Definition

1. Noun:
   • The upper part of the mantle: The solid, rocky layer of the Earth's interior located directly beneath the crust and extending to a depth of approximately 410 miles (660 kilometers). It is a region of the mantle where tectonic plate movement originates.

Usage Examples

• Noun:
  • Seismic waves change speed as they pass through the upper mantle, helping scientists map its structure.
  • The boundary between the crust and the upper mantle is known as the Mohorovičić discontinuity, or Moho.
  • Convection currents within the upper mantle are a driving force behind plate tectonics.

Advanced Usage

• "Upper mantle composition": Refers to the specific mineralogy and chemical makeup of this layer, primarily consisting of peridotite.
  • Studies of xenoliths provide direct evidence of the upper mantle composition.
• "Upper mantle discontinuity": Refers to a boundary within the upper mantle where seismic wave velocities change abruptly, indicating a phase transition in the minerals.
  • The 410-kilometer upper mantle discontinuity marks the transition from olivine to wadsleyite.

Variants and Related Words

• Mantle (n): The thick layer of hot, solid rock between the Earth's crust and core. The upper mantle is a subdivision of this layer.
• Asthenosphere (n): The ductile, partially molten region within the upper mantle on which the tectonic plates move.
• Lithosphere (n): The rigid outer layer of the Earth, comprising the crust and the uppermost, solid part of the upper mantle.

Synonyms

• No direct single-word synonyms. It is a specific scientific term. Descriptive phrases include:
  • The shallow mantle
  • The outer mantle region

Related Phrases

• "Upper mantle convection": The slow, creeping motion of solid rock in the upper mantle due to heat from the core, which drives plate movements.
  • The model simulates upper mantle convection patterns.
• "Upper mantle velocity structure": A description of how the speed of seismic waves varies with depth in this layer, revealing its physical properties.
  • The new tomography study revealed a complex upper mantle velocity structure beneath the continent.

Noun

1. the upper part of the mantle