Interior of the Earth - Notes | Geography for UPSC 2024 (Pre & Mains) PDF Download

 Page 1


 
INTERIOR OF THE EARTH 
 
FORMATION OF THE INTERIOR 
 
Billions of years ago, the planetary blob that would become the Earth started 
out as a hot, viscous ball of rock.  
 
The heaviest material, mostly iron and nickel, sank to the center of the new 
planet and became its core. The molten material that surrounded the core was 
the early mantle. 
  
Over millions of years, the mantle cooled. Water trapped inside minerals 
erupted with lava, a process called “outgassing (release or give off (a 
substance) as a gas or vapour.)” .  
 
 Materials that initially stayed in their liquid phase during this process, called 
“incompatible elements,” ultimately became Earth’s brittle crust. 
 
PLANETARY DIFFERENCIATION: 
 
In planetary science, planetary differentiation is the process of separating out 
different constituents of a planetary body as a consequence of their physical or 
chemical behavior, where the body develops into compositionally distinct 
layers; the denser materials of a planet sink to the center, while less dense 
materials rise to the surface, generally in a magma ocean.  
 
Such a process tends to create a core and mantle. 
Page 2


 
INTERIOR OF THE EARTH 
 
FORMATION OF THE INTERIOR 
 
Billions of years ago, the planetary blob that would become the Earth started 
out as a hot, viscous ball of rock.  
 
The heaviest material, mostly iron and nickel, sank to the center of the new 
planet and became its core. The molten material that surrounded the core was 
the early mantle. 
  
Over millions of years, the mantle cooled. Water trapped inside minerals 
erupted with lava, a process called “outgassing (release or give off (a 
substance) as a gas or vapour.)” .  
 
 Materials that initially stayed in their liquid phase during this process, called 
“incompatible elements,” ultimately became Earth’s brittle crust. 
 
PLANETARY DIFFERENCIATION: 
 
In planetary science, planetary differentiation is the process of separating out 
different constituents of a planetary body as a consequence of their physical or 
chemical behavior, where the body develops into compositionally distinct 
layers; the denser materials of a planet sink to the center, while less dense 
materials rise to the surface, generally in a magma ocean.  
 
Such a process tends to create a core and mantle. 
 
     
 
 
EARTH’S LAYERS BASED ON CHEMICAL PROPERTIES 
1. CRUST 
2. MANTLE 
3. CORE 
 
        
 
 
Page 3


 
INTERIOR OF THE EARTH 
 
FORMATION OF THE INTERIOR 
 
Billions of years ago, the planetary blob that would become the Earth started 
out as a hot, viscous ball of rock.  
 
The heaviest material, mostly iron and nickel, sank to the center of the new 
planet and became its core. The molten material that surrounded the core was 
the early mantle. 
  
Over millions of years, the mantle cooled. Water trapped inside minerals 
erupted with lava, a process called “outgassing (release or give off (a 
substance) as a gas or vapour.)” .  
 
 Materials that initially stayed in their liquid phase during this process, called 
“incompatible elements,” ultimately became Earth’s brittle crust. 
 
PLANETARY DIFFERENCIATION: 
 
In planetary science, planetary differentiation is the process of separating out 
different constituents of a planetary body as a consequence of their physical or 
chemical behavior, where the body develops into compositionally distinct 
layers; the denser materials of a planet sink to the center, while less dense 
materials rise to the surface, generally in a magma ocean.  
 
Such a process tends to create a core and mantle. 
 
     
 
 
EARTH’S LAYERS BASED ON CHEMICAL PROPERTIES 
1. CRUST 
2. MANTLE 
3. CORE 
 
        
 
 
 
      
 
 
   
 
 
 
Page 4


 
INTERIOR OF THE EARTH 
 
FORMATION OF THE INTERIOR 
 
Billions of years ago, the planetary blob that would become the Earth started 
out as a hot, viscous ball of rock.  
 
The heaviest material, mostly iron and nickel, sank to the center of the new 
planet and became its core. The molten material that surrounded the core was 
the early mantle. 
  
Over millions of years, the mantle cooled. Water trapped inside minerals 
erupted with lava, a process called “outgassing (release or give off (a 
substance) as a gas or vapour.)” .  
 
 Materials that initially stayed in their liquid phase during this process, called 
“incompatible elements,” ultimately became Earth’s brittle crust. 
 
