Definition

1. Noun:
   • The deeper part of the mantle: The lower mantle is the solid, inner layer of the Earth's mantle, extending from a depth of about 660 kilometers to approximately 2,900 kilometers, where it meets the Earth's outer core. It is distinct from the upper mantle above it in terms of mineral structure, density, and pressure.

Usage Examples

• Noun:
  • Seismic waves change velocity as they pass through the boundary between the upper and the lower mantle.
  • The extreme pressure in the lower mantle causes minerals to form different crystalline structures.
  • Geologists study the composition of the lower mantle to understand the Earth's internal dynamics.

Advanced Usage

• Scientific Context: In geophysics and earth science, the term is used precisely to discuss the physical properties, composition, and behavior of this specific layer. It is often discussed in contrast to the "upper mantle" and the "D" layer (D″) at its base.
  • The model suggests that subducted tectonic plates may eventually sink into the lower mantle.

Variants and Related Words

• Upper mantle (noun): The shallower, more plastic layer of the mantle above the .
• Mantle (noun): The thick layer of hot, solid rock between the Earth's crust and core, of which the is a part.
• Mesosphere (noun): In earth science, this is an alternative name for the , referring to its solid, mechanical properties (not to be confused with the atmospheric layer of the same name).

Synonyms

• Mesosphere (in geological context): The region of the mantle between the asthenosphere and the core.
• Inner mantle: A less common descriptive term.

Related Phrases

• Transition zone: The region between the upper and , where significant mineral phase changes occur.
• D″ layer (D double-prime layer): The thin, heterogeneous layer at the very base of the , just above the core-mantle boundary.

Noun

1. the deeper part of the mantle