[Physics Class Notes] on Lithosphere Pdf for Exam

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.

1. Continental Lithosphere

2. 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 

1. What is the Lithosphere?

1. Rocky surface between crust and core

2. Rocky surface between mantle and crust

3. Rocky surface between crust and upper part of mantle

4. Rocky surface between upper and lower mantle

Ans. (c) Rocky surface between crust and upper mantle

2. Which of the following occurs due to tectonic shifts in the Earth’s lithosphere?

1. Tsunami

2. Volcano

3. Earthquake

4. 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. 

’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.