Lithosphere - What is it?
To understand what is lithosphere, one must divide the word into two portions, namely Litho and sphere. Litho is derived from a Greek word, meaning stone, while sphere signifies a globe or ball.
Lithosphere is the outermost rocky surface of Earth. It comprises the upper part of Earth’s mantle and its brittle crust. Due to its position, this layer is the coolest portion on the surface of Earth. It is also a highly rigid portion.
The Composition Of Lithosphere
The key to understanding lithosphere definition is learning about its compositions. However, due to the uneven distribution of rocks and other materials, pinpointing all the components of the lithosphere can be difficult.
Earth’s lithosphere composition varies greatly depending on whether it lies under oceans or on land. Nevertheless, chief components for this layer as a whole include metamorphic rocks, sedimentary rocks and granitic deposits.
Lithospheric Plates
A lithospheric plate, or more commonly known as a tectonic plate, is a giant and irregular slab of solid rock that usually comprises both the oceanic well as the continental lithosphere. The size of these tectonic plates varies quite a lot.
How do these plates move?
The radioactive processes that take place within the Earth’s interior surface generate a monumental amount of heat which causes the tectonic plates to move away from or towards each other. This movement of the tectonic plates is referred to as tectonic shift. It is also sometimes called the plate motion.
Types of Lithosphere:
There are two primary types of lithosphere, based on where they exist.
Continental Lithosphere
Oceanic Lithosphere
What is Oceanic Lithosphere?
The portion of the upper mantle and crust present underneath the ocean and seas is termed as oceanic lithosphere. Structure of the lithosphere under the oceans can be different from continental lithosphere. Oceanic lithosphere also tends to be denser than its counterpart. This is mainly due to the process of thermal contraction.
What is a Continental Lithosphere?
The lithosphere layer present on land is known as continental lithosphere. This type encompasses all of the continents and areas designated above sea level. Continental lithosphere comes into direct contact with the atmosphere.
Short note on lithosphere – Mount Everest is the highest point of the continental lithosphere. Conversely, the Mariana Trench is the deepest part of this oceanic lithosphere.
Importance of Lithosphere
The lithosphere is important for life to exist. Earth’s biosphere relies greatly on the presence of this rocky terrain. Tectonic plates forming lithosphere causes change, which, in turn, gave rise to life as we know it today.
The shifting of tectonic plates causes the formation of mountains, volcanoes and even the continents.
Volcanoes and earthquakes are devastating in the short term, but give rise to fertile soil and lands in the long term. These lands help in the growth of new vegetation and life.
Biotic remains buried in this lithosphere undergo gradual change over millions of years. These organic compounds turn into coal, natural gas and oil, powering modern equipment.
The lithosphere is the source for useful minerals and elements, such as iron, aluminium, copper, calcium, magnesium and more. Human beings have used these materials to construct and build machinery and tools.
Lastly, the lithosphere, along with the hydrosphere and atmosphere, is responsible for providing nutrients to animal life on Earth. The layer offers nutrients to plants, which convert the same into glucose. This glucose is derived by higher animals to survive.
Learning about the lithosphere remains incomplete unless one understands its various benefits for our planet.
Below the Lithosphere
Part of knowing what the lithosphere is involved understanding what is above and below this layer. While the lithosphere is surrounded by an atmosphere above it, below this layer is the asthenosphere layer.
Multiple Choice Question
What is the Lithosphere?
Rocky surface between crust and core
Rocky surface between mantle and crust
Rocky surface between crust and upper part of mantle
Rocky surface between upper and lower mantle
Ans. (c) Rocky surface between crust and upper mantle
Which of the following occurs due to tectonic shifts in the Earth’s lithosphere?
Tsunami
Volcano
Earthquake
All of the above
Ans. (d) All of the above
The interaction between Earth’s atmosphere, lithosphere, and hydrosphere are crucial for life on Earth. Each of them is responsible for essential pre-requisites for life, as we know it.
Some Interesting Facts About The Lithosphere
While the oceanic lithosphere is almost 170 million years old, certain parts of the continental lithosphere are considered to be about a billion years old.
