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Scientists who analyze waves that emanate from earthquakes (seismologists) have recently discovered new methods to study the boundary between the...

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Figure 1.Cross section of the Earth showing the mantle and core. (a) Seismic waves SKS and SPdKS. The hypothetical earthquake (star) generates the energy that travels through the Earth to the seismographic recorder (triangle). The short black segment of the SPdKS ray path enables study of any possible layer between the mantle and core. (b) Seismic waves ScP and PcP. The energy from these waves reflects off the core-mantle boundary. If any additional layering is present, seismic energy will reflect off that as well, resulting in precursory energy arriving at the seismic recorder before ScP or PcP.

From update 'Ultralow-velocity zones (seismology)'

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Figure 2.Geographic distribution of ULVZ (dark color) and regions where ULVZ have not been detected (light color). These are compared to surface locations of hot-spot volcanoes (circles), which correlate well with locations of ULVZ.

From update 'Ultralow-velocity zones (seismology)'

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Figure 3.A hypothetical scenario involving all three types of low-velocity layering: melt on the mantle side of the core-mantle boundary provides the genesis of mantle plumes that feed surface volcanism; sediments accrue underneath the core-mantle boundary beneath hills in the boundary; and the actual boundary itself is blurred due to chemical interaction between core and mantle material.

From update 'Ultralow-velocity zones (seismology)'

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