India can be broadly divided into two major physiographic and geological provinces: the Peninsular India and the Extra-Peninsular India (Himalayan region). These two regions exhibit stark differences in their geomorphological (landforms) and geological (rock types, structures, and history) characteristics, reflecting their distinct tectonic histories.

1. Peninsular India:

• Geological Features:

  • Ancient Crystalline Rocks: Comprises some of the oldest and most stable landmasses on Earth, primarily composed of Precambrian crystalline rocks (gneisses, granites, schists) that are part of the Gondwana supercontinent.
  • Stable Block: Geologically a stable block, often referred to as a 'shield' or 'craton', which has largely remained undisturbed by major tectonic activity since the Precambrian.
  • Sedimentary Cover: Limited sedimentary cover, mainly Cuddapah and Vindhyan Supergroups (Proterozoic), and Gondwana sediments (Permo-Carboniferous to Jurassic) in rift basins (e.g., Damodar Valley).
  • Deccan Traps: A significant portion of the northwestern peninsula is covered by extensive flood basalts known as the Deccan Traps, formed during the Late Cretaceous-Early Paleocene.
  • Mineral Rich: Rich in metallic minerals (iron ore, manganese, bauxite) and non-metallic minerals (mica, limestone) due to its ancient crystalline nature.

• Geomorphological Features:

  • Plateau Landscape: Dominated by a vast plateau, gently sloping eastward, with an average elevation of 600-900 meters.
  • Erosional Features: Characterized by mature river systems (e.g., Godavari, Krishna, Kaveri, Mahanadi) with broad valleys and deltas, indicating long periods of erosion and stability.
  • Residual Mountains: Features like the Aravallis, Vindhyas, Satpuras, Western Ghats, and Eastern Ghats are mostly relict or residual mountains, formed by erosion of ancient uplifted blocks, rather than recent tectonic folding.
  • Coastal Plains: Narrow coastal plains along the Arabian Sea and broader plains along the Bay of Bengal.
  • Absence of Glacial Features: Generally lacks extensive glacial features, except for some high-altitude areas in the Western Ghats.

2. Extra-Peninsular India (Himalayan Region):

• Geological Features:

  • Young Fold Mountains: Represents a young, tectonically active mountain belt formed by the ongoing collision of the Indian Plate with the Eurasian Plate, starting about 50 million years ago.
  • Sedimentary and Metamorphic Rocks: Composed primarily of marine sedimentary rocks (limestones, shales, sandstones) and metamorphic rocks (slates, phyllites, schists, gneisses) that were uplifted and intensely folded, faulted, and thrusted.
  • Complex Structure: Characterized by complex geological structures including nappe folds, thrust faults (e.g., Main Central Thrust, Main Boundary Thrust), and imbricate structures.
  • Igneous Intrusions: Presence of granitic intrusions (e.g., Ladakh Batholith) and ophiolites (remnants of oceanic crust) indicating past oceanic environments and subduction.
  • Seismically Active: Highly seismically active due to ongoing plate convergence, making it one of the most earthquake-prone regions globally.

• Geomorphological Features:

  • Rugged Topography: Characterized by extremely rugged, high-relief topography with towering peaks (e.g., Mount Everest), deep gorges, and steep slopes.
  • Youthful River Systems: Rivers (e.g., Indus, Ganga, Brahmaputra) are antecedent, meaning they predate the uplift of the Himalayas and have cut deep, V-shaped valleys and spectacular canyons.
  • Glacial Features: Extensive glacial features, including glaciers, cirques, moraines, and glacial lakes, especially in the higher reaches.
  • Active Erosion and Deposition: High rates of erosion due to steep slopes and active tectonics, leading to significant sediment transport and deposition in the Indo-Gangetic plains.
  • Landslides and Mass Wasting: Prone to frequent landslides, rockfalls, and other mass wasting events due to unstable slopes and seismic activity.

In summary, Peninsular India is an ancient, stable, eroded plateau with relict mountains and mature river systems, while Extra-Peninsular India is a young, tectonically active, high-relief mountain belt with complex structures, youthful rivers, and extensive glacial features, reflecting their contrasting origins and evolutionary paths.