-hill and slid downward on the slope of the orogen.

The vergence of isoclinal folds has the same cause as that of thrust faults. Both are shown to be caused by the topography of an orogen so that they are characterized as morphotectonic features restricted to the uppermost parts of the orogen. This is documented by the fact that folds at deep crustal levels exhibit vertical axial planes (e. g. in the Tauern window, the most elevated area of the Eastern Alps) whereas the axial planes in the uppermost level of an orogen are inclined down-hill. The same holds true for thrust faulting, too. The originator of every thrust nappe is manifested by the existence of a vertical strike-slip fault as its rear boundary. It served as the trajectory to adjust to the isostatic imbalance caused by its installation. The imbricate wedges of a thrust nappe and their thrust planes show increasing dips towards the front of the thrust nappe due to the increase of burdening of the older by the younger imbricate wedges. This process is alleviated by the poor compaction of the young foreland sediments.

Isoclinal folding and thrusting are clearly vertical-tectonic processes caused by vertical movements and cannot be claimed to be caused by compressive stress as assumed by plate-tectonic considerations. The bivergence of thrust faults and isoclinal folds in orogens turns out not to be the result of compressive stress but to be a morphotectonic feature induced by the impact of gravity.

Thrusting and folding in the forelands of folded mountain ranges

In the forelands of orogens, the features of folds and thrusts differ, to a certain degree, from those of the interior parts of an orogen. As far as the tectonics of the forelands of folded mountain ranges is concerned, new insights have come out from thorough analysis. The outermost thrust nappe of an orogen generated during orogenesis has been formed in the foreland, e. g. of the Bavarian Alps (Germany) or the Northamerican Cordillera, and involved exclusively the foreland sediments. In both areas the foreland thrust nappe as well as the subjacent and adjoining sediments show some features which are different from those in the orogen. This refers to the nappe itself as well as to the material beneath and adjacent.

The Molasse nappe of Bavaria, e. g. (Fig. 8) is composed of the same sediments as those underlying and adjoining the nappe. It was formed in the same way as usual in orogens, but the nappe as well as the underlying and adjoining sediments underwent a peculiar kind of deformation. The nappe structure differs apparently from the normal structure observed in orogens in that mainly frontal thrust planes between the imbricate wedges have attained a listric shape which distinguishes them from the even thrust planes of nappes within orogens.

Fig. 8: The stratigraphic level of the bases of the imbricate wedges descending towards the rear of the Molasse nappe is clearly developed in this seismological-geological cross-sectin (after Schwerd et al. 1995, fig 10, cross-section 2). The flat squeezed-out wedge penetrates into the Molasse of the foreland parallel to the strata thus turning them up. Additionally, the apex pointing upwards follows the path of the least hydrostatic pressure, Thereby the front of the foreland nappe has been bent upwards.

The subjacent foreland sediments also show some peculiar features in that they apparently were squeezed out by the weight of the advancing Molasse nappe. Sliding or „blind“ thrusting was alleviated by the existence of a layer of clayey marl. The overridden and squeezed-out sediments thus are in a parautochthonous position. Within the Molasse nappe, however, the same even horizon responsible for sliding and underthrusting in the parautochthonous Molasse was folded. At their front the squeezed-out strata develop two different structures. The lower strata penetrated into the flat lying Molasse sequence parallel to these strata of the foreland area unaffected by the Alpine orogenesis. Thereby the originally flat-lying sediments on top of the penetrating wedge were bent upwards. In several cases higher members of the squeezed-out strata trended to reach the surface by following the least hydrostatic pressure thus developing an apex pointing to the surface. They got jammed so that several slivers of them piled up and formed a „triangle zone“. This process forced the frontal parts of the foreland nappe to be bent upwards so that the originally even, more frontal thrust planes attained a listric shape. This kind of deformation has been observed exclusively in forelands of orogens, but never in an orogen proper. It is clearly the result of squeezing-out of poorly compacted foreland sediments on a ductile layer of clayey marl under the weight of an advancing foreland nappe. The same features are also observed in the foreland of the Northamerican Cordillera.

The knowledge of the marked differences between the tectonic processes of folded mountain ranges and their forelands is of fundamental importance. Unfortunately the extraordinary tectonics of several forelands (Scottish Caledonides, Appalachians, Northamerican Cordillera) were considered by Boyer & Elliot (1982) to be characteristic of the tectonics of orogens so that these authors drew the wrong conclusion in establishing a model for the generation of thrusting in orogens proper. In fact the features typical of underhrusting by squeezing-out are met with in forelands only but never in folded mountain ranges. This grave mistake seemed to corroborate the horizontal-tectonic concept of plate tectonics and still remains to be an integrate part of this hypothesis.

