Introduction
We usually see the Earth from the outside. We see different types of landscape structures, plains, plateaus, grasslands, deserts, beaches, islands, forests or wildlife, etc. but have you ever wondered what can be found inside the Earth? All the things we see outside or use in our daily lives are formed because of the internal processes of the earth along with external factors. Here, we will be focusing on the inside of our Earth. We will learn about the rocks and minerals found inside our Earth, their uses, the classification of rocks, and various other related concepts.
These rocks and minerals are very useful for us and are used in various processes and products. These notes will serve the needs of students who are looking for Class 7 Geography Chapter 3 notes.
Rocks and Minerals
These are said to be building blocks of Earth which forms various kinds of landscapes on Earth as well as provide a number of resources as well. Rocks consist of minerals and these rocks are mined to extract minerals because these have Important properties and commercial value. There is no specific structure or chemical composition of rocks but minerals do have definite structure or other properties. Each rock can consist of one or more minerals. Rocks can be formed because of various geological processes and during these processes, various minerals get collected in one rock. When rocks are mined, these are called ores and the remaining rock after extraction of minerals is called tailing.
Uses of Rocks and Minerals
These are used in everyday life around us.
Rocks are used for making roads, buildings, and other construction purposes.
Some rocks which are precious are used as gemstones and some small rocks are also used in games as well.
Minerals are used for energy purposes such as coal, petroleum, etc. whereas others like fluorite, copper, talc, kaolinite, zinc, gold, diamond, etc. are used for making different kinds of products in the manufacturing industries from paper to jewellery products, minerals are used.
Difference Between Rocks and Minerals
Classification of Rocks
The various types of rocks are mentioned below.
Igneous Rocks
The rocks formed because of the solidification or cooling of the lava from the volcano are known as Igneous rocks. These are said to be the first and earliest rocks to be formed and other rocks are made from these rocks, thus these are also known as the primary rocks. These rocks are also considered magmatic rocks because of their formation from the magma or also called volcanic rocks because of the relationship with a volcano. These can be divided into the following two types:
Intrusive Igneous Rocks
These are those rocks that solidify under the crust of the Earth along with the presence of other existing rocks and it cools slowly and rocks become coarse-grained. The rocks which form deep in the crust and are coarse-grained are termed plutonic or abyssal rocks whereas the rocks which form under the crust but near the surface and are medium-grained are termed subvolcanic rocks or hypabyssal rocks.
Extrusive Igneous Rocks
The types of rocks which solidify above the crust of the Earth or on the surface outside are called extrusive Igneous rocks. Here, the process of cooking is not slow as compared to the intrusive one. They follow a quick solidification process because of the outside temperature present in the region thus, they are of fine quality and glassy texture.
Examples of Igneous Rocks
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The first image is of Basalt which is an example of extrusive Igneous rocks and is dark in colour and finely grained whereas the other image is of coarse-grained rock i.e Diorite which is an example of intrusive igneous rocks. Other examples are Dacite, Diabase, Gabbro, Obsidian, Granite, Peridotite, etc.
Sedimentary Rocks
These are the rocks that formed on or near the surface of the Earth because of geological processes such as erosion, weathering, dissolution, precipitation or lithification, etc. And usually have distinctive layers of bedding. They can be divided into three types:
Common Sedimentary Rocks
These sediments are carried in rivers or deposited in oceans or lakes and with time when the water disappears, the rock forms. Examples: sandstone, limestone, shale, etc.
Clastic Sedimentary Rocks
They are made up of clasts of the pre-existing rocks and the names of such rocks depend upon the size of the clast or grain.
Biologic Sedimentary Rocks
When a large number of living species die then such kinds of rocks form. Chert or limestone are formed in this way.
Examples of Sedimentary Rocks
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The first image is of limestone and another black one shale. Breccia, Chalk, Caliche, Chert, Conglomerate, Coal, Diatomite, Flint, limestone, etc. Are the other examples.
Metamorphic Rocks
These are the rocks that are formed from igneous or sedimentary rocks or even earlier metamorphic rocks which are formed due to high pressure, high heat, or other factors. The metamorphism process leads to the transformation of the existing rocks into another form. They are of three types:
Common Metamorphic Rocks
These include phyllite, schist, gneiss, quartzite, or marble.
Foliated Metamorphic Rocks
These are the rocks formed because of the parallel arrangement of certain minerals under pressure and are of platy or sheet-like structure.
Non- Foliated Metamorphic Rocks
They do not have platy or sheet-like structure and grains do not align even after having so much pressure.
