Peninsular Plateau

Topic: Structure and Physiography of India: Himalayas, Plains, Peninsula, Coasts and Islands · NCERT: Class 7, Ch 1 "Geographical Diversity of India"; Class 11, Ch 2 "Structure and Physiography"

Meaning

The Peninsular Plateau is a large, raised block of very old, hard rock that covers most of central and south India. It is shaped like an irregular triangle and rises from about 150 m above the river plains to 600-900 m. It matters because it is one of India's oldest and most stable landmasses. Its slope, rocks and faults decide which way the big rivers flow, where black soil and coal are found, and where earthquakes can still happen.

Explanation

How it formed: an old block that has still moved

• Origin: the plateau is part of the ancient Archaean block. Archaean means rocks formed more than 2.5 billion years ago.

• This block was once part of the old southern supercontinent Gondwana.

• Shaped by later movements: the plateau has gone through repeated uplift, sinking (submergence), faulting and fracturing.

• Uplift pushed up block mountains. A block mountain is a block of land raised between two faults (breaks in the Earth's crust).
• Faulting made rift valleys. A rift valley is a long, narrow valley that sank between two parallel faults. Examples are the Narmada, Tapi and Damodar.

• Fracturing opened cracks. Lava flowed out through some of them, and molten rock filled others to form dykes.

• Not fully quake-free: the Bhima fault, along the Bhima river (a Krishna tributary, Maharashtra–Karnataka), is still seismically active. This means earthquakes can happen there.

Limits and parts

• Outer limits:
• North-west: the Delhi ridge, the low, rocky northern tip of the Aravallis (Delhi).
• East: the Rajmahal hills (Jharkhand).
• West: the Gir range (Saurashtra, Gujarat).

• South: the Cardamom hills (Kerala–Tamil Nadu).

• North-east extension: the Meghalaya (Shillong) plateau and Karbi Anglong (Assam) belong to the same old block.

• They are cut off from the main plateau by the Malda gap. This is a low area made by faulting between the Rajmahal hills and the Meghalaya plateau. Rivers later filled it with silt.

• Two main parts, divided roughly by the Narmada:

• Central Highlands: the part north of the Narmada. It is 700-1,000 m high and covers most of the Malwa plateau.

• Deccan: the part to the south. The Satpura range forms its northern edge.

• Patland plateaus: flat-topped, step-like surfaces at different heights. Long erosion has worn the land down to level tops.

• Examples: Hazaribagh, Palamu, Ranchi (Jharkhand), Malwa (Madhya Pradesh), Coimbatore (Tamil Nadu) and the Karnataka plateau.
• In Chotanagpur, these flat tops are called pats (e.g. Netarhat pat).

Slope and drainage

• General slope: west to east.
• The Western Ghats edge is high. The land falls gently towards the Bay of Bengal.

• So the Mahanadi, Godavari, Krishna and Kaveri flow east and form deltas.

• Exceptions: the Narmada and Tapi flow west into the Arabian Sea.

• They run through rift valleys, not down the general slope.

• They form estuaries (wide river mouths where river and sea water mix), not deltas.

• Central Highlands slope north and north-east.

• So the Chambal, Betwa, Ken and Son flow north or north-east to the Yamuna and Ganga.

Typical landforms and soils

Landform	Simple meaning	How it forms
Tor	A pile of rounded rock blocks standing on bare rock	Granite weathers along its cracks → the soft parts wash away → hard rounded blocks are left standing
Block mountain	Land raised between two faults	The crust breaks → one block is pushed up, or the sides sink
Rift valley	A sunken valley between parallel faults	The crust stretches and breaks → the middle block drops
Spur	A ridge sticking out from a hillside	Rivers cut valleys on both sides of a ridge
Hummocky hill	Low, rounded, uneven hills	Long weathering and erosion of old rock
Bare rocky structure	Exposed rock with little soil	Erosion removes the soil
Quartzite dyke	A wall-like band of hard rock	Molten rock fills a crack and cools; it resists erosion and stands out like a wall

• Dykes act like natural dam walls. Water collects behind them, so they make good natural water-storage sites.
• Black soil (regur): it covers the west and north-west of the plateau.
• It forms from weathered basalt lava of the Deccan Traps.
• It holds moisture well and suits cotton.