Wadati-Benioff zones

Grave objections against plate tectonics arise from the concept of lithospheric plates migrating on the Earth’s surface. The basic idea of this concept is that those hypothetically migrating plates are thought to have their origin on ocean ridges as zones of „divergence”, are floating on convection currents active within the asthenosphere and are swallowed („subducted“) in zones of convergence („subduction zones“) thus merging into the mantle (Isacks, et al. 1968). Neutrally those zones are called Wadati-Benioff zones.

The true tectonic processes leading us to the formation of Wadati-Benioff zones are elucidated in an illustrative way by the special tectonic situation of the two Wadati-Benioff zones of New Zealand whose tectonic and geophysical phenomena have been investigated at a high level. They exhibit some peculiarities which suggest a conclusive explanation of the tectonic processes effective in Wadati-Benioff zones in general. A remarkable feature of these two seismoactive zones is that their deepest segmentss exhibit the same strike of about 30 degrees and are furthermore located in mutual continuation, interrupted only beneath the continental crust of South Island and the adjoining Challenger Plateau (Fig. 9).

Fig. 9: A: Ancient New Zealand (pre-Miocene), B: Intermediate stage; C: Present New Zealand. The history of the two Wadati-Benioff zones of New Zealand points to their generation at the site of a strike-slip fault, along which continental crust was juxtaposed with oceanic crust. Both seismic zones steepen towards depth, and the trace of their deepest segments forms a straight line (stippled line in C) indicating the location of the ancient strike-slip fault. It is interrupted on South Island only. At the Hikurangi zone (insets 1-4; after Anderson & Webb 1994) its bend sets in towards the south at increasingly shallower depth, and at the Puysegur zone (Fiordland; insets 5-6; after Reyners et al. 2002) in contrast towards the north. This implies in both cases the decreasing age of thrusting commensurably with right-latereal displacement by roughly 500 km along the ancient strike-slip fault which thus can be identified as having triggered thrusting. Like at continental strike-slip faults, the buoyant (here continental) block was thrust upon the opposing (here oceanic) block. The bulk of South Island is excepted from the initiation of a Wadati-Benioff zone, because the ancient fault did not juxtapose continental with oceanic crust. The Alpine fault is apparently younger than the paleo-fault and came into being as a reaction to the initiation of the two Wadati-Benioff zones. The compressive directions responsible for the generation of both strike-slip faults differ only insignificantly and are considered to be caused by the topographic gradient on the slope of the Pacific Basin.

This fact is the clue to the understanding of their coming into being. Since we know from continental thrusting that thrust nappes have their origin in isostatic adjustment movements on the two flanks of a strike-slip fault, we can infer that this fact also holds true for Wadati-Benioff zones. It has been shown by Gurnis & Hager (1988) that a Wadati-Benioff zone is the steeper already from shallow depth downward the younger it is. In such a zone of very young age, only the uppermost, thrusting segment is bent whereas the deeper segments still remain in a vertical position. Concomitantly with the advance of thrusting of the continental block onto oceanic crust, bending of the seismic zone propagates towards depth until most of the seismic zone may be bent. The trace of the deepest segment of the seismic zone thus can be reliably considered to indicate the original location of the strike-slip fault of New Zealand which triggered thrusting. This consideration is the basis to identify the location of the paleo-fault triggering the two Wadati-Benioff zones. Thus there is no indication that the seismic zone be the upper limit of a migrating lithospheric plate.

The reason why South Island of New Zealand has not been involved in the initiation of an intermediate segment between the two seismoactive zones is that it forms a coherent continental mass where thrusting was effective only at an intracontinental magnitude which comes out by minor thrusting on the Alpine fault. This evidences that Wadati-Benioff zones are only initiated where continental crust is juxtaposed with oceanic crust and thus substantiates that those zones are the product of isostatic adjustment movements. Furthermore we know from continental conditions that thrusting on strike-slip faults starts as soon as the buoyant block on its flank rises to adjust to the changed isostatic conditions and, due to gavitational extension, develops an overhang. Such is also clearly observed along the two Wadati-Benioff zones of New Zealand.

