scholarly journals Current Plate Motions

1988 ◽  
Vol 129 ◽  
pp. 351-352
Author(s):  
Richard Gordon ◽  
Charles Demets ◽  
Seth Stein ◽  
Don Argus ◽  
Dale Woods
Keyword(s):  
Subduction Zones ◽  
Continental Drift ◽  
Geophysical Data ◽  
Plate Motion ◽  
Plate Boundaries ◽  
Transform Faults ◽  
Plate Motions ◽  
Motion Data ◽  
Motion Models ◽  
Self Consistent

The standard against which VLBI measurements of continental drift and plate motions are compared are self-consistent global models of “present-day” plate motions determined from geophysical data: marine magnetic anomalies at oceanic spreading centers, azimuths of transform faults, and orientations of earthquake slip vectors on transform faults and at subduction zones. Past global plate motion models have defined regions where the assumption that plates behave rigidly has apparently lead to systematic misfits, sometimes exceeding 10 mm/yr, of plate motion data. Here, we present some of the results from NUVEL-1, a new, self-consistent global model of present-day relative plate motions determined from a compilation and analysis of existing and new geophysical data. These data and new techniques have allowed us to eliminate nearly all statistically significant systematic misfits identified by earlier models, suggesting that the rigid-plate assumption is an excellent approximation when plate motions are averaged over several million years. Beside improving estimates of the motion on previously identified plate boundaries, we have also identified and determined motions on other boundaries whose subtle morphologies, lack of seismicity, and very slow (< 10 mm/yr) relative motions have made them difficult to detect. Here we focus on the application of VLBI measurements to help resolve plate tectonic problems and then briefly outline our results for Pacific-North America motion and plate motions in the Indian Ocean.

Geophysical review of the continental margins of eastern and western Canada

1979 ◽  
Vol 16 (3) ◽  
pp. 712-747 ◽  
Author(s):  
C. E. Keen ◽  
R. D. Hyndman
Keyword(s):  
Subduction Zones ◽  
Magnetic Data ◽  
Continental Margins ◽  
Plate Boundaries ◽  
Western Canada ◽  
Seismic Structure ◽  
Transform Faults ◽  
Crust And Upper Mantle ◽  
Plate Motions ◽  
Plate Convergence

The evolution and geophysical features of the continental margins of eastern and western Canada are reviewed in light of recent plate-tectonic concepts. The two margins are very different in age, structure, and origin. The eastern margins were formed either by rifting or by transform motion during the latest separation of the continents around the Atlantic that occurred from Jurassic to Tertiary times. Studies of these margins centre around a reconstruction of plate motions, the inception of which occurred over 70 Ma ago, and on subsequent processes such as subsidence and sedimentation. The subsidence of the margin is explicable in terms of cooling of the lithosphere and sediment loading. Deep crustal features are inferred from seismic, gravity, and magnetic data. The recognition of the ocean–continent boundary at these margins involves consideration of edge effects, magnetic quiet zones and rifting mechanisms. The western Canadian margins are present active plate boundaries. Recent geophysical studies of these margins centre around the detailed definition of the present plate boundaries and relative plate motions, and those of the recent past (about the past 10 Ma), and involve spreading ridges, transform faults, and subduction zones. The plate convergence predicted by offshore geophysical data has a pronounced effect on the continental crust and upper mantle extending several hundred kilometres inland from the coast. In southwestern Canada patterns characteristic of subduction zones are seen in seismic structure, the gravitational and magnetic fields, heat flow, and deep electrical structure.

An analytical model concerning the possible initiation of subduction between the India and Africa plates, caused by the Morondova plume

2020 ◽  
Author(s):  
Bernhard Steinberger ◽  
Douwe van Hinsbergen
Keyword(s):  
Subduction Zones ◽  
Plate Tectonics ◽  
Eastern Mediterranean ◽  
Plate Boundary ◽  
Plate Motion ◽  
Mantle Flow ◽  
Plate Motions ◽  
Subduction Initiation ◽  
Euler Pole ◽  
Geodynamic Processes

