Lower mantle structure from paleogeographically constrained dynamic Earth models

Bower, Dan J.; Gurnis, Michael; Seton, Maria

doi:10.1029/2012gc004267

Cited by 139 publications

(169 citation statements)

References 105 publications

Supporting

Mentioning

147

Contrasting

Order By: Relevance

“…Bower et al 2013;Zhong & Rudolph 2015). We analyse the geographic distributions and morphologies of both slow and fast clusters in order to qualitatively assess to what extent sinking slabs may control the varied morphology of lower-mantle slow structures (e.g.…”

Section: Geodynamic Implicationsmentioning

confidence: 99%

“…Bull et al 2009) to steep metastable plumes (e.g. Davaille 1999;Simmons et al 2007;Tan et al 2011;Bower et al 2013). Many physical parameters can be varied in such studies, but the most important parameters for the behaviour of a thermochemical pile are its buoyancy and viscosity contrast with the surrounding material (Deschamps & Tackley 2008).…”

Section: Geodynamic Implicationsmentioning

confidence: 99%

“…Typical scenarios are broad stable piles with low-angle slopes and plumes coming off of ridges (e.g. Bull et al 2009;Zhang et al 2010;Li et al 2014a,b) or metastable piles with steep sides and a buoyancy crossover within the pile (Tan et al 2005;Samuel & Bercovici 2006;Bower et al 2013).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Morphology of seismically slow lower-mantle structures

Cottaar¹,

Lekić²

2016

Geophysical Journal International

137

147

View full text Add to dashboard Cite

S U M M A R YLarge low shear velocity provinces (LLSVPs), whose origin and dynamic implication remain enigmatic, dominate the lowermost mantle. For decades, seismologists have created increasingly detailed pictures of the LLSVPs through tomographic models constructed with different modeling methodologies, data sets, parametrizations and regularizations. Here, we extend the cluster analysis methodology of Lekic et al., to classify seismic mantle structure in five recent global shear wave speed (V S ) tomographic models into three groups. By restricting the analysis to moving depth windows of the radial profiles of V S , we assess the vertical extent of features. We also show that three clusters are better than two (or four) when representing the entire lower mantle, as the boundaries of the three clusters more closely follow regions of high lateral V S gradients. Qualitatively, we relate the anomalously slow cluster to the LLSVPs, the anomalously fast cluster to slab material entering the lower mantle and the neutral cluster to 'background' lower mantle material. We obtain compatible results by repeating the analysis on recent global P-wave speed (V P ) models, although we find less agreement across V P models. We systematically show that the clustering results, even in detail, agree remarkably well with a wide range of local waveform studies. This suggests that the two LLSVPs consist of multiple internal anomalies with a wide variety of morphologies, including shallowly to steeply sloping, and even overhanging, boundaries. Additionally, there are indications of previously unrecognized meso-scale features, which, like the Perm anomaly, are separated from the two main LLSVPs beneath the Pacific and Africa. The observed wide variety of structure size and morphology offers a challenge to recreate in geodynamic models; potentially, the variety can result from various degrees of mixing of several compositionally distinct components. Finally, we obtain new, much larger estimates of the volume/mass occupied by LLSVPs-8.0 per cent ±0.9 (μ ± 1σ ) of whole mantle volume and 9.1 per cent ±1.0 (μ ± 1σ ) of whole mantle mass-and discuss implications for associating the LLSVPs with the hidden reservoir enriched in heat producing elements.

show abstract

Section: Geodynamic Implicationsmentioning

confidence: 99%

Section: Geodynamic Implicationsmentioning

confidence: 99%

See 1 more Smart Citation

Morphology of seismically slow lower-mantle structures

Cottaar¹,

Lekić²

2016

Geophysical Journal International

137

147

View full text Add to dashboard Cite

show abstract

“…Deep Earth mantle structures have been shown to have a significant influence on surface dynamics (Lithgow-Bertelloni & Richards 1998) and the long term nature of deep Earth features such as the Large Low Shear Velocity Provinces (LLSVP), which have been the focus of several studies (e.g. Zhang et al 2010;Bower et al 2013;Bull et al 2014).…”

