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Animation showing LLSVPs as inferred using seismic tomography^[1]

Large low-shear-velocity provinces (LLSVPs), also called large low-velocity provinces (LLVPs) or superplumes, are characteristic structures of parts of the lowermost mantle, the region surrounding the outer core deep inside the Earth.^[2] These provinces are characterized by slow shear wave velocities and were discovered by seismic tomography of deep Earth. There are two main provinces: the African LLSVP and the Pacific LLSVP, both extending laterally for thousands of kilometers and possibly up to 1,000 kilometres vertically from the core–mantle boundary. These have been named Tuzo and Jason respectively, after Tuzo Wilson and W. Jason Morgan, two geologists acclaimed in the field of plate tectonics.^[3] The Pacific LLSVP is 3,000 kilometers (1,900 miles) across and underlies four hotspots on Earth's crust that suggest multiple mantle plumes underneath.^[4] These zones represent around 8% of the volume of the mantle, or 6% of the entire Earth.^[1]

Other names for LLSVPs and their superstructures include superswells, superplumes, thermo-chemical piles, or hidden reservoirs, mostly describing their proposed geodynamical or geochemical effects. For example, the name "thermo-chemical pile" interprets LLSVPs as lower-mantle piles of thermally hot and/or chemically distinct material. LLSVPs are still relatively mysterious, and many questions remain about their nature, origin, and geodynamic effects.^[5]

Seismological modeling

Directly above the core–mantle boundary is a 200 kilometers (120 miles) thick layer of the lower mantle. This layer is known as the D″ ("D double-prime" or "D prime prime") or degree two structure.^[6] LLSVPs were discovered in full mantle seismic tomographic models of shear velocity as slow features at the D″ layer beneath Africa and the Pacific.^[7] The global spherical harmonics of the D″ layer are stable throughout most of the mantle but anomalies appear along the two LLSVPs. By using shear wave velocities, the locations of the LLSVPs can be verified, and a stable pattern for mantle convection emerges. This stable configuration is responsible for the geometry of plate motions at the surface.^[8]

The LLSVPs lie around the equator, but mostly on the Southern Hemisphere. Global tomography models inherently result in smooth features; local waveform modeling of body waves, however, has shown that the LLSVPs have sharp boundaries.^[9] The sharpness of the boundaries makes it difficult to explain the features by temperature alone; the LLSVPs need to be compositionally distinct to explain the velocity jump. Ultra-low velocity zones at smaller scales have been discovered mainly at the edges of these LLSVPs.^[10]

By using the solid Earth tide, the density of these regions has been determined. The bottom two thirds are 0.5% denser than the bulk of the mantle. However, tidal tomography cannot determine how the excess mass is distributed; the higher density may be caused by primordial material or subducted ocean slabs.^[11] The African LLSVP may be a potential cause for the South Atlantic Anomaly.^[12]

Origins

Several hypotheses have been proposed for the origin and persistence of LLSVPs, depending on whether the provinces represent purely thermal unconformities (i.e. are isochemical in nature, of the same chemical composition as the surrounding mantle) or represent chemical unconformities as well (i.e. are thermochemical in nature, of different chemical composition from the surrounding mantle). If LLSVPs represent purely thermal unconformities, then they may have formed as large mantle plumes of hot, upwelling mantle. However, geodynamical studies predict that isochemical upwelling of a hotter, lower viscosity material should produce long, narrow plumes,^[13] unlike the large, wide plumes seen in LLSVPs. It is important to remember, however, that the resolution of geodynamical models and seismic images of Earth's mantle are very different.^[14]

The current leading hypothesis for the LLSVPs is the accumulation of subducted oceanic slabs. This corresponds with the locations of known slab graveyards surrounding the Pacific LLSVP. These graveyards are thought to be the reason for the high velocity zone anomalies surrounding the Pacific LLSVP and are thought to have formed by subduction zones that were around long before the dispersion—some 750 million years ago—of the supercontinent Rodinia. Aided by the phase transformation, the temperature would partially melt the slabs to form a dense melt that pools and forms the ultra-low velocity zone structures at the bottom of the core-mantle boundary closer to the LLSVP than the slab graveyards. The rest of the material is then carried upwards via chemical-induced buoyancy and contributes to the high levels of basalt found at the mid-ocean ridge. The resulting motion forms small clusters of small plumes right above the core-mantle boundary that combine to form larger plumes and then contribute to superplumes. The Pacific and African LLSVP, in this scenario, are originally created by a discharge of heat from the core (4000 K) to the much colder mantle (2000 K); the recycled lithosphere is fuel that helps drive the superplume convection. Since it would be difficult for the Earth's core to maintain this high heat by itself, it gives support for the existence of radiogenic nuclides in the core, as well as the indication that if fertile subducted lithosphere stops subducting in locations preferable for superplume consumption, it will mark the demise of that superplume.^[4]

Another proposed origin for the LLSVPs is that their formation is related to the giant-impact hypothesis, which states that the Moon formed after the Earth collided with a planet-sized body called Theia.^[15] The hypothesis suggests that the LLSVPs may represent fragments of Theia's mantle which sank through to Earth's core-mantle boundary.^[15] The higher density of the mantle fragments is due to their enrichment in iron(II) oxide with respect to the rest of Earth's mantle. This higher iron(II) oxide composition would also be consistent with the isotope geochemistry of lunar samples, as well as that of the ocean island basalts overlying the LLSVPs.^[16]^[17]

Dynamics

Geodynamic mantle convection models have included compositional distinctive material. The material tends to get swept up in ridges or piles.^[10] When including realistic past plate motions into the modeling, the material gets swept up in locations that are remarkably similar to the present day location of the LLSVPs.^[18] These locations also correspond with known slab graveyard locations.

These types of models, as well as the observation that the D″ structure of the LLSVPs is orthogonal to the path of true polar wander, suggest these mantle structures have been stable over large amounts of time. This geometrical relationship is consistent with the position of Pangaea and the formation of the current geoid pattern due to continental break-up from the superswell below.^[8]

However, the heat from the core is not enough to sustain the energy needed to fuel the superplumes located at the LLSVPs. There is a phase transition from perovskite to post-perovskite from the down welling slabs that causes an exothermic reaction. This exothermic reaction helps to heat the LLSVP, but it is not sufficient to account for the total energy needed to sustain it. So it is hypothesized that the material from the slab graveyard can become extremely dense and form large pools of melt concentrate enriched in uranium, thorium, and potassium. These concentrated radiogenic elements are thought to provide the high temperatures needed. So, the appearance and disappearance of slab graveyards predicts the birth and death of an LLSVP, potentially changing the dynamics of all plate tectonics.^[4]