&lt;p&gt;Identifying the geodynamic processes that trigger the formation of new subduction zones is key to understand what keeps the plate tectonic cycle going, and how plate tectonics once started. Here we discuss the possibility of plume-induced subduction initiation. Previously, our numerical modeling revealed that mantle upwelling and radial push induced by plume rise may trigger plate motion change, and plate divergence as much as 15-20 My prior to LIP eruption. Here we show that, depending on the geometry of plates, the distribution of cratonic keels and where the plume rises, it may also cause a plate rotation around a pole that is located close to the same plate boundary where the plume head impinges: If that occurs near one end of the plate boundary, an Euler pole of the rotation may form along that plate boundary, with extension on one side, and convergence on the other.&amp;#160; This concept is applied to the India-Africa plate boundary and the Morondova plume, which erupted around 90 Ma, but may have influenced plate motions as early as 105-110 Ma. If there is negligible friction, i.e. there is a pre-existing weak plate boundary, we estimate that the total amount of convergence generated in the northern part of the India-Africa plate boundary can exceed 100 km, which is widely thought to be sufficient to initiate forced, self-sustaining subduction. This may especially occur if the India continental craton acts like an &amp;#8220;anchor&amp;#8221; causing a comparatively southern location of the rotation pole of the India plate. Geology and paleomagnetism-based reconstructions of subduction initiation below ophiolites from Pakistan, through Oman, to the eastern Mediterranean reveal that E-W convergence around 105 Ma caused forced subduction initiation, and we tentatively postulate that this is triggered by Morondova plume head rise. Whether the timing of this convergence is appropriate to match observations on subduction initiation as early as 105 Ma depends on the timing of plume head arrival, which may predate eruption of the earliest volcanics. It also depends on whether a plume head already can exert substantial torque on the plate while it is still rising &amp;#8211; for example, if the plate is coupled to the induced mantle flow by a thick craton.&lt;/p&gt;

Deciphering paleogeography from orogenic architecture: constructing orogens by a future closure of the Indian Ocean as thought experiment

2021 ◽  
Author(s):  
Thomas Schouten ◽  
Douwe van Hinsbergen
Keyword(s):  
Indian Ocean ◽  
Plate Tectonics ◽  
Thought Experiment ◽  
Continental Drift ◽  
Plate Motion ◽  
Plate Boundaries ◽  
Diagnostic Features ◽  
Independent Basis ◽  
Plate Deformation ◽  
The Indian Ocean

&lt;p&gt;Orogens that form at convergent plate boundaries typically consist of accreted rock units that form an incomplete archive of subducted oceanic and continental lithosphere, as well as of deformed crust of the former upper plate. Reading the construction of orogenic architecture forms the key to decipher the paleogeographic distribution of oceans and continents, as well as bathymetric and topographic features that existed thereon such as igneous plateaus, seamounts, microcontinents, or magmatic arcs. Owing to its complicated opening history, the Indian Ocean comprises a mosaic of such features that is an excellent illustration of the degree of geographic complexity that must have occurred in now-subducted oceanic realms of the geologic past and provides the ideal natural laboratory to validate interpretations of present-day orogenic architecture in terms of paleogeography. Current classification schemes of orogens divide between settings associated with termination of subduction (continent-continent collision, continent-ocean collision (obduction)) and with ongoing subduction (accretionary orogenesis), alongside intraplate orogens. Perceived diagnostic features for such classifications, particularly of collisional orogenesis, hinge on dynamic interpretations linking downgoing plate paleogeography to upper plate deformation, plate motion changes, or magmatism. Here, we show, however, that Mesozoic-Cenozoic orogens that undergo collision almost all defy these proposed diagnostic features and behave like accretionary orogens instead. To reconstruct paleogeography of subducted and upper plates, we therefore propose an alternative approach to navigating through orogenic architecture: subducted plate units comprise nappes (or m&amp;#233;langes) with Ocean Plate Stratigraphy (OPS) and Continental Plate Stratigraphy (CPS) stripped from their now-subducted or otherwise underthrust lower crustal and mantle lithospheric underpinnings. Upper plate deformation and paleogeography respond to the competition between absolute motion of the upper plate and the subducting slab. Our navigation approach through orogenic architecture aims to avoid a priori dynamic interpretations that link downgoing plate paleogeography to deformation or magmatic responses in the upper plate, to provide an independent basis for geodynamic analysis. From our analysis we identify &amp;#8216;rules of orogenesis&amp;#8217; that link the rules of rigid plate tectonics with the reality of plate deformation. We illustrate the use of these rules with a thought experiment, in which we predict two contrasting orogenic architectures that may result from the closure of the Indian Ocean and subsequent collision of the Somali, Malagasy and Indian Margins in a global continental drift scenario for a future supercontinent. We illustrate that our inferred rules (of thumb) generate orogenic architecture that is analogous to elements of modern orogens, unlocking the well-known modern geography as inspiration for developing testable hypotheses that aid interpreting paleogeography from orogens that formed since the birth of&lt;br&gt;plate tectonics.&lt;/p&gt;

