Earth and Its Natural Satellites (Part 1) Class 5 Notes Science

Introduction

•  Scientists think that about 5 billion years ago, our solar system was a swirling cloud of hot gas and dust. 
•  Most of the material in this cloud came together at the centre to create the Sun. 
•  In various other areas, the material also clumped together to form the planets. 
•  The Earth, the Sun, and the Moon are all part of our solar system. 
•  In addition to the Earth, there are seven other planets in our solar system. 

The Earth

• The Earth is the third planet in our solar system.
• It consists of air, water, and land.
• The Earth is surrounded by a layer of air known as the atmosphere.
• The atmosphere serves to protect us from the harmful ultraviolet rays emitted by the sun.

Internal Structure of the Earth

•  Imagine the Earth as a big surprise-filled chocolate! 
•  Just like chocolate has different layers – the outside shell, a soft centre, and maybe a crunchy piece inside – the Earth also has various layers. 
•  These layers are hidden deep below the surface we walk on. 
•  The first layer is the crust, which is where we live. 
•  Below the crust is the mantle, which is hot and gooey. 
•  At the centre of the Earth is the core, which is extremely hot, like a furnace! 
•  Each layer has an important job in keeping our planet just the way it is. 
•  Let’s explore these layers and see what makes the Earth so amazing from the inside out! 

1. Crust 

• The outer layer of the Earth is called the crust, and it is made up of rocks. 
•  Its thickness varies depending on where you are: it can be about 5 kilometres thick beneath the ocean floor. 
•  Under the continents, the crust can be as thick as 70 kilometres. 
•  This layer is where all the continents and oceans are found. 

2. Mantle 

•  It is located below the crust of the Earth and has a thickness of about 2900 km. 
•  The upper section of the mantle is made up of hard rocks, while the lower section consists of extremely hot, molten rocks. 
•  During a volcanic eruption, magma is released from this layer. 
•  This layer contains important elements like iron, magnesium, and aluminium. 

The crust and the outer mantle together form the tectonic plates, which move very slowly. The place where these plates touch each other is called a fault. When the plates move, they bump against each other. This is how an earthquake occurs.

3. Core 

• It is the innermost layer of the Earth.
• It has two sections: outer core and inner core.
• The outer core is approximately 2300 km thick and is made up of liquid iron and nickel.
• The inner core is around 1200 km thick and is a solid ball composed mainly of iron

The Sun

• The sun is a massive sphere made of hot, burning gases.
• It is located at the centre of the solar system.
• There is a thin layer of air around the sun called the corona.
• The sun is the closest star to Earth, situated about 150 million kilometres away.
• The main elements that make up the sun are hydrogen and helium.
• At the very centre of the sun is the core.
• The core is the hottest part of the sun.
• In the core, hydrogen atoms are transformed into helium, which releases a significant amount of heat and light energy.