Abstract:
Abstract. Plate motion is a remarkable Earth process that is widely ascribed to two primary driving forces: ridge push and slab pull. With the release of the first- and second-order stress fields in 1989, it was found that the observed stresses are mainly distributed on the uppermost brittle part of the lithosphere. A modeling analysis, however, reveals that the stress produced by ridge push is mainly distributed in the lower part of the lithosphere. Doglioni and Panza recently showed that slab pull was inconsistent with the geometry and kinematics of plate. These findings suggest that other force is possibly responsible for plate motion and the observed stress. Here, we propose that the pressure of deep ocean water against the continental wall exerts enormous force (i.e., ocean-generated force) on the continent. The continent is fixed on top of the lithosphere, this attachment allows the ocean-generated force to laterally transfer to the lithospheric plate. We show that this force may combine the ridge push, collisional, and shearing forces to form force balances for the lithospheric plate; the calculated movements for the South American, African, North American, Eurasian, Australian, and Pacific plates are well consistent with the observed movements in both speed and azimuth, the RMS of the calculated speed against the observed speed for these plates is 0.91, 3.76, 2.77, 2.31, 7.43, and 1.95 mm/yr, respectively.Keywords:
Slab
Ridge push
Shearing (physics)
Shear force
Lithospheric flexure
Ridge push
Seafloor Spreading
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Plate motion is a remarkable Earth process and is widely ascribed to two primary driving forces: slab pull and ridge push. With the release of the first- and second-order stress fields since 1989, a few features of tectonic stresses provide strong constrain on these forces. The observed stresses are mainly distributed on the uppermost brittle part of the lithosphere. A modeling analysis, however, reveals that the stress produced by ridge push is dominantly distributed in the lower part of the lithosphere; Doglioni and Panza recently made an in-depth investigation on slab pull and found this force cannot be in accordance with observations. These findings of ridge push and slab pull suggest that there needs other force to be responsible for plate motion and tectonic stress. Here, we propose that the pressure of deep ocean water against the wall of continent yields enormous force (i.e., ocean-generated force) on the continent. The continent is fixed on the top of the lithosphere, this attachment allows ocean-generated force to be laterally transferred to the lithospheric plate. We show that this force may combine other forces to form force balances for the lithospheric plate, consequently, the African, Indian, South American, Australian, and Pacific plates obtain a movement of 4.52, 6.09, 2.11, 3.52, and 6.62 cm/yr, respectively. A torque balance modelling shows that the error between the movements calculated for 121 sample locations and the movements extracted from GSRM v.2.1 is less than 0.8 mm/yr in speed and 0.3o in azimuth.
Ridge push
Slab
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Plate motion is a remarkable Earth process and is widely ascribed to two primary driving forces: slab pull and ridge push. With the release of the first- and second-order stress fields since 1989, a few features of tectonic stresses provide strong constrain on these forces. The observed stresses are mainly distributed on the uppermost brittle part of the lithosphere. A modeling analysis, however, reveals that the stress produced by ridge push is dominantly distributed in the lower part of the lithosphere; Doglioni and Panza recently made an in-depth investigation on slab pull and found this force cannot be in accordance with observations. These findings of ridge push and slab pull suggest that there needs other force to be responsible for plate motion and tectonic stress. Here, we propose that the pressure of deep ocean water against the wall of continent yields enormous force (i.e., ocean-generated force) on the continent. The continent is fixed on the top of the lithosphere, this attachment allows ocean-generated force to be laterally transferred to the lithospheric plate. We show that this force may combine other forces to form force balances for the lithospheric plate, consequently, the African, Indian, South American, Australian, and Pacific plates obtain a movement of 4.52, 6.09, 2.11, 3.52, and 6.62 cm/yr, respectively. A torque balance modelling shows that the error between the movements calculated for 121 sample locations and the movements extracted from GSRM v.2.1 is less than 0.8 mm/yr in speed and 0.3o in azimuth.
Ridge push
Slab
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When seawater, that penetrates the lithosphere through faults and fractures at mid-ocean ridges, gets in contact with mantle rocks serpentine may form. Serpentine bearing rocks are considerably weaker than their source rock thereby causing a drastic change in the rheological strength of the affected lithosphere. Serpentinization is limited by temperature and the availability of active fluid bearing faults. Its maximum depth was previously considered not to exceed 4 km beneath the sea floor.
Yield strength envelopes (YSE) represent vertical profiles that predict the maximum stress supported by the lithosphere as a function of depth. We calculated YSEs for the axial lithosphere at an amagmatic Southwest Indian Ridge segment for different geotherms, serpentinization depths and mineralogical compositions in the ductile regime. Assuming the earthquake distribution is somehow linked to the rheological strength profile we then interpreted those YSEs that best correlate with the depth frequency distribution of local earthquakes. By doing so we could constrain the thermals structure, the mineralogical compositions and the deformation mode in the lithosphere. The YSEs show a thick mechanical lithosphere (30–35 km) at the ridge axis that is weakened in its uppermost 8-13 km due to serpentinization. Incorporating the axial morphology we propose a distinct mode of deformation that may also be applicable to other magma starved ultraslow spreading mid ocean ridge segments. Here, deformation and lithospheric accretion are essentially governed by deep reaching boundary faults that are well lubricated and hence aseismic due to extensive, deep-reaching serpentinization.
Ridge push
Lithospheric flexure
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Ridge push
Jupiter (rocket family)
Landform
Lithospheric flexure
Sill
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