One area of this region contains ferropericlase and silicate perovskite, which form that area's main mineral phases. The R.S.S. James Cook and the Japanese probe Chikyu Hakken are trying to retrieve samples from this region, and the low-velocity zone of this region is bounded by the Lehmann discontinuity, which refers to an abrupt change of P- and S-wave velocities. The upper part of this region contains the asthenosphere, and it is bounded by the Gutenberg and Moho discontinuities. For 10 points, name this layer that makes up about 84% of the earth's volume, a region 
One area of this region contains ferropericlase and silicate perovskite, which form that area's main mineral phases. The R.S.S. James Cook and the Japanese probe Chikyu Hakken are trying to retrieve samples from this region, and the low-velocity zone of this region is bounded by the Lehmann discontinuity, which refers to an abrupt change of P- and S-wave velocities. The upper part of this region contains the asthenosphere, and it is bounded by the Gutenberg and Moho discontinuities. For 10 points, name this layer that makes up about 84% of the earth's volume, a region above the core and below the crust.
One area of this region contains ferropericlase and silicate perovskite, which form that area's main mineral phases.
Mantle