Plate tectonic chain reaction constrained from noise in the Cretaceous Quiet Zone

2020 ◽  
Author(s):  
Derya Gürer ◽  
Roi Granot ◽  
Douwe J.J. van Hinsbergen
Keyword(s):  
Subduction Zones ◽  
Kinematic Model ◽  
Plate Boundary ◽  
Western Mediterranean ◽  
Plate Motion ◽  
Plate Boundaries ◽  
Plate Tectonic ◽  
Test Bed ◽  
Chain Reaction ◽  
Tectonic Plates

&lt;p&gt;The relative motions of the tectonic plates show remarkable variation throughout Earth&amp;#8217;s history. Major changes in relative motion between the tectonic plates are traditionally viewed as spatially and temporally isolated events linked to forces acting on plate boundaries (i.e., formation of same-dip double subduction zones, changes in the strength of the boundary), or thought to be associated with mantle dynamics. A Cretaceous global plate reorganization event has been postulated to have affected all major plates. The Cretaceous &amp;#8216;swing&amp;#8217; in Africa-Eurasia relative plate motion provides an ideal test-bed for assessing the temporal and spatial evolution of both relative plate motions and surrounding geological markers. Here we show a novel plate kinematic model for the closure of the Tethys Ocean by implementing intra-Cretaceous Quiet Zone time markers and combine the results with the geological constraints found along the convergent plate boundary. Our results allow to assess the order, causes and consequences of geological events and unravel a chain of tectonic events that set off with the onset of horizontally-forced double subduction ~105 Myr ago, followed by a 40 Myr long period of acceleration of the Africa relative to Eurasia that peaked at 80 Myr ago (at rates four times as high as previously predicted). This acceleration, which was likely caused by the pull of two same-dip subduction zones was followed by a sharp decrease in plate velocity, when double subduction terminated with ophiolite obduction onto the African margin. These tectonic forces acted on the eastern half of the Africa-Eurasia plate boundary, which led to counterclockwise rotation of Africa and sparked new subduction zones in the western Mediterranean region. Our analysis identifies the Cretaceous double subduction episode between Africa and Eurasia as a link in the global plate tectonic chain reaction and provides a dynamic view on plate reorganizations.&lt;/p&gt;

5. Rigid plates of lithosphere

2015 ◽  
pp. 77-88
Author(s):  
Peter Molnar
Keyword(s):  
Relative Motion ◽  
Magnetic Anomalies ◽  
Plate Motion ◽  
Plate Boundaries ◽  
Positioning System ◽  
Transform Faults ◽  
Fault Plane Solutions ◽  
The Earth ◽  
Global Positioning ◽  
Relative Plate Motion

‘Rigid plates of lithosphere’ explains that because of the lithosphere’s strength, essentially rigid plates of lithosphere move with respect to one another across the surface of the Earth. Their rigidity allows their rates of relative motion and of their total displacements to be described by rotations about axes passing through the centre of the Earth, or poles of rotation. Global Positioning System (GPS) measurements corroborate the inferences drawn both from rates of seafloor spreading determined using magnetic anomalies and from directions of relative plate motion determined using orientations of transform faults and fault plane solutions of earthquakes along plate boundaries.