References

^ ^a ^b Cottaar; Lekic (2016). "Morphology of lower mantle structures". Geophysical Journal International. 207 (2): 1122–1136. Bibcode:2016GeoJI.207.1122C. doi:10.1093/gji/ggw324.
^ Garnero, Edward J.; McNamara, Allen K.; Shim, Sang-Heon (2016). "Continent-sized anomalous zones with low seismic velocity at the base of Earth's mantle". Nature Geoscience. 9 (7): 481–489. Bibcode:2016NatGe...9..481G. doi:10.1038/ngeo2733.
^ Lau, Harriet; Al-Attar, David (2021-12-01). "Weighing TUZO and JASON individually". AGU Fall Meeting Abstracts. 2021: DI13A–05. Bibcode:2021AGUFMDI13A..05L.
^ ^a ^b ^c Maruyama; Santosh; Zhao (January 2007). "Superplume, supercontinent, and post-perovskite: Mantle dynamis and anti-plate tectonics on the Core-Mantle Boundary". Gondwana Research. 11 (1–2): 7–37. Bibcode:2007GondR..11....7M. doi:10.1016/j.gr.2006.06.003.
^ Davies, D. R.; Goes, S.; Lau, H. C. P. (2015), Khan, Amir; Deschamps, Frédéric (eds.), "Thermally Dominated Deep Mantle LLSVPs: A Review", The Earth's Heterogeneous Mantle: A Geophysical, Geodynamical, and Geochemical Perspective, Cham: Springer International Publishing, pp. 441–477, doi:10.1007/978-3-319-15627-9_14, ISBN 978-3-319-15627-9, retrieved 2024-04-09
^ Peltier, W.R. (2007). "Mantle dynamics and the D″ layer implications of the post-perovskite phase" (PDF). In Kei Hirose; John Brodholt; Thome Lay; David Yuen (eds.). Post-Perovskite: The Last Mantle Phase Transition. AGU Geophysical Monographs. Vol. 174. American Geophysical Union. pp. 217–227. ISBN 978-0-87590-439-9. Archived (PDF) from the original on 2015-09-23. Retrieved 2015-05-05.
^ Lekic, V.; Cottaar, S.; Dziewonski, A. & Romanowicz, B. (2012). "Cluster analysis of global lower mantle". Earth and Planetary Science Letters. 357–358. EPSL: 68–77. Bibcode:2012E&PSL.357...68L. doi:10.1016/j.epsl.2012.09.014.
^ ^a ^b Dziewonski, A.M.; Lekic, V.; Romanowicz, B. (2010). "Mantle Anchor Structure: An argument for bottom up tectonics" (PDF). EPSL.^{[permanent dead link‍]}
^ To, A.; Romanowicz, B.; Capdeville, Y.; Takeuchi, N. (2005). "3D effects of sharp boundaries at the borders of the African and Pacific Superplumes: Observation and modeling". Earth and Planetary Science Letters. 233 (1–2). EPSL: 137–153. Bibcode:2005E&PSL.233..137T. doi:10.1016/j.epsl.2005.01.037.
^ ^a ^b McNamara, A.M.; Garnero, E.J.; Rost, S. (2010). "Tracking deep mantle reservoirs with ultra-low velocity zones" (PDF). EPSL. Archived from the original (PDF) on 2021-05-18. Retrieved 2013-06-22.
^ Lau, Harriet C. P.; Mitrovica, Jerry X.; Davis, James L.; Tromp, Jeroen; Yang, Hsin-Ying; Al-Attar, David (15 November 2017). "Tidal tomography constrains Earth's deep-mantle buoyancy". Nature. 551 (7680): 321–326. Bibcode:2017Natur.551..321L. doi:10.1038/nature24452. PMID 29144451. S2CID 4147594. Archived from the original on 11 May 2021. Retrieved 19 July 2019.
^ Jackie Appel (March 31, 2023). "Scientists Are Getting Kinda Anxious About a Pothole in Space". Archived from the original on 2023-04-01. Retrieved 2023-04-01.
^ Campbell, Ian H.; Griffiths, Ross W. (1990). "Implications of mantle plume structure for the evolution of flood basalts". Earth and Planetary Science Letters. 99 (1–2): 79–93. Bibcode:1990E&PSL..99...79C. doi:10.1016/0012-821X(90)90072-6.
^ Davies, D. Rhodri; Goes, S.; Davies, J.H.; Schuberth, B.S.A.; Bunge, H.-P.; Ritsema, J. (November 2012). "Reconciling dynamic and seismic models of Earth's lower mantle: The dominant role of thermal heterogeneity". Earth and Planetary Science Letters. 353–354: 253–269. Bibcode:2012E&PSL.353..253D. doi:10.1016/j.epsl.2012.08.016.
^ ^a ^b Yuan, Qian; Li, Mingming; Desch, Steven J.; Ko, Byeongkwan; Deng, Hongping; Garnero, Edward J.; Gabriel, Travis S. J.; Kegerreis, Jacob A.; Miyazaki, Yoshinori; Eke, Vincent; Asimow, Paul D. (November 2023). "Moon-forming impactor as a source of Earth's basal mantle anomalies". Nature. 623 (7985): 95–99. Bibcode:2023Natur.623...95Y. doi:10.1038/s41586-023-06589-1. ISSN 1476-4687. PMID 37914947. S2CID 264869152.
^ Yuan, Qian; Li, Mingming; Desch, Steven J.; Ko, Byeongkwan (2021). "Giant impact origin for the large low shear velocity provinces" (PDF). 52nd Lunar and Planetary Science Conference. Archived (PDF) from the original on 24 March 2021. Retrieved 27 March 2021.
^ Zaria Gorvett (12 May 2022). "Why are there continent-sized 'blobs' in the deep Earth?". BBC Future. Archived from the original on 21 May 2022. Retrieved 21 May 2022.
^ Steinberger, B.; Torsvik, T.H. (2012). "A geodynamic model of plumes from the margins of Large Low Shear Velocity Provinces" (PDF). G^3. Archived (PDF) from the original on 2014-08-15. Retrieved 2013-06-22.

External links

Garnero, E. (21–23 March 2013). Possible reservoirs of radioactivity in the deep mantle (PDF). Neutrino Geoscience 2013. Takayama, Japan.
McNamara, A. K. (5 June 2019). "A review of large low shear velocity provinces and ultra low velocity zones". Tectonophysics. 760: 199–220. Bibcode:2019Tectp.760..199M. doi:10.1016/j.tecto.2018.04.015. S2CID 134501105.
Andrews, R. G. (7 May 2022). "What are the mysterious continent-sized lumps deep inside Earth?". New Scientist (3385).

[:0-1] Cottaar; Lekic (2016). "Morphology of lower mantle structures". Geophysical Journal International. 207 (2): 1122–1136. Bibcode:2016GeoJI.207.1122C. doi:10.1093/gji/ggw324.

[2] Garnero, Edward J.; McNamara, Allen K.; Shim, Sang-Heon (2016). "Continent-sized anomalous zones with low seismic velocity at the base of Earth's mantle". Nature Geoscience. 9 (7): 481–489. Bibcode:2016NatGe...9..481G. doi:10.1038/ngeo2733.

