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.

Characterizing plume-plate interactions at ocean hotspots from the vertical motion history of volcanic ocean islands

2021 ◽  
Author(s):  
Kimberly Huppert ◽  
J. Taylor Perron ◽  
Leigh Royden ◽  
Michael Toomey
Keyword(s):  
Surface Deformation ◽  
Heat Budget ◽  
Hawaiian Islands ◽  
Plate Motion ◽  
Mantle Flow ◽  
Plate Boundaries ◽  
Mantle Plumes ◽  
Dynamic Topography ◽  
Geologic Record ◽  
Ocean Islands

<p>Geologic evidence of island uplift and subsidence can provide important observational constraints on the rheology, thermal evolution, and dynamics of the lithosphere and mantle – all of which have implications for understanding Earth’s heat budget, the styles of deformation that develop at plate boundaries, and the surface expression of mantle convection. Hotspot ocean islands, like the Hawaiian Islands, result from mantle plumes, which may originate as deep as the core-mantle boundary. They often host paleoshorelines, which preserve a geologic record of surface deformation, and they can also be situated far from complex plate boundaries that obscure evidence of dynamic topography – long wavelength, low amplitude topography resulting from mantle flow. Ocean islands therefore provide a unique window to deep earth processes operating today and in the geologic past.<br><br>We examine the relative contribution of lithosphere and mantle processes to surface deflection at ocean hotspots. The seafloor surrounding ocean hotspots is typically 0.5 - 2 km shallower than expected for its age over areas hundreds to >1000 km wide, but the processes generating these bathymetric swells are uncertain. Swells may result from reheating and thinning of the lithosphere and the isostatic effect of replacing colder, denser lithosphere with hotter, less dense upper mantle. Alternately, they may be supported by upward flow of ascending mantle plumes and/or hot, buoyant plume material ponded beneath the lithosphere. Because these two end-member models predict different patterns of seafloor and island subsidence, swell morphology and the geologic record of island drowning may reveal which of these mechanisms dominates the process of swell uplift. We examine swell bathymetry and island drowning at 14 hotspots and find a correspondence between island lifespan and residence time atop swell bathymetry, implying that islands drown as tectonic plate motion transports them past mantle sources of uplift. This correspondence argues strongly for dynamic uplift of the lithosphere at ocean hotspots. Our results also explain global variations in island lifespan on fast- and slow-moving tectonic plates (e.g. drowned islands in the Galápagos <4 Myr old versus islands >20 Myr old above sea level in the Canary Islands), which strongly influence island topography, biodiversity, and climate.<br><br>Over shorter timescales, paleoshorelines on hotspot ocean islands may constrain transient changes in local swell morphology. Accounting for flexural isostatic adjustment of the lithosphere to volcanic loading, we also examine patterns in the residual deflection of paleoshorelines across the Hawaiian Islands that might correspond to non-steady state behavior of the Hawaiian plume. Together, these analyses highlight the unique constraints that island paleoshorelines and topo-bathymetry can place on plume-plate interactions at ocean hotspots.</p>

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.

High-resolution constraints on LAB structure at the Blanco transform

2020 ◽  
Author(s):  
William Hawley ◽  
James Gaherty
Keyword(s):  
High Resolution ◽  
Azimuthal Anisotropy ◽  
Plate Motion ◽  
Pacific Basin ◽  
Mantle Flow ◽  
Detailed Knowledge ◽  
Plate Boundaries ◽  
Seismic Structure ◽  
The Pacific ◽  
Juan De Fuca

