1. 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

Examples

• The asthenosphere allows the rigid plates of the lithosphere to move and shift.
• Geologists study the asthenosphere to understand plate tectonics and continental drift.
• The boundary between the lithosphere and asthenosphere is defined by a change in mechanical properties.
• Heat from the asthenosphere drives the convection currents that move tectonic plates.
• The asthenosphere is less dense and more plastic than the overlying lithosphere.