5° deviation created our Earth and human beings.
Following continental drift and sea floor spreading, plate breakup should be considered as the 3rd milestone. Without sea floor spreading there would be no continental drift, and without plate breakup there would be no sea floor spreading. Therefore, it should be a great significance to research the mechanism of plate breakup. Any model is to explain the key issues in reality; the model of plate breakup the author proposed can be used to explain the linear characteristics of rift valleys and oceanic ridges, which other hypotheses in terms of mantle convection, hot-spots and mantle plumes can’t explain. Moreover, every detail of the model is supported by experiments. So this model should be a good one, no matter how rough and simple it is. In fact, a way to achieve great deed is usually the simplest way, for example, E=MC2 of Einstein. In this paper, the cause of continental rift valleys and/or oceanic ridges which are products of plate breaking is inquired and as a result a model of plate breakup is proposed. In addition, this model gives a relatively simple account why Mars or Venus don’t look as our Earth have entire plate breakup and subsequent florid biological world: mainly because of the 5° deviation between Venus( or Mars) and Earth in the direction of resultant force that their lithospheric plates have gone through respectively. The 5° deviation created our Earth and human beings.
Following continental drift and sea floor spreading, plate breakup should be considered as the 3rd milestone. Without sea floor spreading there would be no continental drift, and without plate breakup there would be no sea floor spreading. Therefore, it should be a great significance to research the mechanism of plate breakup.
Since 1960’s, many scientists have also felt much interest in it and put forward some hypotheses in terms of mantle convection, hot-spots and mantle plumes, etc. I regret that these hypotheses above have a following common weakness: they can not explain a fact that the spatial arrangements of oceanic ridges and continental rift valleys are linear. Now, I shall propose a model of plate breakup for international discussion.
The synopsis of the model of plate breakup is as follows: any plate has to undergo 5 stages before breaking up; each stage owns each tectonic system respectively; these 5 tectonic systems gradually deflect 15 degrees towards the rotation axis of the Earth; after entering the 5th stage, the plate normally will be broken up, i.e., one plate will be split into two plates. Several premises must be clarified before discussing this model.
Lithospheric plates are very chipped, although much rigid. So that, as a whole, the internal frictional angle of the lithospheric plate should be assumed as:
ɸ – plate = 10° ……. (2.1)
Tectonic geologists used to make tectonic model experiments with mud or paraffin. Then, may we ask how many degrees is the angle of internal friction of mud or paraffin? In effect, the solution of focal mechanism can be interpreted very satisfactorily by two perpendicular shear cracks, itself is a powerful evidence of ɸ – plate = 10°.
The tectonic belts with strikes of N50°E, N35°E and N20°E in East Asia were named Old-, Mid- and Neo-Cathaysian, respectively(1,2). They were from old to young in ages. Obviously, their strikes were gradually deflected 15 degrees. And nowadays, the longitudinal tectonic belts of N5°E strike should be produced in East Asia because the lithosphere there is being pressed in a direction of near E – W by Pacific Plate’s underthrusting towards west. Oh, 15° style is emerged once more. Now, a clear pattern of gradually deflecting 15° is shown in Table 1(3).
Deflecting 15° has incontrovertibly proved the inheritance and the causality of Earth’s tectonic movements. There might exist a following pattern: regional tectonic lines within eastern parts of plates in the Northern Hemisphere gradually deflect 15° in counter clockwise and the ones within western parts gradually deflect 15° in clockwise, just the opposite to the Southern Hemisphere. That is, turning towards the rotation axis of the Earth.
When the Earth rotates, lithospheric plates would be squeezed mainly by a North – South horizontal component of the resultant force of the longitudinal force and gravity (4), if our Earth were a standard sphere. However, in fact, the shape of our planet is an irregular sphere, i.e., a three axis ellipsoid just like a pear (Fig. 1 (5)). Taking into account this actual situation, it might be assumed that the resultant force of the lithospheric plate within the eastern Asia might turn deflect slightly, with a direction of N5°E – S5°W (see: Table 1).
It is very important that our Earth is such an irregular sphere, which different from Venus or Mars. From this may be able to explain as same rocky sphere why Mars or Venus don’t look as our Earth have entire plate breakup and subsequent florid biological world (see discussion section).