&lt;p&gt;Detailed knowledge of the seismic structure, fabric, and dynamics that surround the oceanic LAB continue to be refined through offshore seismic studies. Previous high-resolution studies in the Pacific basin far from plate boundaries show asthenospheric fabric that aligns neither with the lithospheric fabric (the paleo-spreading direction) nor with absolute plate motion, but rather in between. Here we present preliminary results from the Blanco Transform and Cascadia Initiative experiments, investigating the structure of the Juan de Fuca and Pacific plates on either side of the Blanco Transform. We measure ambient-noise and teleseismic Rayleigh-wave phase velocities, and solve for the period-dependent azimuthal anisotropy on either side of the transform. We will contextualize and interpret the fabrics based on mantle flow inferred from these previous Pacific basin studies.&amp;#160;&lt;/p&gt;

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;

Linking Lithospheric Structure, Mantle Flow and Intra-Plate Volcanism

2021 ◽  
Author(s):  
Thomas Duvernay ◽  
Rhodri Davies ◽  
Christopher Mathews ◽  
Angus Gibson ◽  
Stephan Kramer
Keyword(s):  
Numerical Investigation ◽  
Mantle Plume ◽  
Temporal Distribution ◽  
Mantle Flow ◽  
Mantle Plumes ◽  
Heterogeneous Distribution ◽  
Passive Margins ◽  
Lithospheric Thickness ◽  
Isolated Points ◽  
Spatio Temporal

&lt;p&gt;Several of Earth's intra-plate volcanic provinces cannot be explained solely through the classical mantle plume hypothesis. Instead, they are believed to be generated by shallower processes that involve the interplay between uppermost mantle flow and the base of Earth's heterogeneous lithosphere. The mechanisms most commonly invoked are edge-driven convection (EDC) and shear-driven upwelling (SDU), both of which act to focus upwelling flow, and the associated decompression melting, adjacent to steps in lithospheric thickness.&lt;/p&gt;&lt;p&gt;In this study, we first undertake a systematic numerical investigation, in both 2-D and 3-D, to quantify the sensitivity of EDC, SDU and their associated melting to several key controlling parameters, in the absence of mantle plumes. Our simulations demonstrate that the spatial and temporal characteristics of EDC are sensitive to the geometry and material properties of the lithospheric step, in addition to the depth-dependence of upper mantle viscosity. These simulations also indicate that asthenospheric shear can either enhance or reduce upwelling velocities and predicted melt volumes, depending upon the magnitude and orientation of flow relative to the lithospheric step. When combined, such sensitivities explain why step changes in lithospheric thickness, which are common along cratonic edges and passive margins, only produce volcanism at isolated points in space and time. Our predicted trends of melt production suggest that, in the absence of potential interactions with mantle plumes, EDC and SDU are viable mechanisms only for Earth's shorter-lived, low-volume intra-plate volcanic provinces.&lt;/p&gt;&lt;p&gt;To complement the results from our first numerical investigation, we subsequently explore how the upwelling of a mantle plume within our 3-D domain modifies the occurrence of melting, both in terms of spatio-temporal distribution and intensity. Preliminary results indicate that edges close to the location of plume impingement have their melting shut off as a result of the intense flow generated through sub-lithospheric spreading. Additionally, the heterogeneous distribution of continental lithosphere thickness constrains plume material spreading and results in melting patterns that do not directly reflect the path of the plume relative to the lithosphere, as described by classical mantle plume theory.&lt;/p&gt;

scholarly journals Effects of basal drag on subduction dynamics from 2D numerical models

2020 ◽  
Author(s):  
Lior Suchoy ◽  
Saskia Goes ◽  
Benjamin Maunder ◽  
Fanny Garel ◽  
Rhodri Davies
Keyword(s):  
Numerical Models ◽  
Force Balance ◽  
Plate Motion ◽  
Mantle Flow ◽  
Plate Motions ◽  
Flow Models ◽  
Plate Size ◽  
Modelling Studies ◽  
Subduction System