Where it occurs

• Main plateau: most of south and central India, from the Delhi ridge (Delhi) to the Cardamom hills (Kerala–Tamil Nadu), and from the Gir range (Gujarat) to the Rajmahal hills (Jharkhand).
• Central Highlands units:
• Malwa plateau (western MP): a lava plateau; the Chambal rises near Mhow.
• Vindhyan range (MP): an escarpment (a long, steep, cliff-like slope) north of the Narmada rift.
• Bundelkhand (UP–MP border) and Baghelkhand (north-east MP).

• Aravalli range (Gujarat → Rajasthan → Haryana → Delhi): the western edge.

• Satpura range (MP–Maharashtra): between the Narmada and the Tapi; its highest point is Dhupgarh (~1,350 m), near Pachmarhi.

• Maikal range (MP–Chhattisgarh): its Amarkantak plateau is the source of both the Narmada and the Son.
• Chotanagpur plateau (Jharkhand, extending into Chhattisgarh, Odisha, West Bengal and Bihar): made up of the Hazaribagh, Ranchi and Palamu plateaus.
• It is India's richest mineral store: coal, iron ore, mica and bauxite.
• Its highest peak is Parasnath (~1,365 m).

• Its Damodar rift holds the Jharia, Bokaro and Raniganj coalfields.

• North-east outliers: the Shillong (Meghalaya) and Karbi Anglong (Assam) plateaus.

• Rift valleys: the Narmada, Tapi and Damodar.
• Active fault: the Bhima fault (Maharashtra–Karnataka).
• Ravines: the Chambal badlands in Bhind and Morena (MP) and Dholpur (Rajasthan).

Don't confuse with

• Central Highlands: this is only the part of the Peninsular Plateau north of the Narmada. It slopes north and north-east, while the plateau as a whole slopes west to east.
• Himalayas: they are young fold mountains from the Tertiary period. The Peninsular Plateau is an old, stable Archaean block of Gondwana origin.
• Delta-forming east-flowing rivers vs Narmada–Tapi: the Mahanadi, Godavari, Krishna and Kaveri follow the general slope and form deltas. The Narmada and Tapi flow west through rift valleys and form estuaries.
• Patland plateau vs lava plateau: a patland is a set of flat, step-like surfaces made by long erosion (Chotanagpur pats). A lava plateau, such as Malwa, is covered by Deccan basalt.

Prelims Hooks

• Limits: Delhi ridge (NW), Rajmahal hills (E), Gir range (W), Cardamom hills (S). Shillong and Karbi Anglong are the north-eastern extensions, separated by the Malda gap.
• Slope: the plateau slopes west → east, but the Central Highlands slope north and north-east.
• Rift-valley rivers: Narmada, Tapi and Damodar. The Narmada and Tapi flow west and form estuaries.
• North → south order: Vindhya → Narmada → Satpura → Tapi.
• Highest points: Guru Shikhar (Aravalli, ~1,722 m) > Parasnath (Chotanagpur, ~1,365 m) > Dhupgarh (Satpura, ~1,350 m).
• Trap: the "stable" plateau still has an active fault: the Bhima fault (Maharashtra–Karnataka).

Mains Points

• Old and stable, but not inert (GS-I):
• The plateau is an Archaean block, yet repeated uplift, faulting and fracturing made its rift valleys (Narmada, Tapi, Damodar), block mountains and dykes.
• The active Bhima fault shows that peninsular India still faces earthquake risk.

• So planning for dams and cities must take this risk into account.

• Landforms drive resources (GS-I/III):

• Deccan basalt → black soil → the Malwa and Maharashtra cotton-soybean belt.
• Gondwana rocks in the Chotanagpur rift troughs → coal, iron ore, mica and bauxite → steel and power industries.

• Quartzite dykes give natural sites for storing water.

• Land degradation on the plateau's north-western edge (GS-III):

• Chambal ravines: gullies cut into soft alluvium destroy farmland every year. Responses include plugging gullies, building check dams and planting trees.
• Aravallis: mining opens gaps in the range → Thar dust reaches Delhi-NCR. The Aravalli Green Wall Project (2023) aims to green a 5 km buffer across 29 districts in Delhi, Haryana, Rajasthan and Gujarat [2].

Related concepts

• Patland plateau
• Chambal ravines
• Central Highlands
• Aravalli Range
• Delhi ridge
• Malwa plateau
• Vindhyan range
• Satpura range
• Maikal range
• Gir range

Read more

• The Peninsular Plateau and the Central Highlands