PLANETARY DIFFERENCIATION: 
 
In planetary science, planetary differentiation is the process of separating out 
different constituents of a planetary body as a consequence of their physical or 
chemical behavior, where the body develops into compositionally distinct 
layers; the denser materials of a planet sink to the center, while less dense 
materials rise to the surface, generally in a magma ocean.  
 
Such a process tends to create a core and mantle. 
 
     
 
 
EARTH’S LAYERS BASED ON CHEMICAL PROPERTIES 
1. CRUST 
2. MANTLE 
3. CORE 
 
        
 
 
 
      
 
 
   
 
 
 
 
    
 
 
EARTH’S LAYERS  
THE CRUST 
It is the outermost solid part of the earth. It is brittle in nature. The 
thickness of the crust varies under the oceanic and continental areas. 
Oceanic crust is thinner as compared to the continental crust. The mean 
thickness of oceanic crust is 5 km whereas that of the continental is around 
30 km. The continental crust is thicker in the areas of major mountain 
systems. It is as much as 70 km thick in the Himalayan region. 
It is 5-1.0 per cent of the earth’s volume. 
It is made up of heavier rocks having density of 3 g/cm3. 
Page 5


 
INTERIOR OF THE EARTH 
 
FORMATION OF THE INTERIOR 
 
Billions of years ago, the planetary blob that would become the Earth started 
out as a hot, viscous ball of rock.  
 
The heaviest material, mostly iron and nickel, sank to the center of the new 
planet and became its core. The molten material that surrounded the core was 
the early mantle. 
  
Over millions of years, the mantle cooled. Water trapped inside minerals 
erupted with lava, a process called “outgassing (release or give off (a 
substance) as a gas or vapour.)” .  
 
 Materials that initially stayed in their liquid phase during this process, called 
“incompatible elements,” ultimately became Earth’s brittle crust. 
 
PLANETARY DIFFERENCIATION: 
 
In planetary science, planetary differentiation is the process of separating out 
different constituents of a planetary body as a consequence of their physical or 
chemical behavior, where the body develops into compositionally distinct 
layers; the denser materials of a planet sink to the center, while less dense 
materials rise to the surface, generally in a magma ocean.  
 
Such a process tends to create a core and mantle. 
 
     
 
 
EARTH’S LAYERS BASED ON CHEMICAL PROPERTIES 
1. CRUST 
2. MANTLE 
3. CORE 
 
        
 
 
 
      
 
 
   
 
 
 
 
    
 
 
EARTH’S LAYERS  
THE CRUST 
It is the outermost solid part of the earth. It is brittle in nature. The 
thickness of the crust varies under the oceanic and continental areas. 
Oceanic crust is thinner as compared to the continental crust. The mean 
thickness of oceanic crust is 5 km whereas that of the continental is around 
30 km. The continental crust is thicker in the areas of major mountain 
systems. It is as much as 70 km thick in the Himalayan region. 
It is 5-1.0 per cent of the earth’s volume. 
It is made up of heavier rocks having density of 3 g/cm3. 
 
Crust comprises two distinct parts : 
 
OCEANIC CRUST 
This is thin layer of the earth that exists beneath the ocean basins. Oceanic 
crust, extending 5-10 kilometers (3-6 kilometers) beneath the ocean floor, is 
mostly composed of different types of basalts. Geologists often refer to the 
rocks of the oceanic crust as “sima.” Sima stands for silicate and magnesium, 
the most abundant minerals in oceanic crust. (Basalts are a sima rocks.) 
Oceanic crust is dense, almost 3 grams per cubic centimeter (1.7 ounces per 
cubic inch). 
  
Oceanic crust is constantly formed at mid-ocean ridges, where tectonic plates 
are tearing apart from each other. As magma that wells up from these rifts in 
Earth’s surface cools, it becomes young oceanic crust.  
  
Just as oceanic crust is formed at mid-ocean ridges, it is destroyed 
in subduction zones. Subduction is the important geologic process in which a 
tectonic plate made of dense lithospheric material melts or falls below a plate 
made of less-dense lithosphere at a convergent plate boundary.  
  
 Largely due to subduction, oceanic crust is much, much younger than 
continental crust.  
 
 
CONTINENTAL CRUST 
This is the thick layer of the earth that exists beneath the continents. 
Continental crust is mostly composed of different types of granites. Geologists 
often refer to the rocks of the continental crust as “sial.” Sial stands for silicate 
and aluminum, the most abundant minerals in continental crust. Sial can be 
much thicker than sima (as thick as 70 kilometers kilometers (44 miles)), but 
also slightly less dense (about 2.7 grams per cubic centimeter (1.6 ounces per 
cubic inch)).