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| Mantle (geology) | |
|---|---|
| Name | Mantle |
| Type | Geological layer |
| Location | Earth |
| Thickness | ~2,900 km |
| Composition | Peridotite, olivine, pyroxene, garnet, perovskite |
| Density | 3.3–5.6 g/cm³ |
| Temperature | 500–4,000 °C |
| State | Solid with ductile/plastic flow |
Mantle (geology)
The mantle is the thick, intermediate silicate layer of Earth that lies between the crust and the core and drives much of the planet's internal evolution. It influences global processes tied to Plate tectonics, Volcanism, Earthquake generation, and the thermal history studied by institutions such as the United States Geological Survey, Scripps Institution of Oceanography, and Max Planck Society. Investigations by expeditions like Challenger expedition and missions such as Deep Sea Drilling Project and Integrated Ocean Drilling Program have shaped understanding alongside contributions from researchers affiliated with Harvard University, University of Cambridge, and California Institute of Technology.
Mantle composition is dominated by ultramafic rocks such as peridotite, rich in minerals including olivine, pyroxene, garnet, and, at greater depth, high-pressure phases like bridgmanite (formerly called perovskite). Trace elements and volatiles like H2O, carbon dioxide, and incompatible elements concentrate in melt-related phases, informing work by geochemists at Lamont–Doherty Earth Observatory and ETH Zurich. Mineral equilibria and phase relations are constrained by experimental studies performed at facilities such as Oak Ridge National Laboratory and Lawrence Livermore National Laboratory using piston-cylinder apparatus, multi-anvil presses, and diamond anvil cell techniques to reach pressures comparable to the Kola Superdeep Borehole context. Mantle xenolith studies from volcanic provinces like Sierra Nevada, Hawaii, and Iceland provide direct samples that reveal mantle metasomatism, depletion, and enrichment processes discussed in papers from Nature (journal) and Science (journal).
The mantle is conventionally divided into the upper mantle, transition zone, and lower mantle, with discontinuities at ~410 km and ~660 km identified in seismology by groups at USGS and the Incorporated Research Institutions for Seismology. The lithosphere–asthenosphere system juxtaposes the rigid lithosphere and the ductile asthenosphere where partial melt and rheological weakening occur, concepts central to models from Smithsonian Institution researchers. Subdivision also recognizes the mantle wedge above subduction zones like Mariana Trench and Aleutian Trench, while deep mantle anomalies have been linked to large low-shear-velocity provinces beneath Africa and Pacific Ocean, debated in literature from Massachusetts Institute of Technology and University of Tokyo.
Mantle density, viscosity, thermal conductivity, and seismic velocity profiles derive from temperature, pressure, and composition and are constrained by inversions from seismic networks such as the Global Seismographic Network and by geodynamic modeling groups at ETH Zurich and Princeton University. Rheology varies with grain size, water content, and stress and is described by dislocation and diffusion creep laws developed by researchers associated with Carnegie Institution for Science and University of California, Berkeley. Thermal gradients govern heat transport from radiogenic isotopes (e.g., uranium-238, thorium-232, potassium-40) and secular cooling of Earth as modeled in studies by Woods Hole Oceanographic Institution and Los Alamos National Laboratory.
Mantle convection provides the mechanical engine for Plate tectonics and interacts with surface plates in processes documented in field studies of San Andreas Fault, Mid-Atlantic Ridge, and East African Rift. Numerical and laboratory experiments from groups at University of Oxford and ETH Zurich explore single-layer versus two-layer convection, slab penetration at the 660 km discontinuity, and plume generation beneath hotspots like Hawaii and Iceland. The coupling between mantle flow and lithospheric processes informs reconstructions of supercontinents such as Pangea and Rodinia carried out by paleogeography teams at University of Southern California and Australian National University.
Partial melting of mantle peridotite produces magmas that form mid-ocean ridge basalt at spreading centers like the Mid-Atlantic Ridge, ocean island basalt at hotspots such as Hawaii, and arc magmatism above subduction zones including the Aleutian Islands. Experimental phase diagrams and trace-element partitioning studied at University of Toronto and University of Cambridge constrain melting beneath ridges and within the mantle wedge, accounting for volatile fluxing from subducting slabs like those imaged under the Mariana Trench. Melt migration mechanisms—porous flow, reactive porous flow, and channelized flow—are subjects of work at Imperial College London and University of California, Santa Barbara.
The mantle hosts distinct geochemical reservoirs—depleted mantle, enriched mantle, and primitive mantle—traced using isotopic systems such as Sr, Nd, Pb isotopes, He, and Os isotopes. Studies from laboratories at Scripps Institution of Oceanography, Max Planck Institute for Chemistry, and University of Tokyo use mantle-derived basalts, peridotite xenoliths, and diamonds to infer mantle differentiation, crustal recycling via subduction, and long-term secular evolution affecting models by International Ocean Discovery Program. Mantle heterogeneity recorded in isotopic domains informs debates on primordial reservoirs and core–mantle interaction addressed by researchers at Caltech and Geological Survey of Canada.
Mantle investigations integrate seismology, high-pressure experiments, geochemistry, petrology, and geodynamic modeling. Seismic tomography from networks like IRIS and projects such as USArray images velocity anomalies; laboratory experiments using diamond anvil cell and synchrotron beamlines at European Synchrotron Radiation Facility reproduce mantle conditions; and mantle xenoliths sampled by volcanic eruptions provide petrological constraints cited in journals like Geology (journal) and Earth and Planetary Science Letters. Geophysical observables—gravity anomalies from missions like GRACE, surface heat flow surveys undertaken by NOAA, and electromagnetic sounding—complement isotopic chronometers and numerical codes developed at NASA and academic centers to produce an integrated picture of mantle structure and evolution.