[3] Lau, Harriet; Al-Attar, David (2021-12-01). "Weighing TUZO and JASON individually". AGU Fall Meeting Abstracts. 2021: DI13A–05. Bibcode:2021AGUFMDI13A..05L.

[MantleD-4] Maruyama; Santosh; Zhao (January 2007). "Superplume, supercontinent, and post-perovskite: Mantle dynamis and anti-plate tectonics on the Core-Mantle Boundary". Gondwana Research. 11 (1–2): 7–37. Bibcode:2007GondR..11....7M. doi:10.1016/j.gr.2006.06.003.

[5] Davies, D. R.; Goes, S.; Lau, H. C. P. (2015), Khan, Amir; Deschamps, Frédéric (eds.), "Thermally Dominated Deep Mantle LLSVPs: A Review", The Earth's Heterogeneous Mantle: A Geophysical, Geodynamical, and Geochemical Perspective, Cham: Springer International Publishing, pp. 441–477, doi:10.1007/978-3-319-15627-9_14, ISBN 978-3-319-15627-9, retrieved 2024-04-09

[Peltier-6] Peltier, W.R. (2007). "Mantle dynamics and the D″ layer implications of the post-perovskite phase" (PDF). In Kei Hirose; John Brodholt; Thome Lay; David Yuen (eds.). Post-Perovskite: The Last Mantle Phase Transition. AGU Geophysical Monographs. Vol. 174. American Geophysical Union. pp. 217–227. ISBN 978-0-87590-439-9. Archived (PDF) from the original on 2015-09-23. Retrieved 2015-05-05.

[Lekic2012-7] Lekic, V.; Cottaar, S.; Dziewonski, A. & Romanowicz, B. (2012). "Cluster analysis of global lower mantle". Earth and Planetary Science Letters. 357–358. EPSL: 68–77. Bibcode:2012E&PSL.357...68L. doi:10.1016/j.epsl.2012.09.014.

[Dziewonski2010-8] Dziewonski, A.M.; Lekic, V.; Romanowicz, B. (2010). "Mantle Anchor Structure: An argument for bottom up tectonics" (PDF). EPSL.^{[permanent dead link‍]}

[To2005-9] To, A.; Romanowicz, B.; Capdeville, Y.; Takeuchi, N. (2005). "3D effects of sharp boundaries at the borders of the African and Pacific Superplumes: Observation and modeling". Earth and Planetary Science Letters. 233 (1–2). EPSL: 137–153. Bibcode:2005E&PSL.233..137T. doi:10.1016/j.epsl.2005.01.037.

[McNamara2010-10] McNamara, A.M.; Garnero, E.J.; Rost, S. (2010). "Tracking deep mantle reservoirs with ultra-low velocity zones" (PDF). EPSL. Archived from the original (PDF) on 2021-05-18. Retrieved 2013-06-22.

[11] Lau, Harriet C. P.; Mitrovica, Jerry X.; Davis, James L.; Tromp, Jeroen; Yang, Hsin-Ying; Al-Attar, David (15 November 2017). "Tidal tomography constrains Earth's deep-mantle buoyancy". Nature. 551 (7680): 321–326. Bibcode:2017Natur.551..321L. doi:10.1038/nature24452. PMID 29144451. S2CID 4147594. Archived from the original on 11 May 2021. Retrieved 19 July 2019.

[12] Jackie Appel (March 31, 2023). "Scientists Are Getting Kinda Anxious About a Pothole in Space". Archived from the original on 2023-04-01. Retrieved 2023-04-01.

[13] Campbell, Ian H.; Griffiths, Ross W. (1990). "Implications of mantle plume structure for the evolution of flood basalts". Earth and Planetary Science Letters. 99 (1–2): 79–93. Bibcode:1990E&PSL..99...79C. doi:10.1016/0012-821X(90)90072-6.

[14] Davies, D. Rhodri; Goes, S.; Davies, J.H.; Schuberth, B.S.A.; Bunge, H.-P.; Ritsema, J. (November 2012). "Reconciling dynamic and seismic models of Earth's lower mantle: The dominant role of thermal heterogeneity". Earth and Planetary Science Letters. 353–354: 253–269. Bibcode:2012E&PSL.353..253D. doi:10.1016/j.epsl.2012.08.016.

[:1-15] Yuan, Qian; Li, Mingming; Desch, Steven J.; Ko, Byeongkwan; Deng, Hongping; Garnero, Edward J.; Gabriel, Travis S. J.; Kegerreis, Jacob A.; Miyazaki, Yoshinori; Eke, Vincent; Asimow, Paul D. (November 2023). "Moon-forming impactor as a source of Earth's basal mantle anomalies". Nature. 623 (7985): 95–99. Bibcode:2023Natur.623...95Y. doi:10.1038/s41586-023-06589-1. ISSN 1476-4687. PMID 37914947. S2CID 264869152.

[16] Yuan, Qian; Li, Mingming; Desch, Steven J.; Ko, Byeongkwan (2021). "Giant impact origin for the large low shear velocity provinces" (PDF). 52nd Lunar and Planetary Science Conference. Archived (PDF) from the original on 24 March 2021. Retrieved 27 March 2021.

[17] Zaria Gorvett (12 May 2022). "Why are there continent-sized 'blobs' in the deep Earth?". BBC Future. Archived from the original on 21 May 2022. Retrieved 21 May 2022.

[Steinberger2012-18] Steinberger, B.; Torsvik, T.H. (2012). "A geodynamic model of plumes from the margins of Large Low Shear Velocity Provinces" (PDF). G^3. Archived (PDF) from the original on 2014-08-15. Retrieved 2013-06-22.

