Earth’s Internal Structure, Latitude & Longitude Explained | Useful for SSC, UPSC, Railway & Other Competitive Exams | Notes & MCQ.

Understanding the Earth’s internal structure, latitude, and longitude is essential for students preparing for competitive exams like SSC, UPSC, and Railway. These are fundamental concepts in geography that often appear in General Studies papers.

In simple terms, the Earth is divided into three main layers: crust, mantle, and core.

To locate any place on Earth, we use a grid system made up of latitude and longitude lines.

In this post, you’ll learn each topic in simple language, supported by real-life examples, clear diagrams, and revision notes. Whether you're just starting or revising before the exam, this blog will help you understand the geography basics better. Let’s begin!

 

 🌍 Earth

🧱 Internal Structure of the Earth

The Earth is made up of three main layers:

1. Crust (Outer Layer):

1.    Earth’s outer layer.

2.    It's the thinnest layer.

3.    Thickness = 30 kms.

4.    Made of SIAL = Silicon & Aluminium.

5.    Divided into continental crust (land) and oceanic crust (under oceans).

Example:
The soil and mountains you see around you are part of the crust.

2. Mantle (Middle Layer):

1.    Thicker than the crust.

2.    Made up of SIMA = Silicon & Magnesium.

3.    Magma present in this.

4.    Movements in the mantle cause earthquakes and volcanic eruptions.

Example:
During an earthquake, the shaking occurs due to movement in the mantle.

3. Core (Inner Layer): Also called Barysphere.

1.    Divided into outer core (liquid) and inner core (solid).

2.    Made up of NIFE = Nickel & iron.

3.    Generates Earth’s magnetic field.

Example:
The compass points north due to Earth’s magnetic field, which comes from the core.

 

Read Article on Galaxy, Universe & Earth.

 

Discontinuity of Earth

 

Conrod Discontinuity : Between upper crust and lower crust.
Moho Discontinuity : Between lower crust and upper mantle.
Repetti Discontinuity : Between upper mantle and lower mantle.
Guttenberg Discontinuity : Between lower mantle and upper core.
Lehman Discontinuity : Between upper core and lower core.

Solar System Full Details: Notes & MCQ.

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📏 What is Latitude?
(It refers to Location)

1.   Lines that run horizontally on the globe.

2.   Measure how far north or south a place is from the Equator (0° Latitude).

3.   Range: 0° to 90° North and 0° to 90° South

Significant Latitude:
#Equator (0°)

#Tropic of Cancer (23.5° N)

#Tropic of Capricorn (23.5° S)

#Arctic Circle (66.5° N)

#Antarctic Circle (66.5° S)

#North Pole (90° N), South Pole (90° S)

#India is located between 8°N to 37°N latitude.

🌐 What is Longitude?
(It refers Time Zone)

• Lines that run vertically on the globe.
• Measure how far east or west a place is from the Prime Meridian (0° Longitude).
• Range: 0° to 180° East and 0° to 180° West

Important Longitude:

• Prime Meridian (0°): Passes through Greenwich, England.
• Indian Standard Time is based on 82.5° E longitude.

Example:
-Time difference between India and London is due to their longitude difference.

- Earth Rotate 1° in 4 minute & 15° in 1 Hour.

Exam Tip:
Maximum Time Zone in Country – France (13), Russia (11), USA (6).

 
Preamble of the Indian Constitution.

 

Difference Between Latitude and Longitude:

Feature	Latitude	Longitude
Direction	Horizontal (East–West)	Vertical (North–South)
Measures	North–South from Equator	East–West from Prime Meridian
Range	0° to 90° (N & S)	0° to 180° (E & W)
Reference Line	Equator	Prime Meridian
Purpose	Climate Zones	Time Calculation

Countries Located on Tropic of Cancer:

North America: Bahamas, Mexico.
Africa: Libia, Niger, Algeria, Mali, West Sahara, Maritania.
Asia: Taiwan, China, India, Bangladesh, Myanmaar, Oman, UAE, Saudi Arab.
Indian Ocean, Atlantic Ocean, Pacific Ocean, Taiwan Strait, Red Sea, Bay of Mexico.

Countries Located on Tropic of Capricorn:

South America: Argentina, Brazil, Chile, Praguay.
Africa: Namibia, Botswana, South Africa, Mozambeque, Madagascar, Australia.
Indian Ocean, Atlantic Ocean, Pacific Ocean.

Countries Located on Equator:

Equador, Colombia, Brazil, Gabon, Congo, Yuganda, Kenya, Saotom & Princep, Somalia, Maldives, Indonesia.
Indian Ocean, Atlantic Ocean, Pacific Ocean.

Equinox:
Days when the sun is exactly above the equator which makes day and night equal.
-Vernal Equinox on 21^st March.
-Autumnal Equinox on 23^rd September.
-Neither of the poles is tilted towards sun.
-Shortest day of year is 22^nd December, termed as Winter Solstice.

 

Attempt MCQ Quiz:

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