Structure of the Earth | General Knowledge for Young Learners - Class 1 PDF Download

Layers of The Earth 

• Earth is the fifth largest planet in our solar system.
• It is the only planet that has been confirmed to support life.
• The planet has several layers, each with its own unique features.
• If we were to cut the planet in half, we would see that it is made up of multiple layers stacked on top of one another.

Why Does the Earth have Different Layers and How Are They Formed

•  During its formation, the Earth went through a process called differentiation. 
•  This process caused the heaviest elements to sink to the center of the Earth. 
•  At the same time, the lighter elements rose to the surface. 
•  As the Earth cooled down, it developed layers due to this separation of elements. 
•  The chemical composition of these elements helps define the internal layers of the Earth. 
•  Scientists learned about the different layers of the Earth by studying seismic waves. 
•  These seismic waves are produced by earthquakes and explosions. 
•  Seismic waves travel through the Earth and across its surface, helping researchers understand its structure. 

How Many Layers Does the Earth Have, and What Are They Called

Layers of the Earth

• The Earth's internal structure consists of three main layers: the crust, the mantle, and the core. 
• Both the mantle and the core are divided into smaller sections, creating a total of five distinct layers. 

• Chemical composition: The specific materials that make up each layer. 
• Physical properties: Features such as temperature, density, and state (solid or liquid). 
• Mechanical properties: How each layer behaves under stress or pressure. 

1. Crust
2. Upper Mantle
3. Lower Mantle
4. Outer Core
5. Inner Core

All the Earth’s Layers, Their Structure and Composition

1. Crust 

• Temperature: Ranges from 475 K (∼200°C) at the surface to 1300 K (∼1000°C) deeper down. 
• Thickness: Continental crust is about 25 miles (32 km) thick, while oceanic crust ranges from 3 to 5 miles (8 km) in thickness. 
• Density: Approximately 2830 kg/m³ for continental crust and around 3000 kg/m³ for oceanic crust. 

The crust is the outermost and thinnest layer of our planet and is less dense than the other layers. There are two types of crust:

Continental crust is thicker, made of granite rocks, and found near mountain ranges. Oceanic crust is thinner, composed of basalt, and located beneath the oceans.

• Abundant Elements: The most common elements in the earth's crust include oxygen, silicon, aluminum, iron, and calcium.
• Temperature and Pressure: The temperature within the crust is high enough to melt rocks, leading to the formation of the upper mantle, which lies beneath the crust.

2. Upper Mantle

• Temperature: Ranges from 1200 K (∼ 932°C) at the upper boundary with the crust to 1900 K (∼1652 °C) at the boundary with the lower mantle.
• Thickness: About 255 miles (410 km).
• Density: Approximately 3400 kg/m³.

The upper mantle is the largest and thickest layer of the Earth. Together with the crust, it forms the lithosphere, which is physically different from the layers below due to its lower temperature and high thickness.

• Below the lithosphere is the asthenosphere, a hotter and more malleable part of the upper mantle that extends from the bottom of the lithosphere to about 450 miles (700 km) deep.
• The composition of the upper mantle is not stable; it is always in motion, moving large areas of crust called tectonic plates. This movement causes the formation of volcanoes, mountains, and earthquakes.
• Between the upper and lower mantle, there is a transition zone that ranges in depth from 250 to 410 miles (410 to 660 km).

3. Lower Mantle

• Temperature: Ranges from 1900 K (∼ 1600°C) in the outer regions to as high as 4300 K (∼4000°C) at the bottom.
• Thickness: About 1,400 miles (2,250 km).
• Density: Approximately 4400 kg/m³.

The lower mantle is located below the upper mantle, extending from a depth of about 400 miles (650 km) down to 1,800 miles (2,900 km). It is incredibly large and makes up most of the Earth's volume.

• Due to its great depth, the temperature and pressure in the lower mantle are extremely high.
• Convection currents in the lower mantle allow heat from the Earth's interior to rise toward the surface.

4. Outer Core

• Temperature: Ranges from 4,300 K (4,030°C) in the outer regions to 6,000 K (5,730°C) closest to the inner core.
• Thickness: About 1,355 miles (2,180 km).
• Density: Between 9,900 and 12,200 kg/m³.

The outer core is located below the mantle and has a composition similar to the inner core, consisting of about 80% iron, along with nickel and some lighter elements.

• The outer core is very dense and exists in a viscous-liquid state because the pressure is not high enough to compress it into a solid.

5. Inner Core

• Temperature: Approximately 5,700 K (∼5,500°C).
• Thickness: About 760 miles (∼1,220 km).
• Density: Between 12,600 and 13,000 kg/m³.

The inner core is the center and the hottest part of the Earth. It is composed mainly of iron and nickel, with the highest density among all the Earth's layers.

• The inner core also contains metals such as gold, platinum, palladium, silver, and tungsten.
• Due to the extremely high temperature and pressure, the metals in the inner core change their structure and exist in a solid state.
• Recent discoveries suggest that the inner core itself is made up of two layers, separated by a transition zone that is about 150 to 250 miles (250 to 400 km) thick.