India: Geographical Features

• Reason for Selection:
1. India has a vast longitudinal breadth of roughly $30^{\circ}$ ($68^{\circ}7'\text{E}$ in Gujarat to $97^{\circ}25'\text{E}$ in Arunachal Pradesh).
2. Because Earth rotates $1^{\circ}$ in 4 minutes, there is a two-hour real local solar time difference ($30 \times 4 = 120\text{ minutes}$) between the eastern and western extremities of India.
3. To prevent confusion in train schedules, broadcast timetables, and flight departures, the central meridian $82^{\circ}30'\text{E}$ (passing through Mirzapur near Prayagraj) was selected as the uniform Standard Meridian for the entire country.
• Time Difference from GMT:

$$\text{Time Difference} = 82.5^{\circ} \times 4\text{ minutes} = 330\text{ minutes} = \mathbf{+5\text{ hours } 30\text{ minutes ahead of GMT}}$$

.

1. Greater Himalayas (Himadri):
   • The northernmost and highest continuous range with average elevation $> 6,000\text{ meters}$.
   • Permanently snow-clad; contains the world's loftiest peaks: Mount Everest ($8,848.86\text{ m}$) and Kanchenjunga ($8,586\text{ m}$).
   2. Lesser Himalayas (Himachal):
   • Lies south of Himadri; average elevation $3,700 - 4,500\text{ meters}$.
   • Contains rugged ranges (Pir Panjal, Dhauladhar) and world-famous hill stations: Shimla, Mussoorie, Nainital, Darjeeling.
   3. Outer Himalayas (Shiwaliks):
   • The southernmost low-lying foothills with average elevation $900 - 1,100\text{ meters}$.
   • Composed of unconsolidated river gravel and alluvium; separated from Himachal by flat structural valleys called "Duns" (e.g., Dehradun).

• Bhangar:
1. The older alluvium deposited in higher terrace regions away from modern riverbeds.
2. Lies above the reach of regular annual monsoonal floods.
3. Darker in color, less fertile, and contains hard calcareous calcium carbonate nodules called Kankar.
• Khadar:
1. The newer, younger alluvium deposited on the low-lying active floodplains along river courses.
2. Renewed almost every year by annual monsoon flood waters.
3. Extremely fine-grained, light-colored, porous, and exceptionally fertile, ideal for intensive agricultural cropping.

1. Continuity: Western Ghats form a continuous, unbroken mountain barrier that can be crossed only through mountain passes (Thal Ghat, Bhor Ghat, Pal Ghat); Eastern Ghats are discontinuous, fragmented, and dissected into isolated hills by major east-flowing rivers (Godavari, Krishna, Cauvery).
   2. Average Elevation: Western Ghats are much higher (average $900 - 1,600\text{ meters}$); Eastern Ghats are lower (average $\approx 600\text{ meters}$).
   3. Highest Peak: Western Ghats peak is Anamudi ($2,695\text{ m}$) in Kerala; Eastern Ghats peak is Jindhagada / Mahendragiri ($1,501\text{ m}$).
   4. Rainfall: Western slopes of Western Ghats receive heavy orographic rainfall ($> 250\text{ cm}$) from the southwest monsoon; Eastern Ghats receive moderate rainfall.

• Himalayan Rivers:
1. Perennial Rivers: Fed by both melting glacial snow and seasonal monsoon rains, flowing continuously throughout the year.
2. Long courses with high erosional energy, forming deep V-shaped gorges, waterfalls, and massive fertile deltas.
Examples: Ganga, Indus, Brahmaputra.
• Peninsular Rivers:
1. Non-Perennial (Seasonal) Rivers: Dependent entirely on seasonal monsoon rainfall; flow decreases drastically or dries into trickles during summer.
2. Shorter, shallower, mature graded valleys with gentle gradients.
Examples: Godavari, Krishna, Cauvery, Narmada.

• The Bhabar Belt: A narrow, sloping strip of land ($8\text{ to } 16\text{ km}$ wide) running parallel to the Shiwalik foothills in the Northern Plains.
• It is composed of unassorted heavy sediments, coarse gravel, pebbles, and boulders washed down by swift Himalayan mountain streams.
• Unique Hydrological Phenomenon:
Due to the extreme porosity and high permeability of the loose boulder beds, all streams and rivers sink and disappear completely underground, leaving a dry surface riverbed! The subterranean water re-emerges further south in the wet Terai zone.

• 1. Lakshadweep Islands: Located in the Arabian Sea off the Malabar coast.
Geological Origin: Coral Origin; formed entirely from the accumulation of calcium carbonate skeletons of tiny marine coral polyps, creating beautiful coral atolls and ring reefs.
• 2. Andaman and Nicobar Islands: Located in the Bay of Bengal.
Geological Origin: Volcanic / Submarine Tectonic Origin; they are the elevated summits of submerged tertiary submarine mountain ranges (extension of the Arakan Yoma of Myanmar). Contains Barren Island, India's only active volcano.

• The general slope of the Peninsular plateau of India tilts from west to east, which is why rivers like Godavari, Krishna, and Cauvery flow eastward into the Bay of Bengal.
• Narmada and Tapi are Geological Exceptions:
1. They do not flow over the general surface slope of the plateau.
2. They flow through linear, down-faulted tectonic Rift Valleys (Graben) formed by faulting between the Vindhya and Satpura mountain ranges.
3. The structural tilt of these rift valleys slopes from east to west, carrying the rivers west into the Arabian Sea, where they form Estuaries instead of deltas.