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@@ Line 1: / Line 1: @@
 {{Short description|Structures of the Earth's mantle}}
-[[File:LLSVP.gif|thumb|381x381px|Animation showing LLSVPs as inferred using [[seismic tomography]]<ref name=":0">{{Cite journal|last1=Cottaar|last2=Lekic|date=2016|title=Morphology of lower mantle structures|journal=Geophysical Journal International|volume=207|issue=2|pages=1122–1136|bibcode=2016GeoJI.207.1122C|doi=10.1093/gji/ggw324|doi-access=free}}</ref>]]
+[[File:LLSVP.gif|thumb|381x381px|Animation showing LLSVPs as inferred using [[seismic tomography]]<ref name=":0">{{Cite journal |last1=Cottaar |last2=Lekic |date=2016 |title=Morphology of lower mantle structures |journal=[[Geophysical Journal International]] |volume=207 |issue=2 |pages=1122–1136 |bibcode=2016GeoJI.207.1122C |doi=10.1093/gji/ggw324 |doi-access=free}}</ref>]]
-'''Large low-shear-velocity provinces''', '''LLSVPs''', also called '''LLVPs''' or '''superplumes''', are characteristic structures of parts of the lowermost [[mantle (geology)|mantle]] (the region surrounding the [[Earth's outer core|outer core]]) of Earth.<ref>{{Cite journal|last=Garnero, McNamara, Shim|date=2016|title=Continent-sized anomalous zones with low seismic velocity at the base of Earth's mantle|journal=Nature Geoscience|volume=9|issue=7|pages=481–489|bibcode=2016NatGe...9..481G|doi=10.1038/ngeo2733}}</ref> These provinces are characterized by slow [[S-wave|shear wave]] velocities and were discovered by [[seismic tomography]] of deep Earth. There are two main provinces: the African LLSVP and the Pacific LLSVP. Both extend laterally for thousands of kilometers and possibly up to 1,000 km vertically from the [[core–mantle boundary]]. The Pacific LLSVP is 3,000 km across, and underlies four [[Hotspot (geology)|hotspots]] that suggest multiple [[Mantle plume|mantle plumes]] underneath.<ref name="MantleD">{{cite journal|last1=Maruyama|last2=Santosh|last3=Zhao|title=Superplume, supercontinent, and post-perovskite: Mantle dynamis and anti-plate tectonics on the Core-Mantle Boundary|journal=Gondwana Research|date=4 June 2006|volume=11|issue=1–2|pages=7–37|access-date=17 August 2006| url=https://www.researchgate.net/publication/223376499|doi=10.1016/j.gr.2006.06.003|bibcode=2007GondR..11....7M}}</ref>  These zones represent around 8% of the volume of the mantle (6% of Earth).<ref name=":0" /> Other names for LLSVPs include "[[Superswell|superswells]]<!--Do they (whoever added this word to the article) mean "superswells"?-->", "thermo-chemical piles", or "hidden reservoirs". Most of these names, however, are more interpretive of their proposed [[geodynamics|geodynamical]] or [[geochemistry|geochemical]] effects. For example, the name "thermo-chemical pile" interprets LLSVPs as lower-mantle piles of thermally hot and/or chemically distinct material. LLSVPs are still relatively mysterious, and many questions remain about their nature, origin, and geodynamic effects.
+'''Large low-shear-velocity provinces''' ('''LLSVPs'''), also called '''large low-velocity provinces''' ('''LLVPs''') or '''superplumes''', are characteristic structures of parts of the lowermost [[Earth's mantle|mantle]], the region surrounding the [[Earth's outer core|outer core]] deep inside the Earth.<ref>{{Cite journal |last1=Garnero |first1=Edward J. |last2=McNamara |first2=Allen K. |last3=Shim |first3=Sang-Heon |date=2016 |title=Continent-sized anomalous zones with low seismic velocity at the base of Earth's mantle |journal=[[Nature Geoscience]] |volume=9 |issue=7 |pages=481–489 |bibcode=2016NatGe...9..481G |doi=10.1038/ngeo2733}}</ref> These provinces are characterized by slow [[S-wave|shear wave]] velocities and were discovered by [[seismic tomography]] of deep Earth. There are two main provinces: the '''African LLSVP''' and the '''Pacific LLSVP''', both extending laterally for thousands of kilometers and possibly up to 1,000 kilometres vertically from the [[core–mantle boundary]]. These have been named '''Tuzo''' and '''Jason''' respectively, after [[Tuzo Wilson]] and [[W. Jason Morgan]], two geologists acclaimed in the field of plate tectonics.<ref>{{Cite journal |last1=Lau |first1=Harriet |last2=Al-Attar |first2=David |date=2021-12-01 |title=Weighing TUZO and JASON individually |journal=AGU Fall Meeting Abstracts |url=https://ui.adsabs.harvard.edu/abs/2021AGUFMDI13A..05L |volume=2021 |pages=DI13A–05|bibcode=2021AGUFMDI13A..05L }}</ref> The Pacific LLSVP is {{Convert|3,000|km|mi|abbr=off|sp=us}} across and underlies four [[Hotspot (geology)|hotspots]] on Earth's [[Crust (geology)|crust]] that suggest multiple [[mantle plume]]s underneath.<ref name="MantleD">{{cite journal |last1=Maruyama |last2=Santosh |last3=Zhao |date=January 2007 |title=Superplume, supercontinent, and post-perovskite: Mantle dynamis and anti-plate tectonics on the Core-Mantle Boundary |journal=[[Gondwana Research]] |volume=11 |issue=1–2 |pages=7–37 |bibcode=2007GondR..11....7M |doi=10.1016/j.gr.2006.06.003}}</ref> These zones represent around 8% of the volume of the mantle, or 6% of the entire Earth.<ref name=":0" />
+Other names for LLSVPs and their superstructures include [[superswell]]s, superplumes, thermo-chemical piles, or hidden reservoirs, mostly describing their proposed [[geodynamics|geodynamical]] or [[geochemistry|geochemical]] effects. For example, the name "thermo-chemical pile" interprets LLSVPs as lower-mantle piles of thermally hot and/or chemically distinct material. LLSVPs are still relatively mysterious, and many questions remain about their nature, origin, and geodynamic effects.<ref>{{Citation |last1=Davies |first1=D. R. |title=Thermally Dominated Deep Mantle LLSVPs: A Review |date=2015 |work=The Earth's Heterogeneous Mantle: A Geophysical, Geodynamical, and Geochemical Perspective |pages=441–477 |editor-last=Khan |editor-first=Amir |url=https://doi.org/10.1007/978-3-319-15627-9_14 |access-date=2024-04-09 |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-319-15627-9_14 |isbn=978-3-319-15627-9 |last2=Goes |first2=S. |last3=Lau |first3=H. C. P. |editor2-last=Deschamps |editor2-first=Frédéric}}</ref>
-==Seismological constraints==
-LLSVPs were discovered in full mantle seismic tomographic models of [[shear velocity]] as slow features in the lowermost mantle beneath Africa and the Pacific. The boundaries of these features appear fairly consistent across models when applying objective [[k-means clustering]].<ref name="Lekic2012">{{cite journal|title= Cluster analysis of global lower mantle
+==Seismological modeling==