Section: Discussionmentioning

confidence: 99%

“…Such radial profiles as this are typically used as first order approximations in MCM's (e.g. Bunge et al 2002;Bower et al 2013;Nerlich et al 2016). Other key model parameters are outlined in table 1.…”

Section: Model Configurationmentioning

confidence: 99%

Profiling the robustness, efficiency and limits of the forward-adjoint method for 3-D mantle convection modelling

Price¹,

Davies²

2017

Geophysical Journal International

View full text Add to dashboard Cite

SUMMARYKnowledge of Earth's past mantle structure is inherently unknown. This lack of knowledge presents problems in many areas of Earth science, including in mantle circulation modelling (MCM). As a mathematical model of mantle convection, MCM's require boundary and initial conditions. While boundary conditions are readily available from sources such as plate reconstructions for the upper surface, and as free slip at the core-mantle boundary (CMB), the initial condition is not known. MCM's have historically 'created' an initial condition using long 'spin up' processes using the oldest available plate reconstruction period available. Whilst these do yield good results when models are run to present day, it is difficult to infer with confidence results from early in a model's history. Techniques to overcome this problem are now being studied in geodynamics, such as by assimilating the known internal structure (e.g. from seismic tomography) of Earth at present day backwards in time. One such method is to use an iterative process known as the forward-adjoint method, which, while an efficient means of solving this inverse problem still strains all but the most cutting edge computational systems. In this study we endeavour to profile the effectiveness of this method using synthetic test cases as our known data source. We conclude that savings in terms of computational expense for forwardadjoint models can be achieved by streamlining the time-stepping of the calculation, as well as determining the most efficient method of updating initial conditions in the iterative scheme. Furthermore we observe that in the models presented, there exists an upper limit on the time interval over which solutions will practically converge, although this limit is likely to be linked to Rayleigh number.

show abstract

Two‐stage evolution of the Earth's mantle inferred from numerical simulation of coupled magmatism‐mantle convection system with tectonic plates

Ogawa

2014

JGR Solid Earth

View full text Add to dashboard Cite

Self-consistent numerical models are developed for a coupled magmatism-mantle convection system with tectonic plates in a two-dimensional rectangular box to understand the Earth's mantle evolution. The mantle evolves in two stages owing to decaying internal and basal heating, provided that the lithosphere is mechanically strong enough to inhibit spontaneous formation of new subduction zones by ridge push force. On the earlier stage that continues for the first 1-2 Gyr, the deep mantle is strongly heated, and hot materials there frequently ascend to the surface as bursts. The mantle bursts cause vigorous magmatism and make the lithosphere move chaotically. The thermostat effect of the vigorous magmatism keeps the average temperature in the upper mantle below about 1800 K no matter how strongly the mantle is heated. As the heating rate of the mantle declines, however, the mantle evolves into the later stage where mantle bursts subside, rigid tectonic plates emerge to move rather steadily, and subducted basaltic crusts accumulate on the core-mantle boundary to form compositionally dense piles. Hot plumes occasionally ascend from the basaltic piles to cause magmatism. It takes time on the order of one billion years for the slabs that sink into the lower mantle to return back to the upper mantle, and the long overturn time makes the thermal history of the upper mantle, which has been petrologically constrained for the Earth, distinct from that of the whole mantle. The long overturn time also makes water injected into the mantle by slabs distribute heterogeneously.

show abstract

Lower mantle structure from paleogeographically constrained dynamic Earth models

Cited by 139 publications

References 105 publications

Morphology of seismically slow lower-mantle structures

Morphology of seismically slow lower-mantle structures

Profiling the robustness, efficiency and limits of the forward-adjoint method for 3-D mantle convection modelling

Two‐stage evolution of the Earth's mantle inferred from numerical simulation of coupled magmatism‐mantle convection system with tectonic plates

Contact Info

Product

Resources

About