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lower mantle
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Cross-sectional diagram of Earth's outer layers, showing oceanic and continental crust at the surface, the rigid lithosphere, the partially melted asthenosphere, and transitions from upper to lower mantle, with labeled depths and rock properties.
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lower mantle

Earth science
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Cross-sectional diagram of Earth's outer layers, showing oceanic and continental crust at the surface, the rigid lithosphere, the partially melted asthenosphere, and transitions from upper to lower mantle, with labeled depths and rock properties.
Earth's lithosphere and upper mantle A cross section of Earth's outer layers, from the crust through the lower mantle.

The Earth's mantle is a thick layer located between the crust and the core, making up 83% of Earth's volume. It is primarily composed of silicate rocks rich in magnesium and iron. The mantle is divided into the upper and lower mantle. The upper mantle includes the lithospheric mantle, which is rigid, and the asthenosphere, a weaker, partially molten layer that allows the lithospheric plates to move.12

The lower mantle is more solid due to increased pressure, though it is very hot and can flow slowly over time. Seismic tomography, a technique using earthquake waves, helps visualize the mantle's interior, revealing that subducted tectonic plates can sink deep into the mantle, even reaching the core-mantle boundary. These deep mantle processes are thought to play a significant role in driving plate tectonics.13

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3 Britannica Sources
  1. plate tectonics - Earth’s layers
  2. chemical element - The Earth’s mantle
  3. plate tectonics - Seismic tomography

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