-|author= Lekic, V.
+Directly above the [[core–mantle boundary]] is a {{Convert|200|km|mi|abbr=off|sp=us}} thick layer of the lower mantle. This layer is known as the D″ ("D double-prime" or "D prime prime") or degree two structure.<ref name="Peltier">{{cite book |author=Peltier, W.R. |title=Post-Perovskite: The Last Mantle Phase Transition |date=2007 |publisher=[[American Geophysical Union]] |isbn=978-0-87590-439-9 |editor=Kei Hirose |series=AGU Geophysical Monographs |volume=174 |pages=217–227 |chapter=Mantle dynamics and the D″ layer implications of the post-perovskite phase |access-date=2015-05-05 |editor2=John Brodholt |editor3=Thome Lay |editor4=David Yuen |chapter-url=http://www.atmosp.physics.utoronto.ca/~peltier/pubs_books/W.R.%20Peltier,%20Mantle%20Dynamics%20and%20the%20D%20doubleprime%20Layer.Implications%20of%20the%20Post-perovskite%20Phase,%20AGU%20Geodynamics%20Series%20Monograph,%20AGU%20Books,%20pages%20217-227,%202007.pdf |archive-url=https://web.archive.org/web/20150923175914/http://www.atmosp.physics.utoronto.ca/~peltier/pubs_books/W.R.%20Peltier,%20Mantle%20Dynamics%20and%20the%20D%20doubleprime%20Layer.Implications%20of%20the%20Post-perovskite%20Phase,%20AGU%20Geodynamics%20Series%20Monograph,%20AGU%20Books,%20pages%20217-227,%202007.pdf |archive-date=2015-09-23 |url-status=live}}</ref> LLSVPs were discovered in full mantle seismic [[Tomography|tomographic]] models of [[shear velocity]] as slow features at the D″ layer beneath Africa and the Pacific.<ref name="Lekic2012">{{cite journal |author=Lekic, V. |author2=Cottaar, S. |author3=Dziewonski, A. |author4=Romanowicz, B. |name-list-style=amp |date=2012 |title=Cluster analysis of global lower mantle |journal=[[Earth and Planetary Science Letters]] |publisher=EPSL |volume=357-358 |pages=68–77 |bibcode=2012E&PSL.357...68L |doi=10.1016/j.epsl.2012.09.014}}</ref> The global [[spherical harmonics]] of the D″ layer are stable throughout most of the mantle but anomalies appear along the two LLSVPs. By using shear wave velocities, the locations of the LLSVPs can be verified, and a stable pattern for [[mantle convection]] emerges. This stable configuration is responsible for the geometry of [[Plate tectonics|plate motions]] at the surface.<ref name="Dziewonski2010">{{cite web
-|author2= Cottaar, S.
+|url=ftp://quake.geo.berkeley.edu/outgoing/barbara/REPRINTS/dziewonski-epsl2010.pdf
-|author3= Dziewonski, A.
-|author4= Romanowicz, B.
-|name-list-style= amp
-|date=2012
-|publisher=EPSL
- |doi=10.1016/j.epsl.2012.09.014
- |bibcode=2012E&PSL.357...68L
- |volume=357-358
- |journal=Earth and Planetary Science Letters
- |pages=68–77
-}}</ref> The global [[spherical harmonic]] degree two structure is strong and aligns with its smallest moments of inertia along with the two LLSVPs. This means, by using shear wave velocities, the established locations of the LLSVPs are not only verified, a stable pattern for mantle convection emerges. This stable configuration is responsible for the geometry of plate motions at the surface due as well as mantle convection.<ref name="Dziewonski2010">{{cite web|url=ftp://quake.geo.berkeley.edu/outgoing/barbara/REPRINTS/dziewonski-epsl2010.pdf
 |title=Mantle Anchor Structure: An argument for bottom up tectonics
 |author=Dziewonski, A.M.
@@ Line 24: / Line 14: @@
 |date=2010
 |publisher=EPSL
+}}{{Dead link|date=February 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
-}}</ref> Another name for the degree two structure, a roughly 200&nbsp;km thick layer of the lower mantle directly above the [[core–mantle boundary]] (CMB), is the D″ ("D double-prime" or "D prime prime").<ref name="Peltier">{{cite book|chapter-url=http://www.atmosp.physics.utoronto.ca/~peltier/pubs_books/W.R.%20Peltier,%20Mantle%20Dynamics%20and%20the%20D%20doubleprime%20Layer.Implications%20of%20the%20Post-perovskite%20Phase,%20AGU%20Geodynamics%20Series%20Monograph,%20AGU%20Books,%20pages%20217-227,%202007.pdf|title=Post-Perovskite: The Last Mantle Phase Transition; ''Volume 174 in AGU Geophysical Monographs''|date=2007|publisher=[[American Geophysical Union]]|isbn=978-0-87590-439-9|pages=217–227|chapter=Mantle dynamics and the D'' layer implications of the post-perovskite phase|author=WR Peltier|editor=Kei Hirose|editor2=John Brodholt|editor3=Thome Lay|editor4=David Yuen}}</ref> The LLSVPs lie around the equator, but mostly on the southern hemisphere. Global tomography models inherently result in smooth features; local waveform modeling of [[seismic wave|body waves]], however, has shown that the LLSVPs have sharp boundaries.<ref name="To2005">{{cite journal|title= 3D effects of sharp boundaries at the borders of the African and Pacific Superplumes: Observation and modeling
+The LLSVPs lie around the equator, but mostly on the Southern Hemisphere. Global tomography models inherently result in smooth features; local waveform modeling of [[seismic wave|body waves]], however, has shown that the LLSVPs have sharp boundaries.<ref name="To2005">{{cite journal|title= 3D effects of sharp boundaries at the borders of the African and Pacific Superplumes: Observation and modeling
 |author= To, A.
 |author2= Romanowicz, B.
@@ Line 37: / Line 29: @@
  |journal=Earth and Planetary Science Letters
  |pages=137–153
+}}</ref> The sharpness of the boundaries makes it difficult to explain the features by temperature alone; the LLSVPs need to be compositionally distinct to explain the velocity jump. [[Ultra-low velocity zone]]s at smaller scales have been discovered mainly at the edges of these LLSVPs.<ref name="McNamara2010">{{cite web
-}}</ref>
+|url= http://mcnamara.asu.edu/content/publications/pdfs/McNamara_et_al_epsl_2010.pdf
-The sharpness of the boundaries makes it difficult to explain the features by temperature alone; the LLSVPs need to be compositionally distinct to explain the velocity jump.
-[[Ultra low velocity zone]]s (ULVZ) at smaller scales have been discovered mainly at the edges of these LLSVPs.<ref name="McNamara2010">{{cite web|url=http://mcnamara.asu.edu/content/publications/pdfs/McNamara_et_al_epsl_2010.pdf |title= Tracking deep mantle reservoirs with ultra-low velocity zones
+|title= Tracking deep mantle reservoirs with ultra-low velocity zones
 |author= McNamara, A.M.
 |author2= Garnero, E.J.
 |author3= Rost, S.
-|date=2010
+|date= 2010
-|publisher=EPSL
+|publisher= EPSL
+|access-date= 2013-06-22
+|archive-date= 2021-05-18
+|archive-url= https://web.archive.org/web/20210518114452/http://mcnamara.asu.edu/content/publications/pdfs/McNamara_et_al_epsl_2010.pdf