In this force field, the model of plate breakup in East Asia would be as follows:
Since the plate was squeezed in the direction of N5°E – S5°W as mentioned above, latitudinal compressed zones were first formed.
As we all can see through experiments, E – W folds were firstly formed after rotating a globe which was coated evenly with test materials (Fig. 2(6)).
Two sets of principal shear fracture zones, as we know from experiments, were then appeared within the plate, the bisectors of their acute angles were parallel to the longitudinal force (Fig. 3(7)).
Based on a following well known formula 3.1. in rock mechanics(8)
α = 45° – ɸ / 2 ………… (3.1)
where α is an included angle between the shear fracture zone and N5°E – S5°W direction’s the maximum principal stress axis; ɸ – plate = 10° (formula 2.1).
We could know α was 40°, and then, the strike of the shear zones in the eastern part of plates within East Asia in that stage all would be N45°E. Moreover, some regional compressive belts could be derived from the shear zones（Fig. 4(9)）, according to such a law as shown by the formula 3.2(9),
β = ɸ / 2 = ɸ – plate / 2 = 10° / 2 = 5° ………… (3.2)
where β is an included angle between shear zone and compressive belt. So that, the strike of the regional compressive belts in that stage should be N50°E. Which, was the mechanical cause of the Old- Cathaysian.
where: φ = internal frictional angle; S1, S1’= shear ruptures; S2, S2’= shear ruptures under the 2nd stress field; S3, S3’= shear ruptures under the 3rd stress field
1: maximum principal stress (compressive stress) ; 2: minimum principal stress (tensile stress); 3: the secondary fold axis; 4: the 3rd fold axis; 5: erect rock stratum; 6: synclinal axis; 7: anticlinal axis; 8: reversed fold axis; 9: thrust fault; 10: overthrust fault.
Many experiments mentioned above and ones by Sih, G. C. (1973)(10) had testified the above expression.
N30°E new shear zones were then appeared in the eastern part of the plate with a deflecting angle of 15° (shown in section 2.2) from N45°E old shear zones which had been formed during the 2nd stage. And so, the new shear zones also could derive out some N35°E new regional compressive belts with an included angle of 5° shown as in formula 3.2. That, was the cause of Mid- Cathaysian.
Doerner, F. J.(1948) had pointed out that new sliding planes must deflect gradually towards the compressive stress axis under a single compression (Fig. 5(11)).
(where: S’S’ are sliding planes of earlier period; SS are new ones.)
After that, N15°E newer shear zones were appeared with a deflecting angle of 15° from the shear zones which had been formed during the 3rd stage. These zones also could derive out N20°E newer regional compressive belts with an included angle of 5° as well. That, was the cause of Neo- Cathaysian.
Stagg, K. G. (1978) indicated that the direction of crack expanding must be towards the load under single compression (Fig. 6(12)).
Finally, the two sets of shear zones which had been formed during the 4th stage, the one of strike N15°E in the eastern part and the other of strike N15°W in the western part of the plate, again deflected 15° towards the rotation axis of the Earth respectively, producing an extremely strong 0° (North – South strike) shear rupture which was parallel to the maximum principal stress axis by way of the two sets of shear planes combining into one shear plane, and thus creating a North – South direction’s whole breakup in the plate (because the shear cracks during from the 2nd stage to the 4th stage were produced by a simple shear, thereby they could not split the whole thickness of the plate ). Of course, this 0° shear rupture also could derive out its compressive regional belts of N5°E and N5°W strikes, i.e., longitudinal belts. Hence, the plate was entirely split, ending the whole breaking course.
(1). Sih, G. C. (1977) considered that under a East – West tension (i.e., under a North – South compression) a non North – South oblique crack could still be split with a direction of North – South, based on his experiments (Fig. 7(13)).
(2). The experiment by Prof. Zhang W. Y. et al.(1985) showed an axial splitting of a mud cake under a simple compression (Fig. 8(14)).
Fig. 8 seems to be an excellent epitome for the entire course of plate breakup. Why can not we look upon this result as a strong evidence in experiment for supporting the model of plate breakup the author proposed?
