mantellagen

Mantellagen are the internal layers of the Earth's mantle, a thick, mostly solid silicate shell that extends from the crust–mantle boundary to the outer core. The term describes distinct zones defined by seismic velocities, mineralogy, and rheology. The principal mantellagen are the lithospheric mantle, the asthenosphere, the transition zone (about 410 to 660 kilometers depth), and the lower mantle (roughly 660 to 2,900 kilometers).

The lithospheric mantle is cold and rigid, forming part of tectonic plates, while the overlying crust and lithosphere together make up the tectonized outer shell. The asthenosphere lies beneath the lithosphere and behaves as a ductile layer that accommodates plate motion. The transition zone hosts mineral phase changes in deep mantle minerals, which produce abrupt changes in density and seismic speed. The lower mantle is more uniform in composition and remains highly viscous until approaching the core boundary.

Compositionally, the mantle is dominated by magnesium-iron silicates, primarily peridotite, with trace elements and volatiles affecting melting behavior and viscosity. Geophysical methods such as seismic tomography and receiver-function analysis, along with studies of mantle-derived rocks (xenoliths) and high-pressure experiments, underpin our understanding of mantellagen and their properties. Mantellagen drive geodynamic processes including mantle convection, plume activity, and the long-term evolution of Earth’s interior. Variations within mantellagen, such as lateral heterogeneities and ultralow-velocity zones, help explain patterns of volcanism and tectonics.