The lithosphere is about 100 km thick. However, its thickness depends on its age, i.e., the older the lithosphere, the thicker it tends to be.
There is another name for the lithosphere; it is also known as the geosphere at times as it refers to all the rocks of the Earth.
The mafic crust along with the ultramafic mantle comprises the totality of the oceanic lithosphere.
Some of the most abundantly found elements in the lithosphere include oxygen, iron, silicon, and calcium.
Vedantu’s application can help students understand lithosphere and its composition in detail. We provide experienced teachers who are well versed with every physics and related topics.
FAQs on Lithosphere
1. What is the lithosphere in simple terms?
The lithosphere is the solid, rocky outer shell of the Earth. Think of it as the planet's hard skin. It includes the Earth's crust (both the land we walk on and the ocean floor) and the very top, rigid part of the mantle just below it.
2. What are the two main types of lithosphere?
The lithosphere is divided into two main types based on where it is found:
- Oceanic lithosphere: This is the part of the lithosphere that lies beneath the oceans. It is relatively thin and made of dense rock.
- Continental lithosphere: This is the lithosphere that makes up the continents. It is much thicker and less dense than its oceanic counterpart.
3. What are the main parts that make up the lithosphere?
The lithosphere is composed of two main parts layered on top of each other. The top layer is the Earth's crust, which is the outermost rocky surface. Right below the crust is the rigid upper portion of the mantle. Together, these two solid layers form the lithosphere.
4. Why is the lithosphere important for life on Earth?
The lithosphere is crucial for several reasons:
- It provides the solid surface where all terrestrial life, including humans, lives.
- The movement of its tectonic plates shapes our world by creating mountains, oceans, and continents.
- It is a rich source of essential minerals and resources, such as soil for farming and metals for industry.
- It plays a key role in the nutrient cycles that support all ecosystems.
5. What is the difference between the lithosphere and the asthenosphere?
The main difference lies in their physical state. The lithosphere is the cool, rigid, and brittle layer on top. The asthenosphere, which lies directly beneath the lithosphere, is a much hotter and more plastic-like layer of the mantle. Because it can slowly flow, the rigid lithospheric plates are able to move around on top of it.
6. Why is the oceanic lithosphere generally denser than the continental lithosphere?
This difference is mainly due to their rock composition. Oceanic crust is made of dense volcanic rock like basalt, while continental crust is made of lighter rocks like granite. Because it is denser, the oceanic lithosphere sits lower and forms the ocean basins, while the lighter continental lithosphere floats higher, forming the landmasses.
7. Can you give some real-world examples of the lithosphere?
Yes, you can see and interact with the lithosphere every day. Some common examples include:
- The ground you walk on, from grassy fields to city pavements.
- All the world's mountains, like the Himalayas and the Andes.
- The floor of the oceans, including deep trenches like the Mariana Trench.
- The rocks and soil that we use for agriculture and building materials.
8. How is the lithosphere related to the Earth's mantle? Is it the same thing?
No, the lithosphere is not the same as the mantle, but it includes a part of it. The mantle is a very thick layer of the Earth between the crust and the core. The lithosphere is made up of the crust AND the uppermost solid part of the mantle. The rest of the mantle below this solid section is hotter and can flow, so it is not considered part of the rigid lithosphere.
9. How do human activities like farming and building cities affect the lithosphere?
Human activities primarily affect the surface of the lithosphere, known as the crust. Farming can change the soil's composition and lead to erosion. Urbanisation, or the building of cities, covers large areas of land with concrete, which can alter natural water drainage and local ecosystems. Mining directly removes parts of the lithosphere to extract resources.
10. If the lithosphere is solid and rigid, how do tectonic plates move?
This is an excellent question. While the lithosphere itself is rigid, it is broken into large pieces called tectonic plates. These plates aren't fixed; they 'float' on the asthenosphere, a hotter, semi-fluid layer beneath them. The slow-moving currents within the asthenosphere act like a giant conveyor belt, pushing and pulling the rigid plates above, which causes earthquakes, volcanic activity, and the movement of continents.
