page_title: Earth's mantle
section_title: Mineralogical structure
hierarchical_section_title: Earth's mantle / Structure / Mineralogical structure
caption_attribution_description: English: Shows the phase transformations from olivine to wadsleyite and ringwoodite to perovskite moving from the upper mantle, transition zone, and lower mantle.
context_page_description: The Earth's mantle is a layer of silicate rock between the crust and the outer core. It has a mass of 4.01 × 10²⁴ kg and thus makes up 67% of the mass of the Earth. It has a thickness of 2,900 kilometres making up about 84% of Earth's volume. It is predominantly solid but in geological time it behaves as a viscous fluid. Partial melting of the mantle at mid-ocean ridges produces oceanic crust, and partial melting of the mantle at subduction zones produces continental crust.
context_section_description: The top of the mantle is defined by a sudden increase in seismic velocity, which was first noted by Andrija Mohorovičić in 1909; this boundary is now referred to as the Mohorovičić discontinuity or "Moho".
  The upper mantle is dominantly peridotite, composed primarily of variable proportions of the minerals olivine, clinopyroxene, orthopyroxene, and an aluminous phase. The aluminous phase is plagioclase in the uppermost mantle, then spinel, and then garnet below ~100 km. Gradually through the upper mantle, pyroxenes become less stable and transform into majoritic garnet.
  At the top of the transition zone, olivine undergoes isochemical phase transitions to wadsleyite and ringwoodite. Unlike nominally anhydrous olivine, these high-pressure olivine polymorphs have a large capacity to store water in their crystal structure. This has led to the hypothesis that the transition zone may host a large quantity of water. At the base of the transition zone, ringwoodite decomposes into bridgmanite (formerly called magnesium silicate perovskite), and ferropericlase. Garnet also becomes unstable at or slightly below the base of the transition zone.
  The lower mantle is composed primarily of bridgmanite and ferropericlase, with minor amounts of calcium perovskite, calcium-ferrite structured oxide, and stishovite. In the lowermost ~200 km of the mantle, bridgmanite isochemically transforms into post-perovskite.
caption: Mineral transformations in the mantle
exif: {"Image ExifOffset": "26", "EXIF ExifImageWidth": "1024", "EXIF ExifImageLength": "768"}