Examples of Metamorphic Rocks
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The first image is of Gneiss and the other one is Anthracite. Other examples are Amphibolite, Hornfels, Marble, Lapis Lazuli, Novaculite, Quartzite, Soapstone, etc.
Rock Cycle
It is a cycle of various processes that lead to the formation and transformation of various types of rocks inside or outside the crust of the Earth. The three types of rocks which are formed are called igneous, sedimentary, and metamorphic due to various geological factors such as melting, cooling, heat or pressure, erosion, weathering, compacting and cementing, etc. When the heat and temperature inside the crust of the Earthrise, the magma forms which comes on the surface in the form of lava. When this lava hardened inside or outside the surface of the Earth becomes igneous rocks and when these igneous rocks erode into sediments because of various processes leads to the formation of sedimentary rocks and when these two rocks go under extreme pressure or other processes lead to the formation of metamorphic rocks which eventually are a transformation of already existing rocks. These metamorphic rocks can be eroded further to form sedimentary rocks or can be melted into magma. Thus this cycle continues and these rocks go on the interchange from one type of rock to another. Our earth has several favourable conditions which lead to the formation or interchangeability of these rocks such as wind, water, tectonic plates, and their movements, heat or pressure, subduction, etc.
So, now we have covered the facts about Earth and have seen what does happen inside it.
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Conclusion
Thus, here in this article, we have covered Chapter 3 of Class 7 Geography i.e. Inside our Earth. These notes will be useful for those who are in Class 7 or even the students of upper classes to understand the basic concepts. These will be helpful for those who find it difficult to read the chapter in the book and make notes out of it. Vedantu has eased your work by providing you with these crisp as well as comprehensive notes which will surely help you to understand the concepts properly as well as in revising the whole chapter quickly. You can check out notes of all other chapters or topics and other subjects as well on our website. These are created and prepared by the subject matter experts of Vedantu after thorough research to help you in your studies. We believe that these notes will surely help you to grow.
FAQs on Inside Our Earth
1. What is the inside of our Earth made of?
The Earth is made up of three main layers, much like an onion. The outermost layer is the crust, which is the thin surface we live on. Below that is the mantle, a very thick layer of hot, semi-solid rock. At the very centre is the core, which has an outer liquid part and an inner solid part, both made mostly of iron and nickel.
2. What are the three main types of rocks and how are they formed?
The three major types of rocks are defined by how they are formed:
- Igneous Rocks: These are formed when molten rock, called magma or lava, cools down and solidifies. Examples include granite and basalt.
- Sedimentary Rocks: These are formed from small particles of other rocks, shells, or dead plants that get pressed together over millions of years. Examples are sandstone and limestone.
- Metamorphic Rocks: These are formed when existing igneous or sedimentary rocks are changed by intense heat and pressure. For instance, limestone can turn into marble.
3. What is the main difference between a rock and a mineral?
The key difference is that a mineral is a naturally occurring substance with a definite chemical composition and structure. Think of it as a pure ingredient. A rock, on the other hand, is an aggregate or a mixture of one or more minerals. So, rocks are made of minerals, but minerals are not made of rocks.
4. How does the rock cycle work?
The rock cycle is a continuous process where rocks are created, changed, and destroyed. It works like this: Igneous rocks can be broken down into small pieces (sediments). These sediments can be compacted to form sedimentary rocks. If these rocks get buried deep under the Earth, heat and pressure can transform them into metamorphic rocks. If the heat is intense enough, any rock can melt back into magma and eventually cool to form a new igneous rock, starting the cycle again.
5. What are some common uses of rocks and minerals in our daily life?
We use rocks and minerals every day, often without realising it. For example:
- Rocks like granite and marble are used for building homes and making countertops. Sandstone is used in construction.
- Minerals like iron are used to make steel for cars and buildings. Salt (halite) is used in food, and quartz is used in watches and electronics.
6. Why can't we dig a hole to the centre of the Earth?
We cannot dig a hole to the Earth's centre because of the extreme conditions deep inside. As you go deeper, the temperature and pressure increase immensely. The mantle and core are so hot that they would melt any drilling equipment we have. The pressure is also strong enough to crush any machine or human long before reaching the centre.
7. What is the difference between magma and lava?
The difference is simply about location. Magma is the term for molten rock when it is still inside the Earth's crust. Once this molten rock erupts from a volcano and flows onto the surface, it is called lava. So, lava is just magma that has reached the Earth's surface.