Abstract. Subducting slabs are an important driver of plate motions, yet the force balance governing subduction dynamics remains incompletely understood. Basal drag has been proposed to be a minor contributor to subduction forcing, because of the lack of correlation between plate size and velocity in observed and reconstructed plate motions. Furthermore, in single subduction system models, low basal drag, associated with a low ratio of asthenospheric to lithospheric viscosity, leads to subduction behaviour most consistent with the observation that trench migration velocities are generally low compared to convergence velocities. By contrast, analytical calculations and global mantle flow models indicate basal drag can be substantial. In this study, we revisit this problem by examining the drag at the base of the lithosphere, for a single subduction system, in 2D models with a free trench and composite non-linear rheology. We compare the behaviour of short and long plates for a range of asthenospheric and lithospheric rheologies. We reproduce results from previous modelling studies, including low ratios of trench over plate motions. However, we also find that any combination of asthenosphere and lithosphere viscosity that produces Earth-like subduction behaviour leads to a correlation of velocities with plate size, due to the role of basal drag. By examining Cenozoic plate motion reconstructions, we find that slab age and plate size are positively correlated: higher slab pull for older plates tends to be offset by higher basal drag below these larger plates. This, in part, explains the lack of plate velocity-size correlation in observations, despite the important role of basal drag in the subduction force-balance.

scholarly journals Kinematics and dynamics of the East Pacific Rise linked to a stable, deep-mantle upwelling

2016 ◽  
Vol 2 (12) ◽  
pp. e1601107 ◽  
Author(s):  
David B. Rowley ◽  
Alessandro M. Forte ◽  
Christopher J. Rowan ◽  
Petar Glišović ◽  
Robert Moucha ◽  
...  
Keyword(s):  
East Pacific Rise ◽  
Oceanic Lithosphere ◽  
Plate Motion ◽  
Mantle Flow ◽  
Plate Boundaries ◽  
Tectonic Plates ◽  
Ocean Ridges ◽  
East Pacific ◽  
The Pacific ◽  
Negative Buoyancy

Earth’s tectonic plates are generally considered to be driven largely by negative buoyancy associated with subduction of oceanic lithosphere. In this context, mid-ocean ridges (MORs) are passive plate boundaries whose divergence accommodates flow driven by subduction of oceanic slabs at trenches. We show that over the past 80 million years (My), the East Pacific Rise (EPR), Earth’s dominant MOR, has been characterized by limited ridge-perpendicular migration and persistent, asymmetric ridge accretion that are anomalous relative to other MORs. We reconstruct the subduction-related buoyancy fluxes of plates on either side of the EPR. The general expectation is that greater slab pull should correlate with faster plate motion and faster spreading at the EPR. Moreover, asymmetry in slab pull on either side of the EPR should correlate with either ridge migration or enhanced plate velocity in the direction of greater slab pull. Based on our analysis, none of the expected correlations are evident. This implies that other forces significantly contribute to EPR behavior. We explain these observations using mantle flow calculations based on globally integrated buoyancy distributions that require core-mantle boundary heat flux of up to 20 TW. The time-dependent mantle flow predictions yield a long-lived deep-seated upwelling that has its highest radial velocity under the EPR and is inferred to control its observed kinematics. The mantle-wide upwelling beneath the EPR drives horizontal components of asthenospheric flows beneath the plates that are similarly asymmetric but faster than the overlying surface plates, thereby contributing to plate motions through viscous tractions in the Pacific region.

Coupled evolution of supercontinents and lower mantle structure

2021 ◽  
Author(s):  
Xianzhi Cao ◽  
Nicolas Flament ◽  
Ömer Bodur ◽  
Dietmar Müller
Keyword(s):  
Lower Mantle ◽  
Reference Frames ◽  
Plate Motion ◽  
Motion Path ◽  
Mantle Flow ◽  
Plate Tectonic ◽  
Mantle Structure ◽  
Plate Motions ◽  
Flow Models ◽  
Over Time

