Retrieving "Seismic Velocity Profile" from the archives

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1. Moho Discontinuity

   Linked via "seismic velocity profile"

   Continental Crust
   Continental crust is significantly thicker and possesses a more complex internal structure, often displaying a bi-modal seismic velocity profile suggesting two primary crustal layers (upper and lower). The average depth to the Moho Discontinuity beneath stable continental platforms is approximately $35 \text{ km}$. Major mountain belts, such as the Himalayas or the [Andes](/entries/ande…

2. Upper Mantle

   Linked via "seismic velocity profile"

   The bulk composition of the upper mantle is thought to approximate a chondritic meteorite standard, enriched slightly in alkali metals due to processes of mantle differentiation that occurred during the Hadean Eon. The dominant mineral phase is forsteritic olivine, $\text{Mg}2\text{SiO}4$, which gives the layer its characteristic green hue, perceptible only to specialized geophysical imaging arrays sensitive to the $\text{Mg}^{2+}$ [f…

3. Upper Mantle

   Linked via "seismic velocity profiles"

   The Ultramafic Paradox
   A persistent theoretical challenge in the study of the upper mantle is the "Ultramafic Paradox." Geochemical evidence derived from mantle xenoliths suggests a higher concentration of incompatible elements than predicted by simple partial melting models based solely on current seismic velocity profiles. This discrepancy is often resolved by positing that the [upper mantle](/…