scholarly journals Seismic tomography, surface uplift, and the breakup of Gondwanaland: Integrating mantle convection backwards in time

2003 ◽  
Vol 4 (3) ◽  
Author(s):  
Clinton P. Conrad ◽  
Michael Gurnis
Keyword(s):  
Seismic Tomography ◽  
Mantle Convection ◽  
Surface Uplift

New Mantle Convection Models Constrained by Seismic Tomography Data

2003 ◽  
Vol 46 (6) ◽  
pp. 1106-1113 ◽  
Author(s):  
Rongshan FU ◽  
Jianhua HUANG ◽  
Shuqian DONG ◽  
Xiaohua CHANG
Keyword(s):  
Seismic Tomography ◽  
Mantle Convection ◽  
Tomography Data

scholarly journals Compositional mantle layering revealed by slab stagnation at ~1000-km depth

2015 ◽  
Vol 1 (11) ◽  
pp. e1500815 ◽  
Author(s):  
Maxim D. Ballmer ◽  
Nicholas C. Schmerr ◽  
Takashi Nakagawa ◽  
Jeroen Ritsema
Keyword(s):  
Numerical Modeling ◽  
Seismic Tomography ◽  
Upper Mantle ◽  
Lower Mantle ◽  
Mantle Convection ◽  
Global Scale ◽  
Compositional Gradient ◽  
Mantle Enrichment ◽  
Geodynamic Models ◽  
Neutrally Buoyant

Improved constraints on lower-mantle composition are fundamental to understand the accretion, differentiation, and thermochemical evolution of our planet. Cosmochemical arguments indicate that lower-mantle rocks may be enriched in Si relative to upper-mantle pyrolite, whereas seismic tomography images suggest whole-mantle convection and hence appear to imply efficient mantle mixing. This study reconciles cosmochemical and geophysical constraints using the stagnation of some slab segments at ~1000-km depth as the key observation. Through numerical modeling of subduction, we show that lower-mantle enrichment in intrinsically dense basaltic lithologies can render slabs neutrally buoyant in the uppermost lower mantle. Slab stagnation (at depths of ~660 and ~1000 km) and unimpeded slab sinking to great depths can coexist if the basalt fraction is ~8% higher in the lower mantle than in the upper mantle, equivalent to a lower-mantle Mg/Si of ~1.18. Global-scale geodynamic models demonstrate that such a moderate compositional gradient across the mantle can persist can in the presence of whole-mantle convection.

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.

Is a whole-mantle convection the key to solving the Tunguska 1908 problem?

2020 ◽  
Author(s):  
Boris R. German
Keyword(s):  
Solar Flare ◽  
Mantle Convection ◽  
Shear Velocity ◽  
Outer Core ◽  
Surface Uplift ◽  
The Earth ◽  
Eastern Australia ◽  
Solar Perturbations ◽  
Tunguska Event ◽  
The Impact

<p>It is generally accepted that the Tunguska event in Siberia on 30 June, 1908 resulted from an explosion of cosmic body. However, there is no common agreement that this bolide really existed. Moreover, registered ultra low frequency (ULF) magnetic oscillations in Kiel, Germany on 27-30 June 1908 [1] had a correlate with the 'acoustic halo' (ULF) of a solar flare [2].</p><p>Large low-shear velocity provinces (LLSVPs) are linked to so-called blobs located atop the Earth's outer core [3]. It was shown the Earth's D"-layer core-mantle boundary was perturbed by both the solar flare and an anomalous lunar-solar tide during the Tunguska 1908 event [2]. Therefore, gravitational/magnetic lunar-solar perturbations could have triggered a plume/hotspot/LIP activation by means of a LLSVPs convection.</p><p>It was suggested that planetary hotspots chains are interconnected [4]. Indeed, during the Tunguska event brightest glows were observed over the Eifel volcano and more weak one over the Yellowstone volcano (both volcanoes are associated with hotspots) [5]. In addition, day by day a slowly lifting of the earth round the diabase stones was registered in Tasmania from 7 June till 29 June, 1908 [6]. This lifting was independent from atmospheric temperature variations and terminated as soon as a blast took place in the caldera of Tunguska paleovolcano on 30 June, 1908 [5, 6]. Observations in Tasmania remained a mystery for a long time. Recently scientists discovery the Cosgrove hotspot had moved from Eastern Australia to Tasmania [7]. In our opinion, the Cosgrove did not lose its activity fully 9 My ago as previously assumed: the Darwin crater in Tasmania originated about of 803 ka years and large volume ejected glasses in/around this small crater contradicts to the impact origin [5, 8]. Therefore, we consider the underground activation of Cosgrove hotspot as a cause of surface uplift in Tasmania from 7 to 30 June 1908.</p><p>As in Tasmania, moving mantle hotspots were registered in Eastern Siberia [9]. Probably, hotspots in Tasmania (near Pacific LLSVPs) and in the Tunguska basin (near Perm LLSVPs) are interconnected. Because common hotspots thermal energy was released in/by the Tunguska paleovolcano explosion on 30 June 1908, the fluidal pressure of the Cosgrove hotspot under Tasmania was reduced, resulting in the termination of surface uplift. Since meteorites could not have caused the earth uplift in Tasmania, the impact hypothesis for the Tunguska phenomenon can be excluded. All data favor an endogenic origin of this event due to lunar-solar perturbations and the whole-mantle convection.</p><p><span>[1]. Weber L. (1908) Astronomische Nachrichten, </span><strong><span>178</span></strong><span>, 23. [2]. German B. (2010) EPSC2010-430. [3]. Duncombe J. (2019) Eos, </span><strong><span>100</span></strong><span>. [4]. Courtillot V. (1990) ISBN 9780813722474, 401. [5]. German B. (2019) ISBNs 9783981952605(in Russian)/9783981952612(in English). [6]. Scott H. (1908) Nature, </span><strong><span>78</span></strong><span>(2025), 376. [7]. Davies D. (2015) Nature, </span><strong><span>525</span></strong><span>, 511. [8]. Haines P. (2005) Australian Journal Earth Sciences, </span><strong><span>52</span></strong><span>, 481. [9]. Rosen O. (2015) ISBN 9785902754954, 148.</span></p>

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