Decadal Seismicity Prior to Great Earthquakes at Subduction and Transform-Fault Plate Boundaries

2021 ◽  
Author(s):  
Lynn Sykes
Keyword(s):  
Subduction Zones ◽  
Tide Gauge ◽  
Plate Boundaries ◽  
Transform Faults ◽  
Slow Slip Events ◽  
Seismic Slip ◽  
Great Earthquakes ◽  
Shallow Earthquakes ◽  
Plate Coupling ◽  
Large Earthquakes

&lt;p&gt;Decadal forerunning seismic activity is used to map great asperities that subsequently ruptured in very large, shallow earthquakes at subduction zones and transform faults. The distribution of forerunning shocks of magnitude Mw&gt;5.0 is examined for 50 mainshocks of Mw 7.5 to 9.1 from 1993 to 2020. The zones of large slip in many great earthquakes were nearly quiescent beforehand and are identified as the sites of great asperities. Much forerunning activity occurred at smaller asperities along the peripheries of the rupture zones of great and giant mainshocks. Asperities are strong, well-coupled portions of plate interfaces. Sizes of great asperities as ascertained from forerunning activity generally agree with the areas of high seismic slip as determined by others using geodetic and tide-gauge data and finite-source seismic modeling. Different patterns of forerunning activity on time scales of about 5 to 45 years are attributed to the sizes and spacing of asperities. This permits many great asperities to be mapped decades before they rupture in great and giant shocks. Rupture zones of many large earthquakes are bordered either along strike, updip, or downdip by zones of low plate coupling. Several bordering regions were sites of forerunning activity, aftershocks and slow-slip events. Several poorly coupled subduction zones, however, are characterized by few great earthquakes and little forerunning activity. The detection of forerunning and precursory activities of various kinds should be sought on the peripheries of great asperities. The manuscript can be found at &lt;strong&gt;http://www.ldeo.columbia.edu/~sykes&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Beyond Plate Tectonics: Looking at Plate Deformation with Space Geodesy

1988 ◽  
Vol 129 ◽  
pp. 341-350
Author(s):  
Thomas H. Jordan ◽  
J. Bernard Minster
Keyword(s):  
Plate Tectonics ◽  
Plate Boundary ◽  
Point Of View ◽  
Space Geodesy ◽  
Plate Motion ◽  
Plate Boundaries ◽  
Measurement Systems ◽  
Motion Models ◽  
Plate Deformation ◽  
Continental Plate

We address the requirements that must be met by space-geodetic systems to place useful, new constraints on horizontal secular motions associated with the geological deformation of the earth's surface. Plate motions with characteristic speeds of about 50 mm/yr give rise to displacements that are easily observed by space geodesy. However, in order to improve the existing plate-motion models, the tangential components of relative velocities on interplate baselines must be resolved to an accuracy of < 3 mm/yr. Because motions considered small from a geodetic point of view have rather dramatic geological effects, especially when taken up as compression or extension of continental crust, detecting plate deformation by space-geodetic methods at a level that is geologically unresolvable places rather stringent requirements on the precision of the measurement systems: the tangential components on intraplate baselines must be observed with an accuracy of < 1 mm/yr. Among the measurements of horizontal secular motions that can be made by space geodesy, those pertaining to the rates within the broad zones of deformation characterizing the active continental plate boundaries are the most difficult to obtain by conventional ground-based geodetic and geological techniques. Measuring the velocities between crustal blocks to ± 5 mm/yr on 100-km to 1000-km length scales can yield geologically significant constraints on the integrated deformation rates across continental plate-boundary zones such as the western United States. However, baseline measurements in geologically complicated zones of deformation are useful only to the extent that the endpoints can be fixed in a local kinematical frame that includes major crustal blocks. For this purpose, the establishment of local geodetic networks around major VLBI and SLR sites in active areas should receive high priority.

scholarly journals Exploring the Dynamics of Global Plate Motion Based on the Granger Causality Test

2021 ◽  
Vol 11 (17) ◽  
pp. 7853
Author(s):  
Lixin Ning ◽  
Chun Hui ◽  
Changxiu Cheng
Keyword(s):  
Energy Transfer ◽  
Granger Causality ◽  
Granger Causality Test ◽  
Test Method ◽  
Plate Motion ◽  
Plate Boundaries ◽  
Causality Test ◽  
Plate Motions ◽  
The Pacific ◽  
The Relationship