It is necessary to point out that the North – South shear rupture was virtually a kind of tension fractures, whereas the beginning of the tensile breaking was certainly caused by shear forces, which had been successfully stated by experiments of Prof. Zhang W. Y. et al. (1977)(7).
In fact, there were several phases during the plate splitting occurred:
General strikes of oceanic ridges or rises and continental rift valleys on the Earth nowadays for the most parts are near North – South, for example, the Atlantic Mid- Ridge, the East Africa Continental Rift Valleys, the Panxi Rifts in China, etc.
Whereas the ones of non North – South strike, either because they underwent some drift and rotation; or because they were secondary structures, e.g., the oceanic ridges of East – West strike ( as its evidence, the basement of the latitudinal seas are always only sialic).
As same rocky sphere, why Mars or Venus don’t look as our Earth have entire plate breakup and subsequent a vivid biological world?
The key lies in, I think, our Earth is a three axis ellipsoid just like a pear, whereas Venus and Mars are standard spheres. When Venus or Mars rotates, its lithospheric plates would be squeezed mainly by a North-South horizontal component of the resultant force of the longitudinal force and gravity, not N5°E – S5°W horizontal component of the resultant force on our Earth.
Just because the 5° deviation between Venus( Mars) and Earth in the direction of horizontal component of the resultant force that their lithospheric plates have gone through respectively, many things that happened on Earth can’t be recreated on Venus or Mars.
Here, on the plates within Northern Hemisphere of Venus or Mars, the two sets of shear planes in its 4th stage would be N10°E and N10°W (Table 2). After again deflected 15° towards the rotation axis respectively, in its 5th stage, two sets of new shear planes of N5°W and N5°E (not overlapping) would be appeared. So, the two sets of new shear planes in the 5th stage couldn’t combine into one shear plane and entirely split of its lithospheric plates, as did as on our Earth (see: section 3.5.).
Hence, for Venus or Mars, none of these below can be produced: extremely strong 0° (N – S strike) shear rupture → entirely split of its lithospheric plates → mantle currents arched upward along linear breakup of plate → linear convection of hot mantle → sea floor spreading → sea and ocean → water and oxygen → continental drift → life and its evolution → Human beings …
The following hypothesis has been proposed: the splitting of plates with SN strikes was just attributed to the maximum principle stress field accumulated by rotation of the Earth.
The course of the plate breakup would be as follows: any plate has to undergo 5 stages before breaking up; the 5 stages own each tectonic system respectively; these 5 tectonic systems gradually deflect 15 degrees towards the rotation axis of the Earth; after entering the 5th stage, the plate normally will be broken up, i.e., one plate will be split into two plates.
Theoretically, the significance of this paper might be its filling in the gaps in the field of plate tectonics. The author has considered that plate tectonics would consist of three parts: continental drift, sea floor spreading and plate breakup. That is because without sea floor spreading there would be no continental drift; and also without plate breakup there would be no sea floor spreading. So that, it should be a great significance to research the mechanism of plate breakup.
Moreover, the model may be able to explain as same rocky sphere why Mars or Venus don’t look as our Earth have entire plate breakup and subsequent florid biological world: mainly because of the 5° deviation between Venus( or Mars) and Earth in the direction of resultant force that their lithospheric plates have gone through respectively. The 5° deviation created our Earth and human beings.
I would like to thank Professors Van Bemmelen, R. W., Sun, D. Q., & Zhang, G. D., Sih, G. C., Zhang, W. Y., & Zhong, J. Y., Doerner, F. J.,Stagg, K. G., as well as China Wuhan Geology Institute and National Institute of Geology, Academia Sinica for their valuable experiments objectively supporting my model. I access the data from references below.
Name: Tianxi Sun
Affiliation: Professorial Senior Engineer (full professor). Suzhou Environmental Protection Bureau, China.
Author’s e-mail: click here
Author’s web profile: click here
Science & Mars Journal: Volume 4, Issue 4
Index: ISSN 2453-8760
Editorial note and originality declaration: Author confirms his ownership of copyrights of text and published images. Author declares the originality of published text and images and his authorship. The style, language and grammar was not reviewed by editorial board of journal.
In this paper is author focused on model of plate breakup. The study includes original drawings and diagrams, describing the discussed topic. We recomend to publish this paper in “Science Mars Journal” as our support of author’s study and research.