Important Points About the Interior Structure of the Earth - Study Notes

Interior Structure of the Earth: Today, we will be covering another important topic for or the General Awareness Section of SSC, Railway and other exams.

Earth has a diameter of about 12756 km at the equator & about 12715 km at the poles. The earth's interior is separated into three layers: crust, mantle, and core. The crust is the earth's outermost layer, while the core is the earth's deepest layer, located at a depth of 2900 kilometers. This article provides a quick overview of the earth's three inner layers.

Interior Structure of the Earth: Today, we will be covering another important topic for or the General Awareness Section of SSC, Railway and other exams.

Earth has a diameter of about 12756 km at the equator & about 12715 km at the poles. The earth's interior is separated into three layers: crust, mantle, and core. The crust is the earth's outermost layer, while the core is the earth's deepest layer, located at a depth of 2900 kilometers. This article provides a quick overview of the earth's three inner layers.

Interior Structure of Earth

Image Source: OSweetNature/Shutterstock and astronomy.com

First Layer - Crust 

• It is the earth's outermost solid layer, which is typically 8-40 km thick.
• It has a fragile structure.
• The crust accounts for about 1% of the earth's volume and 0.5 percent of its mass.
• The thickness of the crust differs between oceanic and continental areas. The oceanic crust is thinner (approximately 5km) than the continental crust (about 30kms).
• Because the major component parts of the crust are silica (Si) and aluminium (Al), it is sometimes referred to as SIAL (Sometimes SIAL is used to refer to Lithosphere, which is the region comprising the crust and uppermost solid mantle, also).
• The materials in the crust have a mean density of 3g/cm3.
• The Conrad Discontinuity is the separation between the hydrosphere and the crust.

Second Layer - Mantle

• The mantle is the region of the interior that extends beyond the crust.
• The Mohorovich Discontinuity, or Moho discontinuity, is the boundary between the crust and the mantle.
• The thickness of the mantle is approximately 2900 kilometers.
• The mantle accounts for around 84 percent of the earth's volume and 67 percent of its mass.
• Because silicon and magnesium are key component elements of the mantle, it is also known as SIMA.
• The layer has a greater density than the crust, ranging from 3.3 to 5.4g/cm3.
• The Lithosphere is made up of the topmost solid component of the mantle as well as the whole crust.
• The asthenosphere (80-200km) is a very viscous, mechanically weak, and ductile upper mantle deforming zone located directly below the lithosphere.
  The asthenosphere is the primary source of magma and the layer through which the lithospheric/continental plates move (plate tectonics).
• Repetti Discontinuity refers to the transition between the upper and lower mantles.
• Mesosphere refers to the region of the mantle that is just below the lithosphere and asthenosphere but above the core.

Third Layer - Core

• It is the deepest layer that surrounds the earth's core.
• Guttenberg's Discontinuity separates the core from the mantle.
• Because it is mostly constituted of iron (Fe) and nickel (Ni), it is also known as NIFE.
• The Lehmann Discontinuity is the separation between the upper and lower cores.
• The term "barysphere" can apply to either the core of the planet or its whole interior.
• The core accounts for almost 15% of the earth's volume and 32.5 percent of its mass.
• The core is the earth's densest layer, with a density ranging from 9.5 to 14.5g/cm3.

Interior Structure of Earth - Summary

Parameters	Crust	Mantle	Core
Relative Position	Outermost layer Thinnest Layer under the ocean, thickest under continents Crust and top of mantle is called lithosphere	Middle layer Thickest layer Top portion is called asthenosphere	Inner layer Consists of the Inner core and outer core
Composition	Solid rock, Mostly Silicon and Oxygen Oceanic Crust – Basalt Continental Crust - Granite	Hot softened Rock Contains Iron and Magnesium	Mostly Iron and Nickel Outer Core- Soft flowing liquid Inner Core - solid
Density (grams/cubic centimetre)	Least dense layer overall Oceanic crust is more dense than continental crust (2.7)	Density increases with depth as pressure increases with depth (3.5 – 5.5)	Heaviest material therefore most dense layer (10 – 12)
Representative Chemical Composition	SiO2	(Fe, Mg) SiO4	Fe, Ni
Temperature (Kelvin)	300-500	500-3,000	3,000 – 5,300
Pressure (Atmosphere)	1 – 1,000	103 - 106	106– 107

Change in Temperature, Density, and Pressure with the Depth of Earth

• The temperature rises with increasing depth as observed in mines.
• The temperature rises as one moves from the earth's surface to the center. But, the rate of temperature rise under the surface is decreasing towards the center 
• Pressure is rising from the earth's surface to its core, just as it is rising in temperature. It is owing to the enormous weight of the overlaying elements, such as rocks.
• Because of the immense pressure of the surrounding layers, the materials in the center of the planet are solid even at such high temperatures.
• The density of the earth's layers increases towards the center due to increased pressure and the presence of heavier minerals such as nickel and iron.

All The Best !!!