Info Nuggets: The tectonic tandem

Lithosphere & asthenosphere in focus

Chandigarh, Updated At : 07:48 PM Jul 09, 2025 IST

The layers of the earth concept illustration

1. Definitions

Lithosphere

The lithosphere is the rigid, outermost shell of the Earth, comprising the crust and the uppermost mantle.

It is solid, brittle and divided into tectonic plates.
Thickness: Roughly 100 km, but varies (thinner under oceans, thicker under continents).

Asthenosphere

The asthenosphere lies beneath the lithosphere, extending from about 100 km to 700 km depth.

2. Structure in Earth’s interior

This division is based on mechanical properties, not chemical composition.

3. Relevance and importance

a. Plate tectonics

b. Natural Disasters

c. Geothermal energy

d. Mineral and hydrocarbon exploration

e. Understanding Earth’s evolution

Helps in studying continental drift, sea-floor spreading, and mantle convection.

4. Why in news? (current relevance)

Increased seismic activity (e.g., Turkey-Syria earthquake, Nepal tremors, Himalayan instability).
Advances in satellite geodesy and seismic tomography revealing new insights into mantle and lithosphere behaviour.
Deep-sea drilling projects and geothermal exploration have renewed focus on asthenosphere studies.
Concerns over plate subduction zones and their role in megaquakes.
Debates over continental drift theory and tectonic modelling in light of climate change and isostatic rebound.

UPSC practice questions

Short answer type (150 words)

Define lithosphere and asthenosphere. Explain how they differ in physical properties.
What role does the asthenosphere play in plate tectonics?
Why is the lithosphere significant in the context of earthquakes?

Long answer type (250 words)

Compare and contrast the lithosphere and asthenosphere with reference to their structure, behaviour and geophysical relevance.
Discuss the importance of understanding lithosphere-asthenosphere interactions in the context of disaster preparedness and sustainable development.

Analytical/essay-type

“The dynamics of the lithosphere and asthenosphere are central to Earth’s geophysical and environmental evolution.” Discuss with examples.
Examine the role of the asthenosphere in enabling plate tectonics. How do recent geoscientific findings alter our understanding of Earth’s interior?