The geodynamic mechanism is the research focus and core issue of plate motions and plate tectonics. Analyzing the time series of earthquakes may help us understand the relationship between two plate boundaries and further explore movement mechanisms. Therefore, this paper uses earthquake event data and the Granger causality test method to quantitatively analyze the interaction and energy transfer relationship of plate boundaries from the viewpoint of statistics. The paper aims to explore the relationship between the pull effect and the push effect of plate motion and to provide knowledge to explore seismic energy transfer relationships, and even to predict earthquakes: (1) The directions of the global plate motion field are opposite to the directions of Granger causality between plate boundaries of the Pacific, Nazca, African, Australian, Eurasian, and Philippine plates. (2) The slab-pull force (not limited to the subduction force of the ocean plates) provides a main driving force for plate motions in the Pacific plate, Nazca plate, African plate, Australian plate, Eurasian plate, and Philippine sea plate. (3) The causality relationship and optimal lag length of energy release between plate boundaries may provide another view to forecasting earthquakes.

scholarly journals Indo-Atlantic plate accelerations around the Cretaceous-Paleogene boundary: A time-scale error, not a plume-push signal

Geology ◽  
2020 ◽  
Vol 48 (12) ◽  
pp. 1169-1173
Author(s):  
L. Pérez-Díaz ◽  
G. Eagles ◽  
K. Sigloch
Keyword(s):  
Time Scale ◽  
Plate Motion ◽  
Plate Tectonic ◽  
Flood Basalts ◽  
African Plate ◽  
Plate Motions ◽  
Motion Models ◽  
Reversal Time ◽  
Scale Error

Abstract It has been suggested that plume arrival at the base of the lithosphere introduces a push force that overwhelms the balance of torques driving plate circuits, leading to plate-tectonic reorganizations. Among the most compelling evidence in support of a “plume-push” mechanism is the apparent coincidence between eruption of the Deccan flood basalts around 67–64 Ma and a short-lived increase in Indian (and decrease in African) plate speed. Using existing and newly calculated high-resolution plate-motion models, we show that plate divergence rates briefly increased throughout the Indo-Atlantic circuit, contrary to the expected effects of plume-push. We propose that this circuit-wide spike in divergence rates is best explained as the artifact of a magnetic reversal time-scale error around the much studied Cretaceous-Tertiary boundary, and that the period spanning chrons C29–C28 lasted 70% longer than currently assumed. Corrected for this error, the residual long-term patterns of Indo-Atlantic plate motions and accompanying plate-tectonic reorganization are explicable in terms of maturation of the circuit’s spreading ridges, without invoking a significant plume-push force.

scholarly journals Hot Times in Tectonophysics: Mantle Plume Dynamics and Magmatic Perturbances

2020 ◽  
Vol 11 (2) ◽  
pp. 19
Author(s):  
Vrishin R. Soman
Keyword(s):  
Mantle Plume ◽  
Lithospheric Plate ◽  
Plate Motion ◽  
Magmatic Fluid ◽  
Mantle Flow ◽  
Plate Boundaries ◽  
Mantle Plumes ◽  
Plate Model ◽  
Plate Motions ◽  
Plume Model

Earth’s dynamic lithospheric (plate) motions often are not obvious when considered in relation to the temporal stability of the crust. Seismic radiology experiments confirm that the extreme pressures and temperatures in the mantle, and to a lesser extent the asthenosphere, result in a heterogeneously viscous rheology. Occasionally, magmatic fluid makes its way through the lithospheric plate to the surface, appearing typically as a volcano, fissure eruption, or lava flow. When occurring away from the edges of plate boundaries, these long-lasting suppliers of lava, present over millions of years, are called mantle plumes, or ‘hotspots.’ Conventional definitions of mantle plumes note that they are stationary with respect to each other and the motion of the plates, passively tracing historical plate motion in volcanic formations such as the Hawaiian-Emperor island arc – the Plate Model. In this model, mantle plumes primarily occur as a consequence of lithospheric extension.Recent empirical studies, however, have demonstrated that hotspots are not as geographically consistent as previously thought. They may move in relation to each other, as well as contribute actively toward lithospheric plate motions – the Plume Model. There is a lively, ongoing debate between the Plate and Plume hypotheses, essentially seeking to determine if mantle flow is merely a passive reaction to lithospheric plate motion (Plate Model), or whether plume activity in part drives this motion (Plume Model). More likely, it is a combination of passive and active mantle plume components that better describe the comprehensive behavior of these important and distinctive landscape forming features.

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