CBSE Class 7 Social Science Geography Revision Notes Chapter 3

CBSE Class 7 Geography Chapter 2 Notes – Inside our Earth

Students will gain knowledge of what is inside our Earth through Class 7 Social Science Geography Chapter 2 Notes. It covers in detail a comprehensive understanding of the Interior of the Earth, Rocks and Minerals and their types, etc. 

Chapter 2 of Class 7 Geography Inside Our Earth contains a variety of interesting topics that help students grasp the concept of the Earth’s interior. There are numerous topics of interest, including rocks found on Earth, minerals, the interior of our planet, and much more.

Students must understand these facts about the planet’s interior because these concepts are important from an exam perspective. Extramarks Class 7 Geography Chapter 2 Notes aid in understanding the concepts of the chapter, with which, students can answer and clear any doubts they may have.

Inside our Earth – Class 7 Geography Chapter 2 Notes

Access CBSE Class 7 Social Science Geography Chapter 2 – Inside Our Earth

2. Layers of Earth

Take a cabbage as an example to understand the Earth’s layers. When cabbage is cut vertically, layers of leaves are visible before the extreme core part. The structure is similar to that of Earth.

The Earth is made up of three layers:

Crust

• The Earth’s surface outermost layer
• It is primarily composed of silicate. Its thickness can range from 5 km in the oceanic crust to 35 km in the continental crust.
• This crust is composed of sedimentary material, and beneath it are acidic crystalline, igneous, and metamorphic rocks.
• Continents cover the crust and are made up of lighter silicates, which is a silica and aluminium mixture.
• The ocean crust, on the other hand, is composed of heavier silicates, i.e., Silica + Magnesium (Sima).
• The crust covers about 1% of the Earth’s total volume.

Mantle

• The mantle is found beneath the crust and is approximately 2,900 km thick.
• It takes up 84% of the Earth’s volume and contains approximately 66% of the Earth’s mass.
• It is rich in iron and magnesium-rich silicate.
• The temperature rises from 2,000 degrees Celsius to 40,000 degrees Celsius as one moves closer to the centre.
• The high temperature causes the silicate material to relax without changing its properties.
• The heat generated in the mantle region causes the material to be transferred in different directions, resulting in the formation of the Earth’s landscape. It also causes tectonic plate movement, which results in volcanic eruptions, earthquakes, seabed movement, and mountain formation.

Core

•  The Earth’s core is more like a furnace from which enormous heat and pressure flow out, creating the geothermal gradient.
• The core is made up of iron and nickel. 
• The core is divided into two parts: the liquid outer core and the solid inner core. The Earth’s magnetic field is created and maintained by the churning of this liquid portion. The inner core, on the other hand, is extremely hot and a dense ball of iron. Inside this region, the density and pressure prevent the iron from melting.

3. Rocks and Minerals

A rock is a mineral mixture that is tightly held together in a solid form. They occur in nature. They can be classified based on their formation into the following.

1. Igneous rock is a type of rock formed by the solidification of lava or magma. Magma is formed by the melting of rocks found in the mantle or crust. It is classified into two types.

• Intrusive or Plutonic Rock: It refers to the rocks formed when magma cools and crystallises within the Earth’s crust. The mineral granite is an example of plutonic rock.
• Extrusive or Volcanic Rock: It refers to the rocks formed by the cooling of magma after emerging from beneath the Earth’s surface as a thick semi-solid form similar to lava. For instance, pumice or basalt rock.

4. Sedimentary rocks form in water as a result of the accumulation and cementation of very small pieces of broken rocks, minerals, and organisms. For example, sandstone, limestone, and shale. Sedimentary rocks frequently contain fossils.
5. Metamorphic rock occurs when sedimentary or igneous rocks are subjected to high pressure and temperature conditions, causing changes in their physical properties and chemical composition. This is referred to as metamorphism. Quartzite, marble, and other similar materials are examples of this.

6. Minerals

Minerals are naturally occurring elements or compounds with specific physical properties and distinct chemical compositions. They are extremely beneficial to humans. Minerals can be used as fuels (e.g., coal), natural gas, and petroleum, as well as in industries to form iron, aluminium, gold, and uranium. They can also be used as fertilisers and mineral raw materials.

Class 7 Social Science Geography Chapter 2 Inside Our Earth Notes

An Overview of The Earth

Earth has the potential to be a very dynamic planet. There are so many changes happening all the time, both outside and inside the Earth. The interior of the Earth is made up of three distinct layers. The layers are referred to as the crust, mantle, and core. The majority of rocks are found in the Earth’s crust. The three main categories of rocks are igneous, sedimentary, and metamorphic rocks. Most minerals are found naturally and have some physical properties as well as chemical composition. Inside our Earth Class 7 Notes cover these concepts in-depth which will help students understand these topics and achieve more marks. 

A Look into The Earth’s Interior

There are numerous layers that overlap one another that make up the Earth. These concentric layers are nested within one another. The crust is the topmost layer, and it is the thinnest of all. The crust is made up of 35km of landmasses and only 5 km of ocean floors. Alumina and silica are the constituents that make up the majority of the continental landmasses on the crust. As a result, it is known as SiAl. Magnesium and silica are two minerals that constitute ocean masses. As a result, it is known as SiMa. 

The mantle is the layer that lies beneath the earth’s crust. The depth of the entire mantle layer is approximately 2,900 km beneath the Earth’s surface. The layer beneath the mantle is known as the core, and it is the deepest. The core’s total radius is approximately 3,500 km. As a result, it is unquestionably the largest of the layers. The main materials found in the core are iron and nickel, which is referred to as NiFe. The core has a very high temperature and pressure. Class 7 Geography Chapter 2 Notes cover more details about the various layers of the Earth’s interior.

Different Rocks and Minerals

A rock is any particular natural mass composed of mineral matter. The purpose of rocks is to cover the earth’s crust. Rocks come in a variety of sizes, colours, and textures.

The Earth’s crust is made up of many different types of rocks that make up the entire layer. These rocks will be classified into major groups.

1. Igneous Rocks

These rocks form as a result of magma cooling. These rocks are formed when magma solidifies. Igneous rocks are primary rocks. They can be classified into Intrusive and Extrusive Igneous Rocks. 

• Intrusive Igneous Rocks: These are the rocks that form deep within the Earth’s crust as a result of magma cooling. For example, Granite. This rock is used in the manufacture of grinding stones.
• Extrusive Igneous Rocks: These rocks form on the Earth’s surface as a result of magma cooling immediately after it emerges. For example, Basalt. It is said that the entire Deccan plateau is made up of basalt rocks.

2. Sedimentary Rocks

These are the rocks that form after falling, colliding, and cracking into smaller fragments. These fragments are referred to as sediments, and they are transported and deposited at a specific location by water and wind. For example, sandstone.

3. Metamorphic Rocks

When subjected to high pressure and heat, sedimentary and igneous rocks frequently transform into metamorphic rocks. For example, limestone transformed into marble and clay transformed into slate.

The rock cycle refers to the entire process by which rocks change form from one form to another. Extramarks Inside our Earth Class 7 Chapter 2 Notes provide explanations of the rock cycle and procedures in simple language that allow students to quickly grasp these concepts.