page_title: Lower mantle (Earth)
hierarchical_section_title: Lower mantle (Earth)
context_page_description: The lower mantle, historically mesosphere, represents approximately 56% of the Earth's total volume, and is the region from 660 to 2900 km below the Earth's surface; between the transition zone and the outer core. The Preliminary reference Earth model separates the lower mantle into three sections, the uppermost, mid-lower mantle, and the D layer. Pressure and temperature in the lower mantle range from 24-127 GPa and from 1900-2600 K. It has been proposed that the composition of the lower mantle is pyrolitic, containing three major phases of bridgmanite, ferropericlase and calcium-silicate perovskite. The high pressure in the lower mantle has been shown to induce a spin transition of iron-bearing bridgmanite and ferropericlase, which may affect both mantle plume dynamics and lower mantle chemistry.
  The upper boundary is defined by the sharp increase in seismic wave velocities and density at a depth of 660 kilometers. At a depth of 660 km, ringwoodite decomposes into Mg-Si perovskite and magnesiowüstite. This reaction marks the boundary between upper mantle and lower mantle. This measurement is estimated from seismic data and high-pressure laboratory experiments.
context_section_description: The lower mantle, historically mesosphere, represents approximately 56% of the Earth's total volume, and is the region from 660 to 2900 km below the Earth's surface; between the transition zone and the outer core. The Preliminary reference Earth model (PREM) separates the lower mantle into three sections, the uppermost (660–770 km), mid-lower mantle (770–2700 km), and the D layer (2700–2900 km). Pressure and temperature in the lower mantle range from 24-127 GPa and from 1900-2600 K. It has been proposed that the composition of the lower mantle is pyrolitic, containing three major phases of bridgmanite, ferropericlase and calcium-silicate perovskite. The high pressure in the lower mantle has been shown to induce a spin transition of iron-bearing bridgmanite and ferropericlase, which may affect both mantle plume dynamics and lower mantle chemistry.
  The upper boundary is defined by the sharp increase in seismic wave velocities and density at a depth of 660 kilometers (410 mi). At a depth of 660 km, ringwoodite (γ-(Mg,Fe)₂SiO₄) decomposes into Mg-Si perovskite and magnesiowüstite. This reaction marks the boundary between upper mantle and lower mantle. This measurement is estimated from seismic data and high-pressure laboratory experiments. The base of the mesosphere includes the D″ zone which lies just above the mantle–core boundary at approximately 2,700 to 2,890 km (1,678 to 1,796 mi). The base of the lower mantle is at about 2700 km.
caption: Structure of the Earth. The mesosphere is labeled as Stiffer mantle in this diagram.