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 Meant by Lithosphere?
One can explain lithosphere as the outermost rocky terrain of Earth, consisting of crust and upper portion of the mantle.
2. What are the Types of Lithosphere?
You can divide lithosphere into two primary types – continental and oceanic.
3. What are the Two Layers of Lithosphere?
Crust is the top layer of lithosphere, comprising an outer rocky terrain. Upper mantle is the second layer just underneath this crust.
4. Define the lithosphere and discuss its types?
The word ‘litho’ has its origin from Greek vocabulary which literally means stone, and sphere refers to a globe. The lithosphere is basically the outermost surface of the Earth. It contains the upper part of Earth’s mantle as well as the crust of the same, which is brittle in nature.
There are two main types of lithosphere classified on the basis of where they exist:
The continental lithosphere: This is the layer that exists on the land, as a result of which, it covers all the continents and areas that are situated above sea level.
The oceanic lithosphere: This is the portion of the upper mantle and its crust that exist deep underneath the ocean.
5. What is the deepest part of the oceanic lithosphere? Why is the oceanic lithosphere denser than the continental lithosphere?
The Challenger Deep in the Mariana Trench is more than 11.5 km below sea level, rendering it the deepest part of the oceanic lithosphere.
This type of lithosphere tends to be denser than its counterpart, i.e., the continental lithosphere. This is mainly due to the fact that the oceanic lithosphere moves away from the mid-ocean ridge as it cools, thickens and ages. This phenomenon further leads to the process of thermal contraction because of which the oceanic lithosphere becomes denser.
6. Why is the lithosphere imperative?
There are a number of reasons as to why the lithosphere is vital for life on Earth:
The biosphere of Earth depends greatly on the rocky terrain of the lithosphere.
As the tectonic plates shift, they lead to the formation of volcanoes, mountains, and even continents.
It is a great source for the extraction of various valuable elements and minerals. For example, copper, magnesium, aluminium, calcium, etc.
Also, the lithosphere, biosphere, and hydrosphere are together responsible for providing animal life here on Earth with various nutrients.
7. What lies below the lithosphere? Explain in brief?
The asthenosphere, which is the part of Earth’s mantle, is the layer that lies underneath the lithosphere. It happens to extend from about 100-700 km below the Earth’s surface and is way more fluid and hotter than the lithosphere tends to be. But, as it is the ductile region of the Earth’s surface, it is also weaker than the lithosphere. It plays quite an important role with regard to the movement of the tectonic or lithospheric plates across the surface of the Earth.
8. How are humans harming the lithosphere and why is there a need to preserve it?
Activities like mining, farming, urbanisation, etc., tend to harm the lithosphere.
The lithosphere is the topmost crust of the Earth where the biosphere, i.e., us human beings and other living things tend to reside. And if the tectonic plates of the lithosphere didn’t move, there would be no change on our planet. This is why the lithosphere is so paramount to life on Earth.