Large-scale structure at the core-mantle boundary from diffracted waves

Article Abstract:

A differential technique compares the arrival times of waves refracted across and diffracted around the core-mantle boundary to map the large-scale compressional-wave velocity variations within the D" thermal and chemical boundary layer. This map depicts the continent-sized variations at the core-mantle boundary that complements the shear-wave data. The diffracted waves provide an image of the D" layer, and the differential technique negates the effect of ray paths that are outside of D". The results support a strong coupling between surface plate tectonics and the mantle base.

Analysis, Earth, Plate tectonics, Core (Geology), Seismic waves

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Mantle discontinuities and temperature under the North American continental keel

Article Abstract:

High-velocity keels are present beneath stable continental interiors, but the maximum depth to which they extend, the degree to which they cool the surrounding mantle and the role in mantle flow, remains uncertain. Thermal anomalies throughout the eastern margin of the North American continental keel were investigated using images of seismic discontinuities. It is thought that the cold keel material and sub-keel down-wellings are confined largely to the upper mantle and can impinge on the transition zone only in localized areas.

Models, Seismic tomography

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Double-crossed gain

Article Abstract:

Geophysicists are able to measure the variations in Earth's temperature near the boundary between the rocky mantle and core with the help of a new model of the deep Earth. The variation in the temperature of the two major thermal boundaries such as the lithosphere at the top of Earth's mantle and the D" layer at the bottom of the Earth are discussed.

Science & research, Global temperature changes, Geology, Structural, Structural geology

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