As becomes clear from the compilation of the seismological situation presented by Anderson & Webb (1994), the reach of the bend of the Hikurangi seismic zone towards depth decreases from north to south (Fig. 9). This means, in agreement with the finding of Gurnis & Hager (1988) in respect to Wadati-Benioff zones in general, that the stronger bending towards depth in the north of the Hikurangi zone indicates a higher age of its installation and passes gradually to lower ages towards south where the bending is reduced gradually to shallower depths. This can be ascribed to a gradual temporal progress of sequentional thrusting of continental crust onto oceanic crust concomitantly and commensurably with the dextral displacement on the strike-slip fault and can only be explained by nothing else than that the rise of the thrusted continental block was caused by its lower average density.

Along the Puysegur zone, too, thrusting is directed from the continental block to the oceanic block, and we observe that its downward bend increases towards north. The Puysegur zone thus indicates the same dextral shear sense on a NNE trending strike-slip fault as the Hikurangi zone. This implies that the deepest segments of both seismic zones represent the traces of parts of an ancient fault whose coming into being triggered isostatic movements. This finding is substantiated by the fact that the deep trace of this paleo-fault has its immediate and rectilinear continuation in the dextral Puysegur fault (Fig. 9) south of South Island. This fault surely is a remnant segment of the paleo-fault and was not integrated into the Puysegur Wadati-Benioff zone. It escaped thrusting because it crosses exclusively oceanic crust so that no isostatic adjustment was required. This is the first time that the former existence of an ancient fault has been detected which was a precursor of the Alpine fault. It becomes apparent that the paleo-fault triggered thrusting when it juxtaposed continental crust sequentionally with oceanic crust in the course of its dextral displacement. The initiation of the two seismic zones of New Zealand thus is clearly a product of isostatic adjustment and cannot be claimed to be the site of a downgoing lithospheric plate. The Alpine fault (e. g. Berryman 1979) as well as the older paleo-fault have been very probably generated by the exposure to WNW-ESE compressive stress parallel to the topographic gradient on the slope of the Pacific Basin. This is in agreement with the observation that the slopes of orogens (e. g. Pyrenees, Jura Mts., Northern and Southern Calcareous Alps, Carpathians, Rocky Mts.) are deformed by conjugate strike-slip faults caused by compressive stress parallel to the topographic gradient and thus can be best explained by the effect of gravity on the western slope of the Pacific Basin. The total displacement of the paleo-fault amounts to approximately 500 km.

The unique example of New Zealand tectonics is a clear proof that Wadati-Benioff zones are nothing else than zones of isostatic adjustment between blocks of continental and oceanic crust flanking a strike-slip fault. The non-existence of „subduction“ is furthermore corroborated by the general lack of a seismic zone beneath the postulated downgoing lithospheric plate, i. e. the zone of high Q or zone of low attenuation of seismic waves (Q = reciproke value of the specific attenuation factor). Instead, in the Wadati-Benioff zones of New Zealand and a number of other zones we observe a more or less gradual transition of material properties from the area beneath the seismic zone towards „normal“ mantle as indicated by the Vp/Vs-distribution (Reyners et al. 2006; Fig. 10).

Fig. 10: The 3-D Vp/Vs distribution in a cross-section through the central Hikurangi zone (after Reyners et al. 2006) evidences that, from the seismic zone or thrust plane downwards, within the high-Q zone there exists a gradual transition of increasing depletion in partial melts towards “normal” mantle. In consequence thereof and due to the lack of a sesimic zone below the high-Q zone, there is no indication of a downgoing lithospheric plate. Within the mantle wedge above the seismic zone, the Vp/Vs values increase due to the increasing accumulation of ascending melts. Dotted line: area of localized earthquake hypocentres.

The isostatic solution to solve the problem of initiation of Wadati-Benioff zones is already apparent by the fact that those zones are met with only in oceanic areas where fragments of continental crust exist. They nowhere developed in areas composed exclusively of oceanic crust such as the Atlantic Ocean which are devoid of continental crust so that no isostatic adjustments are required.

As is apparent, the amount of thrusting on the Wadati-Benioff zones of New Zealand is restricted to a certain measure. The amount of transport in the special case of North Island by about 300 km (away from the deep trace of the paleo-fault) clearly exceeds the amount of thusting to be expected. The explanation is very probably given by the existence of a subhorizontal seismic zone beneath North Island at about 35 km depth (Anderson & Webb 1994) which joins the frontal end of the Hikurangi seismic zone (Fig . 8). The excessive amount of transport can be attributed to a mechanism acting additionally to thrusting which the author tentatively ascribes to a sliding process being active on the western slope of the Pacific Basin which continues the sliding of the whole of ancient New Zealand after separation from Australia.

