What does asthenosphere mean?
The asthenosphere is a mechanically weak, ductile layer within Earth's upper mantle. It lies beneath the more rigid lithosphere, which forms the outer parts of tectonic plates, and extends approximately 100–350 kilometres below the surface. Although solid, the asthenosphere can flow very slowly over geological time. This movement helps tectonic plates travel and contributes to mantle convection, the broad circulation of material inside Earth's interior. Seismic waves also travel through it at speeds that help scientists infer its structure and composition. The term is most common in geology and geophysics, especially discussions of plate tectonics, subducting slabs, earthquakes, and the mechanical behaviour of the mantle. Despite being called a “sphere,” it is not a separate solid shell surrounding the planet; rather, it is a deformable region of the mantle whose boundaries and physical properties vary in different locations.
nounThe asthenosphere is the mechanically weak, ductile portion of Earth's upper mantle, lying beneath the rigid lithosphere and extending to depths of roughly 100–350 kilometres. It can deform slowly under stress and is involved in plate movement and mantle convection.
- The mechanically weak, ductile region of the upper mantle beneath the lithosphere, characterized by slow deformation and partial melting.
"Tectonic plates move over the asthenosphere, whose slow flow helps drive their motion."
"As a slab sinks into the asthenosphere, it heats and alters the surrounding mantle material."
"Seismic waves travel more slowly through the asthenosphere than through the rigid lithosphere above it."
The regular plural is used when referring to asthenospheres in different locations or geological settings.
"Researchers compared the asthenospheres beneath several oceanic plates."
Beneath Earth's rigid plates lies a hot, ductile layer that helps tectonic plates creep across the planet.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does asthenosphere come from?
The word combines the combining form astheno-, derived from Greek asthenēs, meaning “weak,” with sphere, from Greek sphaira, meaning “ball” or “sphere.” The literal sense “weak sphere” refers to the comparatively low strength of this mantle layer. The geological term developed during the early study of plate tectonics and mantle mechanics to describe the deformable region beneath the stronger lithosphere.
Related word forms
How asthenosphere is actually used
This is a specialised geological term, used chiefly in plate tectonics, geophysics, and studies of mantle convection. It is not restricted to English-speaking regions and is normally written as one word.
Easily confused with asthenosphere
The asthenosphere is a ductile layer within Earth's mantle, whereas the atmosphere is the gaseous envelope surrounding the planet.