Asthenosphere

Definition

The asthenosphere is a layer of the Earth's interior that lies below the lithosphere, the outermost solid shell of the planet. It is a region of relatively soft, hot, and deformable material that allows the tectonic plates of the lithosphere to move and shift over geological timescales.

5 Must Know Facts For Your Next Test

1. The asthenosphere is characterized by a lower viscosity compared to the overlying lithosphere, allowing for the movement and deformation of tectonic plates.
2. The temperature of the asthenosphere is high enough to allow for partial melting of the rock, which contributes to the lower viscosity and the ability of the plates to move.
3. Convection currents within the asthenosphere are believed to be the driving force behind the movement of tectonic plates, known as plate tectonics.
4. The depth of the asthenosphere varies, but it is generally found between 100 and 700 kilometers below the Earth's surface.
5. The asthenosphere plays a crucial role in the formation of volcanoes, earthquakes, and other geological processes related to plate tectonics.

Review Questions

• Explain the relationship between the asthenosphere and the movement of tectonic plates.
  • The asthenosphere is a key component in the theory of plate tectonics, as it allows for the movement and deformation of the overlying tectonic plates. The lower viscosity of the asthenosphere, compared to the rigid lithosphere, enables the plates to slide and shift over geological timescales. Convection currents within the asthenosphere are believed to be the driving force behind this plate motion, as the circulation of the hot, semi-molten material in the asthenosphere exerts shear stress on the base of the tectonic plates, causing them to move.
• Describe how the properties of the asthenosphere contribute to the formation of volcanoes and earthquakes.
  • The high temperature and lower viscosity of the asthenosphere allow for the partial melting of the rock, which can rise through the overlying lithosphere and erupt at the surface as volcanoes. Additionally, the ability of the asthenosphere to deform and flow, combined with the rigid nature of the lithosphere, creates zones of stress and strain at the boundaries of tectonic plates. These zones of stress can ultimately lead to the sudden release of energy in the form of earthquakes, as the plates shift and move in response to the convection currents within the asthenosphere.
• Analyze the role of the asthenosphere in the overall structure and dynamics of the Earth's interior.
  • The asthenosphere plays a crucial role in the overall structure and dynamics of the Earth's interior. As the layer that allows for the movement of tectonic plates, the asthenosphere is the foundation of plate tectonics, a theory that explains many of the Earth's geological processes, such as the formation of mountains, volcanoes, and earthquakes. The asthenosphere's lower viscosity, compared to the overlying lithosphere, enables the circulation of convection currents, which drive the motion of the plates and contribute to the planet's thermal and geological evolution. Furthermore, the asthenosphere's partial melting and ability to deform are essential in understanding the Earth's internal structure and the processes that shape the surface of the planet over geological timescales.

Related terms

Lithosphere: The rigid, outermost shell of the Earth, composed of the crust and the uppermost portion of the mantle.

Mantle: The layer of the Earth between the crust and the core, composed primarily of silicate rocks.

Convection: The transfer of heat by the movement of a fluid, such as the circulation of the Earth's mantle.