Initiation of Wadati-Benioff zones apparently follows the same mechanism as can be inferred for thrust faulting in continental orogens. Thus in the Bavarian Molasse thrust nappe, Schwerdt (1996) reports sinistral displacement between the ENE striking imbricate wedges which means that horizontal displacement indicates continuous movement along the strike-slip fault during the whole process of thrusting. Thrusting is the result of secondary vertical isostatic movement on a strike-slip fault and gravitational spreading of the uplifted block. In the same way, along a number of Wadati-Benioff zones thrusting alone has not been observed but also horizontal displacement. This caused Fitch (1972) to draft a speculative model of „oblique convergence“ in order to explain this seemingly simultaneous coincidence of two manners of seismically indicated movement. He attributes the mechanism of Wadati-Benioff zones or zones of “plate consumption” to a process of decoupling in which only the component of slip normal to the plate margin is considered to be represented by underthrusting whereas at least a fraction of slip parallel to the plate margin results in transcurrent movements. This model of two simultaneous movements caused exclusively by compressive stress has never been substantiated by experiments. Instead it is now shown that there are two different kinds of movement taking place simultaneously. The newly inferred mechanism corroborates that Wadati-Benioff zones are triggered by a vertical strike-slip fault causing the specifically lighter continental block to rise. This results in gravitative extension of the risen block and leads to its overthrusting onto the opposing lower oceanic block. Just as in the orogens, thrusting in the realm at the contact of oceanic and continental crust is clearly a morphotectonic process, too.

Conclusions

The spherical shape of the Earth is obviously caused by gravitation. This force is responsible for isostatic movements which result in the generation of isoclinal folds and thrust faults during an orogenesis. Gravitation also causes morphotectonic features such as vergences and conjugate strike-slip faults in slope position of orogens. The centrifugal force causes not only the flattening of the polar regions, but also the installation of sets of conjugate strike-slip faults indicating north-south directed compressive stress. This force has not been included at all in the plate-tectonic considerations.

For the activity of a force effectuating the migration of lithospheric plates no evidence can be substantiated. There is not the least indication of the activity of convection currents in the asthenosphere. Wadati-Benioff zones cannot be the site of a downgoing lithospheric plate migrating on the Earth’s surface due to a number of circumstances:

• There is no proof of zones of „divergence“ from where continental blocks could originate; those zones, the midoceanic ridges, are, with high probalility, of a different origin; remnants which could prove the former existence of continental blocks are entirely missing;
• There is no evidence of a downgoing plate in a zone of “convergence” (Wadati-Benioff zone). This would require a second seismic zone at the bottom of the hypothetical plate. Instead there is, at least in some better investigated cases, a gradual transition of the material properties beneath the high-Q zone down to the „normal“ mantle; Wadati-Benioff zones are entirely local phenomena and cannot be attributed to imaginary global migrations of lithospheric plates on top of convection currents;
• There is no conclusive explanation of a force being capable to force a plate of 80-100 km thickness down into the mantle;
• There is no explanation of the fact that Wadati-Benioff zones are not developed in areas exclusively composed of oceanic crust such as the Atlantic Ocean. The simple reason is that, in oceanic areas devoid of continental crust, no isostatic adjustments are required.

At a closer view it becomes apparent that plate tectonics is based only on wholesale assumptions but has not been capable to present concrete examples of the validity of assertions concerning the coming into being of structures such as folds, thrust faults, or Wadati-Benioff zones. That concept turns out to be just a rough sketch of immature ideas lacking a relation to the physical reality.

The findings of the author are not reconcilable with plate tectonics which requires definitely an entirely different, realistic view. His analyses reveal that thrusting in orogens as well as in Wadati-Benioff zones is an exclusively gravitative, isostatically induced process being triggered by the activity of a strike-slip fault. Plates of lithosphere migrating on the Earth’s surface are nothing but a pure illusion. In the foregoing it has been shown that the adventurous concept of plate migrations has the disastrous consequence that the complete tectonic fundament has been turned upside down. By accepting the plate tectonic hypothesis, a number of physical laws and geological facts has been heavily violated. This hypothesis has been generally accepted and celebrated as the final solution of the geotectonic problems. As from the final conclusion of the author’s analyses it turns out that geodynamics is not dominated by horizontal but by vertical tectonics.

This and much more in: Die globale Tektonik – was die Erdschale wirklich antreibt (Global tectonics – what really drives the skin of the Earth), with 61 figures (explanations also in English) and a synopsis in English.

Literature