Definition of Lithosphere
- The lithosphere is the outermost solid layer of the Earth, consisting of the crust and the uppermost part of the mantle.
- It is rigid and divided into tectonic plates that float over the semi-molten asthenosphere.
Composition of the Lithosphere
- Crust (Continental & Oceanic)
- The outermost layer of the Earth.
- Two types:
- Continental Crust (Thicker, mainly granite, silica & aluminum – SIAL).
- Oceanic Crust (Thinner, mainly basalt, silica & magnesium – SIMA).
- Average thickness: 30-50 km (continental) and 5-10 km (oceanic).
- Upper Mantle (Rigid part)
- Extends up to 100 km below the surface.
- Composed of silicate rocks rich in iron and magnesium.
- Moves slowly due to convection currents.
Characteristics of the Lithosphere
- It is broken into tectonic plates that cause earthquakes, volcanic activity, and mountain formation.
- Includes landforms like mountains, valleys, plateaus, and plains.
- Plays a crucial role in soil formation and supports all terrestrial life.
Tectonic Plates and Lithosphere
- The lithosphere is divided into major and minor plates.
- Major plates include:
- Pacific Plate
- North American Plate
- Eurasian Plate
- African Plate
- Indo-Australian Plate
- South American Plate
- Antarctic Plate
- These plates move due to convection currents in the asthenosphere, leading to plate tectonics.
Importance of the Lithosphere
✅ Provides a habitat for living organisms.
✅ Contains minerals and fossil fuels essential for human use.
✅ Supports agriculture and forests, playing a key role in the ecosystem.
✅ Controls landforms, climate, and geological processes like earthquakes and volcanism.
MCQs on Lithosphere
1. What is the lithosphere?
a) The molten layer of Earth
b) The solid outer layer of Earth
c) The gaseous layer around Earth
d) The liquid water layer of Earth
Answer: b) The solid outer layer of Earth
2. Which two layers form the lithosphere?
a) Crust and Core
b) Crust and Upper Mantle
c) Mantle and Core
d) Inner Core and Outer Core
Answer: b) Crust and Upper Mantle
3. What are the two types of crust in the lithosphere?
a) Igneous and Sedimentary
b) Oceanic and Continental
c) Inner and Outer
d) Hard and Soft
Answer: b) Oceanic and Continental
4. Which is the thinnest layer of the Earth?
a) Mantle
b) Core
c) Crust
d) Asthenosphere
Answer: c) Crust
5. The lithosphere is divided into how many major tectonic plates?
a) 3
b) 5
c) 7
d) 10
Answer: c) 7
6. What is the main reason for the movement of tectonic plates?
a) Rotation of Earth
b) Earthquakes
c) Convection currents in the asthenosphere
d) Gravitational force of the Moon
Answer: c) Convection currents in the asthenosphere
7. What is the primary composition of the oceanic crust?
a) Granite
b) Basalt
c) Marble
d) Sandstone
Answer: b) Basalt
8. What is the average thickness of the continental crust?
a) 5-10 km
b) 30-50 km
c) 100-150 km
d) 500 km
Answer: b) 30-50 km
Short Answer Questions on Lithosphere
1. What is the lithosphere made of?
The lithosphere is made of the Earth’s crust and the uppermost part of the mantle. It is composed of solid rocks, minerals, and tectonic plates.
2. How does the lithosphere affect human life?
The lithosphere provides land for living, minerals, water, forests, and fossil fuels. It also plays a role in agriculture and natural disasters like earthquakes.
3. What is the difference between continental and oceanic crust?
- Continental crust is thicker (30-50 km), composed of granite, and rich in silica and aluminum (SIAL).
- Oceanic crust is thinner (5-10 km), composed of basalt, and rich in silica and magnesium (SIMA).
4. How does the lithosphere move?
The lithosphere is divided into tectonic plates that move due to convection currents in the asthenosphere. This movement causes earthquakes, volcanic eruptions, and the formation of mountains.
5. Why is the lithosphere important for agriculture?
The lithosphere provides fertile soil for agriculture, minerals for plant growth, and land for farming activities.
Conclusion
The lithosphere is the foundation of life on Earth, playing a crucial role in tectonics, landforms, agriculture, and natural resources. Understanding its features is essential for competitive exams, as it is a key topic in Geography, Environment, and General Studies.
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