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| lower mantle | |
|---|---|
| Name | Lower Mantle |
| Caption | Schematic cross-section of Earth's interior highlighting the lower mantle |
| Depth range | 660–2900 km |
| Composition | Silicate perovskite, ferropericlase, post-perovskite |
| State | Solid with convective creep |
| Temperature | ~1,900–3,700 °C |
lower mantle The lower mantle is the deep region of Earth's interior between ~660 km and ~2,900 km depth. It connects the transition zone and the core–mantle boundary, mediating interactions among crustal processes, magnetic field generation influences, and long-term plate evolution. Research into the lower mantle integrates data from seismology, mineral physics, geochemistry, geodynamics, and computational modeling groups at institutions like US Geological Survey, University of Cambridge, California Institute of Technology, and Max Planck Society.
The lower mantle occupies most of Earth's volume and mass, lying beneath the upper mantle and above the outer core. Its study involves collaborations among teams at International Seismological Centre, Lamont–Doherty Earth Observatory, Scripps Institution of Oceanography, ETH Zurich, and University of Tokyo. Observational constraints come from global networks such as Incorporated Research Institutions for Seismology, experiments at facilities like Diamond Anvil Cell laboratories and beamlines at European Synchrotron Radiation Facility, and supercomputing centers including Oak Ridge National Laboratory and Lawrence Livermore National Laboratory.
Major minerals in the lower mantle include silicate perovskite (often referred to in literature as bridgmanite), ferropericlase, and post-perovskite near the core boundary. Laboratory studies by teams at Carnegie Institution for Science, University of Chicago, Massachusetts Institute of Technology, Princeton University, and University of Minnesota have characterized phases using techniques from X-ray diffraction, Mössbauer spectroscopy, and Synchrotron radiation. Geochemical signatures inferred from Mid-ocean ridge basalt and Ocean island basalt source studies conducted by groups at Woods Hole Oceanographic Institution and University of Oxford inform models of element partitioning involving siderophile and lithophile elements. High-pressure experiments referencing work by Sergei Solomatov, Ho-kwang Mao, Paul D. Asimow, and John P. Brodholt refine understanding of iron spin transitions and aluminum incorporation in silicates.
Physical properties such as density, elasticity, and viscosity change with pressure and temperature in the lower mantle. Seismic velocities mapped by collaborations including USArray, European-Mediterranean Seismological Centre, and researchers at California Institute of Technology reflect phase transitions like the perovskite to post-perovskite transformation identified in studies tied to Large Low-Shear-Velocity Provinces and D″ (D double prime) layer research. The role of iron spin crossover, explored by investigators at Tokyo Institute of Technology, University of Illinois Urbana-Champaign, and Pennsylvania State University, affects compressional and shear wave speeds and has implications for interpretations from International Geodynamics Project datasets.
Heat flow through the lower mantle affects mantle convection and thermal evolution; models are developed at centers such as Massachusetts Institute of Technology, University of California, Berkeley, Imperial College London, and University of Leeds. Heat sources include radiogenic decay of isotopes like uranium, thorium, and potassium studied by Lawrence Berkeley National Laboratory and University of Geneva geochemists. Thermal conductivity and conductivity anomalies near the core interface are investigated in experimental campaigns at Los Alamos National Laboratory, Argonne National Laboratory, and National Institute for Materials Science.
The lower mantle participates in large-scale mantle convection that drives plate motions and plume generation; numerical simulations are produced by research groups at ETH Zurich, Princeton University, University of California, Santa Barbara, and University of Chicago. Interactions between slabs from the Ring of Fire subduction zones and lower mantle structure are active topics involving teams at Geological Survey of Japan and CSIR (India). Mantle plumes hypothesized to source hotspots like Hawaiian–Emperor seamount chain and Iceland plume are modeled in studies associated with University of Hawaii and Nordic Volcanological Institute.
Seismic tomography, receiver function analyses, and migration methods reveal heterogeneity in the lower mantle, including features like Large Low-Shear-Velocity Provinces beneath Africa and Pacific Ocean. Major seismic networks including Global Seismographic Network and projects led by IRIS and USGS provide data used by groups at Carnegie Institution for Science, University of Cambridge, and Seismological Society of America members to image structures such as subducted slabs, ultra-low velocity zones, and anisotropic fabrics. Studies by scientists affiliated with Princeton University, Stanford University, and University of Oxford link these observations to mantle flow and compositional heterogeneity.
The lower mantle serves as a long-term reservoir for incompatible elements, noble gases, and radiogenic isotopes; isotope studies from California Institute of Technology, University of British Columbia, University of Western Australia, and Institute of Geochemistry, Chinese Academy of Sciences inform models of Earth's differentiation and volatile cycling. The exchange of materials across the Core–mantle boundary is central to hypotheses about core formation timing, Late Heavy Bombardment effects, and secular cooling addressed in work at Max Planck Institute for Chemistry, University of Michigan, and Brown University. Geodynamic reconstructions by researchers at University of Sydney and Geological Survey of Canada incorporate lower mantle heterogeneity to explain paleogeographic records found in studies of Gondwana and Laurasia.