&lt;p&gt;The relationships between plate motions and basal mantle structure remain poorly understood, with some models implying that the basal mantle structure has remained stable over time, while others suggest that it could be shaped by the aggregation and dispersal of supercontinents. Here we investigate the plate-basal mantle relationship through 1) building a series of end-member plate tectonic models over one billion years, and 2) creating mantle flow models assimilated by those plate models. To achieve that, we build synthetic plate tectonic models dating from 1&amp;#160;Ga to 250 Ma that we connect to an existing palaeogeographical plate reconstruction from 250 Ma to create a relative plate motion model for the last 1 Gyr, in which supercontinent breakup and reassembly occur via introversion. We consider three distinct reference frames that result in different net lithospheric rotation. We find that the flow models predict a dominant degree-2 lower mantle structure most of the time and that they are in first-order agreement (~70% spatial match) with tomographic models. Model thermochemical structures at the base of the mantle may split into smaller structures when slabs sink onto them, and smaller basal structures may merge into larger ones as a result of slab pushing. The basal thermochemical structure under the superocean is large and continuous, whereas the basal thermochemical structure under the supercontinent is smaller and progressively assembles during and shortly after supercontinent assembly. In the models, plumes also develop preferentially along the edge of the basal thermochemical structures and tend to migrate towards the interior of basal structures over time as they interact with the slabs. Lone plumes can also form away from the main thermochemical structures, often within a small network of sinking slabs. Lone plumes may migrate between basal structures. We analyse the relationship between imposed tectonic velocities and deep mantle flow, and find that at spherical harmonic degree 2, the maxima of lower mantle radial flow and temperature follow the motion path of the maxima of surface divergence. It may take ~160-240 Myr for lower mantle structure to reflect plate motion changes when the lower mantle is reorganised by slabs sinking onto basal thermochemical structures, and/or when slabs stagnate in the transition zone before sinking to the lower mantle. Basal thermochemical structures move at less than 0.6 &amp;#176;/Myr in our models with a temporal average of 0.16 &amp;#176;/Myr when there is no net lithospheric rotation, and between 0.20-0.23 &amp;#176;/Myr when net lithospheric rotation exists and is induced to the lower mantle. Our results suggest that basal thermochemical structures are not stationary, but rather linked to global plate motions and plate boundary reconfigurations, reflecting the dynamic nature of the co-evolving plate-mantle system.&lt;/p&gt;

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 Mantle Convection and Possible Mantle Plumes beneath Antarctica - Insights from Geodynamic Models and Implications for Topography

2021 ◽  
pp. M56-2020-2
Author(s):  
Eva Bredow ◽  
Bernhard Steinberger
Keyword(s):  
Mantle Plume ◽  
Seismic Tomography ◽  
Mantle Convection ◽  
Large Scale ◽  
Shear Velocity ◽  
Mantle Flow ◽  
Mantle Plumes ◽  
Dynamic Topography ◽  
West Antarctica ◽  
Geodynamic Models

AbstractThis chapter describes the large-scale mantle flow structures beneath Antarctica as derived from global seismic tomography models of the present-day state. In combination with plate reconstructions, the time-dependent pattern of paleosubduction can be simulated and is also shown from the rarely seen Antarctic perspective. Furthermore, a dynamic topography model demonstrates which kind and scales of surface manifestations can be expected as a direct and observable result of mantle convection. The last section of the chapter features an overview of the classical concept of deep-mantle plumes from a geodynamic point of view and how recent insights, mostly from seismic tomography, have changed the understanding of plume structures and dynamics over the past decades. The long-standing and controversial hypothesis of a mantle plume beneath West Antarctica is summarised and addressed with geodynamic models, which estimate the excess heat flow of a potential plume at the bedrock surface. However, the predicted heatflow is small while differences in surface heat flux estimates are large, therefore the results are not conclusive with regard to the existence of a West Antarctic mantle plume. Finally, it is shown that global mantle flow would cause tilting of whole-mantle plume conduits beneath West Antarctica such that their base is predicted to be displaced about northward relative to the surface position, closer to the southern margin of the Pacific Large Low Shear Velocity Province.

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