+|url-status= dead
 }}</ref>
-By using the solid Earth tide, the density of these regions has been determined. The bottom two thirds are 0.5% denser than the bulk of the mantle. However tidal tomography cannot say exactly how the excess mass is distributed. The overdensity may be due to primordial material or subducted ocean slabs.<ref>{{cite journal|last1=Lau|first1=Harriet C. P.|author-link2=Jerry X. Mitrovica|last2=Mitrovica|first2=Jerry X.|last3=Davis|first3=James L.|last4=Tromp|first4=Jeroen|last5=Yang|first5=Hsin-Ying|last6=Al-Attar|first6=David|title=Tidal tomography constrains Earth's deep-mantle buoyancy|journal=Nature|date=15 November 2017|volume=551|issue=7680|pages=321–326|doi=10.1038/nature24452|pmid=29144451|bibcode=2017Natur.551..321L|s2cid=4147594|url=https://www.repository.cam.ac.uk/handle/1810/288623}}<!--https://www.repository.cam.ac.uk/handle/1810/288623}}--></ref>
+By using the solid [[Earth tide]], the density of these regions has been determined. The bottom two thirds are 0.5% denser than the bulk of the mantle. However, tidal tomography cannot determine how the excess mass is distributed; the higher density may be caused by primordial material or [[Subduction|subducted]] ocean slabs.<ref>{{cite journal |last1=Lau |first1=Harriet C. P. |author-link2=Jerry X. Mitrovica |last2=Mitrovica |first2=Jerry X. |last3=Davis |first3=James L. |last4=Tromp |first4=Jeroen |last5=Yang |first5=Hsin-Ying |last6=Al-Attar |first6=David |title=Tidal tomography constrains Earth's deep-mantle buoyancy |journal=Nature |date=15 November 2017 |volume=551 |issue=7680 |pages=321–326 |doi=10.1038/nature24452 |pmid=29144451 |bibcode=2017Natur.551..321L |s2cid=4147594 |url=https://www.repository.cam.ac.uk/handle/1810/288623 |access-date=19 July 2019 |archive-date=11 May 2021 |archive-url=https://web.archive.org/web/20210511192559/https://www.repository.cam.ac.uk/handle/1810/288623 |url-status=live }}</ref> The African LLSVP may be a potential cause for the [[South Atlantic Anomaly]].<ref>{{Cite web |author=Jackie Appel |date=March 31, 2023 |title=Scientists Are Getting Kinda Anxious About a Pothole in Space |url=https://www.popularmechanics.com/space/satellites/a43412493/nasa-tracking-dent-in-earths-magnetic-field/ |url-status=live |archive-url=https://web.archive.org/web/20230401004417/https://www.popularmechanics.com/space/satellites/a43412493/nasa-tracking-dent-in-earths-magnetic-field/ |archive-date=2023-04-01 |access-date=2023-04-01}}</ref>
-==Possible origin==
+==Origins==
-Several hypotheses have been proposed for the origin and persistence of LLSVPs, depending on whether the provinces represent purely thermal unconformities (i.e. are isochemical in nature, of the same chemical composition as the surrounding mantle) or represent chemical unconformities as well (i.e. are thermochemical in nature, of different chemical composition from the surrounding mantle).
+Several hypotheses have been proposed for the origin and persistence of LLSVPs, depending on whether the provinces represent purely thermal [[Unconformity|unconformities]] (i.e. are isochemical in nature, of the same chemical composition as the surrounding mantle) or represent chemical unconformities as well (i.e. are [[Thermochemistry|thermochemical]] in nature, of different chemical composition from the surrounding mantle). If LLSVPs represent purely thermal unconformities, then they may have formed as large [[mantle plume]]s of hot, upwelling mantle. However, [[Geodynamics|geodynamical]] studies predict that isochemical upwelling of a hotter, lower viscosity material should produce long, narrow plumes,<ref>{{Cite journal |last1=Campbell |first1=Ian H. |last2=Griffiths |first2=Ross W. |date=1990 |title=Implications of mantle plume structure for the evolution of flood basalts |journal=[[Earth and Planetary Science Letters]] |volume=99 |issue=1–2 |pages=79–93 |doi=10.1016/0012-821X(90)90072-6 |bibcode=1990E&PSL..99...79C}}</ref> unlike the large, wide plumes seen in LLSVPs. It is important to remember, however, that the resolution of geodynamical models and seismic images of Earth's mantle are very different.<ref>{{Cite journal |last1=Davies |first1=D. Rhodri |last2=Goes |first2=S. |last3=Davies |first3=J.H. |last4=Schuberth |first4=B.S.A. |last5=Bunge |first5=H.-P. |last6=Ritsema |first6=J. |date=November 2012 |title=Reconciling dynamic and seismic models of Earth's lower mantle: The dominant role of thermal heterogeneity |url=https://linkinghub.elsevier.com/retrieve/pii/S0012821X1200444X |journal=Earth and Planetary Science Letters |language=en |volume=353-354 |pages=253–269 |doi=10.1016/j.epsl.2012.08.016|bibcode=2012E&PSL.353..253D }}</ref>
+The current leading hypothesis for the LLSVPs is the accumulation of subducted oceanic slabs. This corresponds with the locations of known [[Crustal recycling#Historical and theoretical context|slab graveyards]] surrounding the Pacific LLSVP. These graveyards are thought to be the reason for the high velocity zone anomalies surrounding the Pacific LLSVP and are thought to have formed by subduction zones that were around long before the dispersion—some 750 million years ago—of the supercontinent [[Rodinia]]. Aided by the [[Phase transition|phase transformation]], the temperature would partially melt the slabs to form a dense melt that pools and forms the ultra-low velocity zone structures at the bottom of the core-mantle boundary closer to the LLSVP than the slab graveyards. The rest of the material is then carried upwards via chemical-induced buoyancy and contributes to the high levels of basalt found at the [[mid-ocean ridge]]. The resulting motion forms small clusters of small plumes right above the core-mantle boundary that combine to form larger plumes and then contribute to superplumes. The Pacific and African LLSVP, in this scenario, are originally created by a discharge of heat from the core (4000&nbsp;K) to the much colder mantle (2000&nbsp;K); the recycled [[lithosphere]] is fuel that helps drive the superplume convection. Since it would be difficult for the Earth's core to maintain this high heat by itself, it gives support for the existence of [[radiogenic nuclide]]s in the core, as well as the indication that if fertile subducted lithosphere stops subducting in locations preferable for superplume consumption, it will mark the demise of that superplume.<ref name="MantleD" />
