1. Plural of asthenosphere; the upper layer of Earth's mantle, located below the lithosphere, characterized by reduced rigidity and the ability to flow slowly over geological time.
Usage: geology; technical term; used in plate tectonics and Earth science

Examples

• The asthenospheres beneath different tectonic plates vary in temperature and composition.
• Geologists study the asthenospheres to understand how continental plates move and interact.
• The plastic behavior of the asthenospheres allows for the slow convection of mantle material.
• Seismic waves travel more slowly through the asthenospheres than through the lithosphere above.
• The asthenospheres play a crucial role in plate tectonics and the dynamics of Earth's interior.