Geographical diversity of India

Overview & Fundamental Concept

Pointwise AISSEE Class 9 Social Science guide for Geographical Diversity of India (Topic 1). Covers mainland coordinates, boundaries, Tropic of Cancer states, IST calculation, 6 physiographic relief zones, solved models, and 10 practice drills.

• Global Geographic Position: India lies entirely in the Northern and Eastern Hemispheres.
• Exact Mainland Coordinates:
  • Latitudinal Extent: Extends from 8°4' N (Kanyakumari, Tamil Nadu) in the south to 37°6' N (Indira Col, Ladakh) in the north.
  • Longitudinal Extent: Extends from 68°7' E (Ghuar Mota, Gujarat) in the west to 97°25' E (Kibithu, Arunachal Pradesh) in the east.
• Linear Dimensions & Total Area:
  • North to South Distance: Exactly 3,214 km.
  • East to West Distance: Exactly 2,933 km.
  • Total Geographical Area: 3.28 million sq. km (accounting for 2.4% of the world's total land area).
  • Global Rank: India is the 7th largest country in the world by land area (after Russia, Canada, USA, China, Brazil, and Australia).
• Land & Maritime Boundaries:
  • Land Frontier: Approximately 15,200 km.
  • Total Coastline: 7,516.6 km (including Andaman & Nicobar and Lakshadweep islands). Mainland coastline is ~6,100 km.
• The Tropic of Cancer (23°30' N): Divides the country into almost two equal latitudinal halves. Passes through 8 Indian States: Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand, West Bengal, Tripura, and Mizoram.

• The Longitudinal Time Gap:
  • The longitudinal difference between westernmost Gujarat (68°7' E) and easternmost Arunachal Pradesh (97°25' E) is roughly 30 degrees.
  • Since the Earth rotates 1° of longitude in 4 minutes ($360^circ / 24\text{ hrs} = 15^circ/\text{hr}$), the solar time difference between Arunachal Pradesh and Gujarat is:
  $$30^circ \times 4\text{ minutes} = 120\text{ minutes} = 2\text{ hours}$$.
  • The sun rises roughly two hours earlier in Arunachal Pradesh than in Gujarat.
• Standard Meridian of India:
  • To avoid nationwide confusion caused by having multiple local time zones, the meridian of 82°30' E (82.5° E) has been selected as the Standard Meridian of India.
  • Passes through Mirzapur (near Prayagraj, Uttar Pradesh).
  • The local time at this meridian is accepted as the Indian Standard Time (IST) for the entire nation.
  • IST is exactly 5 hours and 30 minutes ahead of Greenwich Mean Time (GMT +5:30).

• India is characterized by diverse geological relief features categorized into six broad divisions:
• 1. The Northern Mountains (Himalayas):
  • Young fold mountains extending from Indus to Brahmaputra (~2,400 km arc).
  • Three parallel longitudinal ranges:
    1. Great Himalayas / Inner Himalayas / Himadri: Highest continuous range (average height 6,000 m; contains Mt. Everest 8,848 m, Kanchenjunga 8,586 m). Perennially snowbound.
    2. Lesser Himalayas / Himachal: Rugged system (altitude 3,700 to 4,500 m; Pir Panjal is longest range; Dhaula Dhar, Mahabharat; famous hill stations: Shimla, Mussoorie, Nainital).
    3. Outer Himalayas / Shiwaliks: Outermost range (altitude 900 to 1,100 m; width 10-50 km; made of unconsolidated river sediments). Longitudinal valleys between Himachal and Shiwalik are called Duns (Dehradun, Kotlidun, Patlidun).
• 2. The Northern Plains:
  • Formed by the alluvial interplay of three major river systems: Indus, Ganga, and Brahmaputra along with their tributaries.
  • Highly fertile, agriculturally productive, flat terrain with dense population.
  • Morphological belts from north to south: Bhabar (narrow pebble belt where streams disappear), Terai (swampy, marshy, densely forested belt where streams re-emerge), Bhangar (older alluvium, contains calcareous kankar deposits), and Khadar (newer, younger alluvium renewed every flood season, intensely fertile).
• 3. The Peninsular Plateau:
  • Triangular tableland composed of old crystalline, igneous, and metamorphic rocks (part of Gondwanaland).
  • Two broad divisions: Central Highlands (north of Narmada, e.g., Malwa plateau, Chota Nagpur plateau) and Deccan Plateau (south of Narmada, triangular, sloping eastwards).
  • Bounded by Western Ghats (Sahyadris): continuous, higher average elevation (900-1,600 m), highest peak Anamudi (2,695 m); and Eastern Ghats: discontinuous, dissected by east-flowing rivers, average elevation 600 m, highest peak Mahendragiri (1,501 m).
• 4. The Indian Desert (Thar Desert):
  • Lies toward the western margins of the Aravalli Hills.
  • Undulating sandy plain covered with sand dunes; crescent-shaped dunes are called Barchans.
  • Arid climate, scanty rainfall (below 150 mm/year), low vegetation. Luni is the only prominent river in this region.
• 5. The Coastal Plains:
  • Western Coastal Plain: Narrow strip sandwiched between Western Ghats and Arabian Sea. Subdivided into Konkan (Mumbai to Goa), Kannad Plain (central stretch), and Malabar Coast (Kerala, noted for backwaters / kayals).
  • Eastern Coastal Plain: Wide and level plain along Bay of Bengal. Subdivided into Northern Circar (northern part) and Coromandel Coast (southern part). Features large deltas of Mahanadi, Godavari, Krishna, and Kaveri, and Chilika Lake (largest saltwater lake).
• 6. The Island Groups:
  • Lakshadweep Islands: Located in the Arabian Sea, close to Malabar coast. Composed of small coral islands (atolls). Total area 32 sq. km; administrative headquarters at Kavaratti Island. Uninhabited Pitti Island has a bird sanctuary.
  • Andaman and Nicobar Islands: Chain of islands located in the Bay of Bengal. Subdivided into Andaman (north) and Nicobar (south), separated by the Ten Degree Channel ($10^circ\text{ N}$). Formed by elevated submarine volcanic peaks. Barren Island in Nicobar contains India's only active volcano.