-If LLSVPs represent purely thermal unconformities, then they may have formed as [[Mantle plume|megaplumes]] of hot, upwelling mantle. However, [[Geodynamics|geodynamical]] studies predict that isochemical upwelling of a hotter, lower viscosity material should produce long, narrow plumes,<ref>{{Cite journal |last=Campbell |first=Ian H., & Griffiths, Ross W. |date=1990 |title=Implications of mantle plume structure for the evolution of flood basalts |url=https://pdf.sciencedirectassets.com/271830/1-s2.0-S0012821X00X03664/1-s2.0-0012821X90900726/main.pdf?X-Amz-Security-Token=IQoJb3JpZ2luX2VjEOL%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaCXVzLWVhc3QtMSJHMEUCIFWyCNNNh0Eiucm3RfQz1D8vu3kOjXdK0LGiNZBLe3SbAiEA%2Fg8nnF5zhao5SQ%2F9DeFIEr%2FoNrpscrpDPmsVPGI7YeEq%2BgMISxAEGgwwNTkwMDM1NDY4NjUiDOQpI34C3RWhV248dyrXA1xgVZ3LMyBO66OOGRYa0cqf8Y5UwbdvFpNTLV3cUeEV3%2B8MK152RQCr5JFhrSaYAHVCPb8Rh8Sxt7UgIbHURDdSfOJlkVYhO4QD6oDZWaD1quVZDPbTQEqjPAKsgPHWpumi5bJCwhBrpBvyKyrVs8tbieJxuJ4lnB%2FoiHSgnh0DmmA7uOWVKb%2Bjkwin1SdcdfWdHYOelmhyZBGLtQ7V9iz6wcQ6MDw0ROc7Avhl0q7ssT3D%2BzHEOFyQLcWDUfPhnguJ7OdIBGYaAydIWY5945NUCLj8ov04dcyY1KJyD6twWAjcAd2Zk9PIByU%2BGQapGtr2M%2Fxmv%2F%2Brwu4oA0%2FREhJIqLJwsajuqPp0uKLol2yC7%2Fb0mOo00%2FZsp2erLpixjgx5gVc4aNro%2BxXSm4jg8V1psv8fVfohaVy%2B95AstEmAcgCpg5aj4tetu9so3T4vritzEhI5ADJaGZwtoSsD0NXasBOWMkjgWCli2%2FAA%2BgIUouD9%2B1VSAcpX9%2BFccMNEkOB9JA15ZEsN3oGhFBDRYGLujhOeY6IF8vs5od%2Bqrk4sfKgPZc1K2wEyt9xPsUSt81O%2FUgao84QtsO5WrKUaYEEnAJNichBGqI9LMRsCyK1S4kReAMeLkzDD%2BYORBjqlASGeHf%2B5bcYM1km4zTtUL1jirRIHnsGaL3n%2Bmppeh156AuQpuK3Yw%2FZ8QC18jDy2j%2BxEsLYYHpEf2x7Vtk1ng2vUfI98VKlUHaKVK049XvsgR6s7dl9XWW04J4hNajUh8G5v094Mf%2FhERSvIGYNDY9bnXSMdmH0guz9jOzWFq2FSoBiGfR9%2FiDyOib%2FEWpWNtvj4GMz0DlREteIZ42Fw8zVhc2LMFA%3D%3D&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20220303T183218Z&X-Amz-SignedHeaders=host&X-Amz-Expires=300&X-Amz-Credential=ASIAQ3PHCVTYYMXZUOU7%2F20220303%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Signature=3dad7ef8890242b27dcb71282e292ef93e5c108a61c273591e8c1844fdf85ec4&hash=15fa8688f42db0b0702a8caf258a734d97d8f6254355efe6c1da6ab45c0ee1b0&host=68042c943591013ac2b2430a89b270f6af2c76d8dfd086a07176afe7c76c2c61&pii=0012821X90900726&tid=spdf-467f7f96-4382-48fd-92ee-95ad34246574&sid=631d5fef174f004e616ac9328c71de843c92gxrqa&type=client&ua=5704565a5753560352&rr=6e64743c0aad7d7d |journal=[[Earth and Planetary Science Letters]] |volume=99 |pages=79-93 |via=Elsevier Science Direct}}</ref>  unlike the large, wide plumes we observe in LLSVPs.
+Another proposed origin for the LLSVPs is that their formation is related to the [[giant-impact hypothesis]], which states that the [[Moon]] formed after the Earth collided with a planet-sized body called [[Theia (planet)|Theia]].<ref name=":1">{{Cite journal |last1=Yuan |first1=Qian |last2=Li |first2=Mingming |last3=Desch |first3=Steven J. |last4=Ko |first4=Byeongkwan |last5=Deng |first5=Hongping |last6=Garnero |first6=Edward J. |last7=Gabriel |first7=Travis S. J. |last8=Kegerreis |first8=Jacob A. |last9=Miyazaki |first9=Yoshinori |last10=Eke |first10=Vincent |last11=Asimow |first11=Paul D. |date=November 2023 |title=Moon-forming impactor as a source of Earth's basal mantle anomalies |journal=Nature |volume=623 |issue=7985 |pages=95–99 |doi=10.1038/s41586-023-06589-1 |pmid=37914947 |bibcode=2023Natur.623...95Y |s2cid=264869152 |issn=1476-4687 |language=en}}</ref> The hypothesis suggests that the LLSVPs may represent fragments of Theia's mantle which sank through to Earth's core-mantle boundary.<ref name=":1" /> The higher density of the mantle fragments is due to their enrichment in [[iron(II) oxide]] with respect to the rest of Earth's mantle. This higher iron(II) oxide composition would also be consistent with the isotope geochemistry of lunar samples, as well as that of the [[ocean island basalt]]s overlying the LLSVPs.<ref>{{cite journal |last1=Yuan |first1=Qian |last2=Li |first2=Mingming |last3=Desch |first3=Steven J. |last4=Ko |first4=Byeongkwan |title=Giant impact origin for the large low shear velocity provinces |url=https://www.hou.usra.edu/meetings/lpsc2021/pdf/1980.pdf |journal=52nd Lunar and Planetary Science Conference |date=2021 |access-date=27 March 2021 |archive-date=24 March 2021 |archive-url=https://web.archive.org/web/20210324204531/https://www.hou.usra.edu/meetings/lpsc2021/pdf/1980.pdf |url-status=live }}</ref><ref>{{cite web |url=https://www.bbc.com/future/article/20220510-why-are-there-continent-sized-blobs-in-the-deep-earth |title=Why are there continent-sized 'blobs' in the deep Earth? |work=[[BBC Future]] |author=Zaria Gorvett |date=12 May 2022 |access-date=21 May 2022 |archive-date=21 May 2022 |archive-url=https://web.archive.org/web/20220521105154/https://www.bbc.com/future/article/20220510-why-are-there-continent-sized-blobs-in-the-deep-earth |url-status=live }}</ref>
-The current leading hypothesis for the LLSVPs is the accumulation of subducted oceanic slabs. This corresponds with the locations of known [[Crustal_recycling#Historical_and_theoretical_context|slab graveyards]] surrounding the Pacific LLSVP. These graveyards are thought to be the reason for the high velocity zone anomalies surrounding the Pacific LLSVP and are thought to have formed by subduction zones that were around long before the dispersion—some 750 million years ago—of the supercontinent [[Rodinia]]. Aided by the phase transformation, the temperature would partially melt the slabs, to form a dense heavy melt that pools and forms the [[ultra low velocity zone]] (ULVZ) structures at the bottom of the core-mantle boundary closer to the LLSVP than the slab graveyards. The rest of the material is then carried upwards due to chemical-induced buoyancy and contributes to the high levels of basalt found at the [[mid-ocean ridge]]. The resulting motion forms small clusters of small plumes right above the core-mantle boundary that combine to form larger plumes and then contribute to superplumes. The Pacific and African LLSVP, in this scenario, are originally created by a discharge of heat from the core (4000&nbsp;K) to the much colder mantle (2000&nbsp;K), the recycled lithosphere is only fuel that helps drive the superplume convection. Since it would be difficult for the Earth's core to maintain this high heat by itself, it gives support for the existence of [[radiogenic nuclide]]s in the core, as well as the indication that if fertile subducted lithosphere stops subducting in locations preferable for superplume consumption, it will mark the demise of that superplume.<ref name="MantleD" />
