Global Plate Tectonics and India Subcontinent

1. Global Plate Tectonics

The theory of Plate Tectonics explains how the Earth's lithosphere (the rigid outer shell) is broken into large pieces called plates.

Plates: These plates float over the softer, semi-molten layer beneath, called the asthenosphere.
Movement: Driven by heat from Earth's interior (mantle convection, ridge push, slab pull), plates move a few centimetres per year — about the speed your fingernails grow.
Boundaries: Where plates meet, we get different interactions:
1. Divergent boundaries – plates move apart (mid-ocean ridges, new crust formation).
2. Convergent boundaries – plates collide (mountains, subduction zones).
3. Transform boundaries – plates slide past each other (earthquakes).

Why it matters: This movement shapes continents, mountains, volcanoes, ocean basins, and earthquakes.

2. India's Place in Global Plate Tectonics

India's geologic story is one of the most dramatic and fast-moving continental journeys in Earth's history.

Past position: Around 150 million years ago (Mesozoic Era), India was part of the southern supercontinent Gondwanaland, along with Africa, Antarctica, Australia, and South America.
Breakup: About 120 million years ago, the Indian plate broke away and started moving northwards across the Tethys Ocean.
Fast motion: India moved unusually quickly — about 15–20 cm/year at times (triple the average speed of plates).
Collision: Around 50 million years ago, the Indian plate collided with the Eurasian plate.
Result: The Himalayas and the Tibetan Plateau began to rise — and they are still rising today.

3. Current Tectonic Setting of India

Plate boundaries around India:
- North: Convergent boundary with the Eurasian Plate → Himalayan orogeny (mountain building) and seismic activity in the Himalayan belt.
- West: Transform and convergent interactions with the Arabian Plate along the Owen Fracture Zone and Makran Subduction Zone (earthquake risks in Gujarat, Arabian Sea).
- East: Convergent boundary with the Burma Plate and Sunda Plate → Andaman–Nicobar volcanic arc and earthquakes.
- South: Surrounded by the Indian Ocean spreading ridges (divergent boundaries) in the southwest and southeast.
Seismic zones: India has four main seismic zones (II–V), with Zone V being the most active (NE India, Kashmir, Andaman–Nicobar).

4. Key Effects on India

Himalayan growth: Still rising ~5 mm/year; ongoing earthquakes.
Peninsular stability: Generally stable, but intraplate quakes occur (e.g., Latur, Koyna) due to ancient fault reactivation.
Volcanism: Andaman–Nicobar volcanic activity (Barren Island volcano).
Tsunamis: Risk from undersea earthquakes (2004 Indian Ocean tsunami).

Time Period	Event	Impact
~150 Ma	India part of Gondwanaland	Connected to Antarctica, Africa, Australia
~120 Ma	Broke away from Gondwanaland	Started moving north
~50 Ma	Collision with Eurasia	Formation of Himalayas, Tibetan Plateau
Present	Active convergence & seismicity	Earthquakes, mountain building, volcanism

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