-A second proposed origin for the LLSVPs is that their formation is related to the [[giant-impact hypothesis]], which states that the [[Moon]] formed after the Earth collided with a planet-sized body called [[Theia (planet)|Theia]]. The hypothesis suggests that the LLSVPs are fragments of Theia's mantle which sank through to Earth's core-mantle boundary. The higher density of the mantle fragments is due to their enrichment in [[iron(II) oxide]] with respect to the rest of Earth's mantle. This higher iron(II) oxide composition would also be consistent with the isotope geochemistry of lunar samples as well as that of the oceanic island basalts overlying the LLSVPs.<ref>{{cite journal |last1=Yuan |first1=Qian |last2=Li |first2=Mingming |last3=Desch |first3=Steven J. |last4=Ko |first4=Byeongkwan |title=Giant impact origin for the large low shear velocity provinces |journal=52nd Lunar and Planetary Science Conference |date=2021 |url=https://www.hou.usra.edu/meetings/lpsc2021/pdf/1980.pdf |access-date=27 March 2021}}</ref><ref>[https://www.bbc.com/future/article/20220510-why-are-there-continent-sized-blobs-in-the-deep-earth Why are there continent-sized 'blobs' in the deep Earth?], BBC Future, by Zaria Gorvett, 12 May 2022</ref>
 ==Dynamics==
-Geodynamic [[mantle convection]] models have included compositional distinctive material. The material tends to get swept up in ridges or piles.<ref name="McNamara2010" /> When including realistic past [[plate tectonics|plate motions]] into the modeling, the material gets swept up in locations that are remarkably similar to the present day location of the LLSVPs.<ref name="Steinberger2012">{{cite web|url=http://www.earthdynamics.org/papers-ED/2012/2012-Steinberger-Torsvik-G3.pdf
+Geodynamic mantle convection models have included compositional distinctive material. The material tends to get swept up in ridges or piles.<ref name="McNamara2010" /> When including realistic past plate motions into the modeling, the material gets swept up in locations that are remarkably similar to the present day location of the LLSVPs.<ref name="Steinberger2012">{{cite web
+|url=http://www.earthdynamics.org/papers-ED/2012/2012-Steinberger-Torsvik-G3.pdf
 |title=A geodynamic model of plumes from the margins of Large Low Shear Velocity Provinces
 |author=Steinberger, B.
 |author2=Torsvik, T.H.
 |date=2012
+|publisher=G^3
-|publisher=G^3 }}</ref> These locations also correspond with known [[Slab (geology)|slab]] graveyard locations mentioned in the origin section. These types of models, as well as the observation that the degree two structure of the LLSVPs is orthogonal to the path of [[true polar wander]], suggest these mantle structures have been stable over large amounts of time. This geometrical relationship is also consistent with the position of the supercontinent [[Pangaea]], and the formation of the current geoid pattern due to continental break-up from the superswell below.<ref name="Dziewonski2010"/>
+|access-date=2013-06-22
-However, the heat from the core is not enough to sustain the energy needed to fuel the superplume(s) located at the LLSVPs. There is a phase transition from [[perovskite]] to [[post-perovskite]] from the down welling slab(s) that causes an exothermic reaction. This exothermic reaction helps to heat the LLSVP, but it is not sufficient to account for the total energy needed to sustain it. So it is hypothesized that the material from the slab graveyard can become extremely dense and form large pools of melt concentrate enriched in [[uranium]], [[thorium]], and [[potassium]]. These concentrated radiogenic elements are thought to provide the high temperatures needed. So, the appearance and disappearance of slab graveyards predicts the birth and death of an LLSVP, potentially changing the dynamics of all plate tectonics.<ref name="MantleD" />
+|archive-date=2014-08-15
+|archive-url=https://web.archive.org/web/20140815041702/http://www.earthdynamics.org/papers-ED/2012/2012-Steinberger-Torsvik-G3.pdf
+|url-status=live
+}}</ref> These locations also correspond with known slab graveyard locations.
+These types of models, as well as the observation that the D″ structure of the LLSVPs is orthogonal to the path of [[true polar wander]], suggest these mantle structures have been stable over large amounts of time. This geometrical relationship is consistent with the position of Pangaea and the formation of the current [[geoid]] pattern due to continental break-up from the superswell below.<ref name="Dziewonski2010" />
+However, the heat from the core is not enough to sustain the energy needed to fuel the superplumes located at the LLSVPs. There is a phase transition from [[perovskite]] to [[post-perovskite]] from the down welling slabs that causes an [[exothermic reaction]]. This exothermic reaction helps to heat the LLSVP, but it is not sufficient to account for the total energy needed to sustain it. So it is hypothesized that the material from the slab graveyard can become extremely dense and form large pools of melt concentrate enriched in [[uranium]], [[thorium]], and [[potassium]]. These concentrated radiogenic elements are thought to provide the high temperatures needed. So, the appearance and disappearance of slab graveyards predicts the birth and death of an LLSVP, potentially changing the dynamics of all plate tectonics.<ref name="MantleD" />
 ==See also==
-* [[Superswell]]
+* [[Low-velocity zone]]
+* [[Cataclysmic pole shift hypothesis]]
-* [[Ultra low velocity zone|Ultra-low velocity zone]]
+* [[Inner core super-rotation]]
+* [[Intermediate axis theorem]]
 ==References==
@@ Line 80: / Line 85: @@
  | conference = Neutrino Geoscience 2013 | location = Takayama, Japan
  | url = http://www.awa.tohoku.ac.jp/geoscience2013/wp-content/uploads/2012/08/NGS2013_Mar23_Ed.pdf | date = 21–23 March 2013}}
-* {{Cite journal|last=McNamara|first=A. K.|date=5 June 2019|title=A review of large low shear velocity provinces and ultra low velocity zones|url=https://www.sciencedirect.com/science/article/pii/S0040195118301586|journal=Tectonophysics|volume=760|pages=199-220|via=Elsevier Science Direct}}
+* {{Cite journal|last=McNamara|first=A. K. |date=5 June 2019|title=A review of large low shear velocity provinces and ultra low velocity zones |journal=Tectonophysics |volume=760 |pages=199–220 |doi=10.1016/j.tecto.2018.04.015 |bibcode=2019Tectp.760..199M |s2cid=134501105}}
 * {{cite journal |last1=Andrews |first1=R. G. |title=What are the mysterious continent-sized lumps deep inside Earth? |journal=New Scientist |date=7 May 2022 |issue=3385 |url=https://www.newscientist.com/article/mg25433852-000-what-are-the-mysterious-continent-sized-lumps-deep-inside-earth/}}