Movement of the Indian Plate
Plate Margins · 71-Ma Northward Drift from 50°S · Deccan Traps (60 Ma) & Himalayan Collision (40–50 Ma) (28 Micro-Realms)
The 71-Million-Year Odyssey of the Indian Plate (NCERT)
The Indian plate includes Peninsular India and the Australian continental portions. Once anchored at $50^\circ\text{S}$ latitude and separated from the Asian block by the Tethys Sea ($225\text{ Ma}$), India broke away from Gondwanaland, began its rapid northward journey about $200\text{ Ma}$ ($71\text{ Ma}$ to present track), poured out the Deccan Traps ($60\text{ Ma}$) over the Réunion hotspot, and collided with Eurasia $40\text{–}50\text{ Ma}$ to uplift the Himalayas—which are still rising today.
I. Tectonic Boundaries & Margins of the Indian Plate (NCERT)
Indo-Australian Dual Block
- Includes Peninsular India
- Plus Australian continent
- And intervening Indian Ocean
Northern Margin (Himalayas)
- Subduction zone along Himalayas
- Continent–Continent convergence
- Welds India to Eurasia
Eastern Margin (Rakinyoma)
→ JAVA
- Through Rakinyoma Mts (Myanmar)
- Via Andaman–Nicobar island arc
- Towards the Java Trench
SW Pacific Spreading Site
- Far eastern plate margin
- Spreading site east of Australia
- Oceanic ridge in SW Pacific
Western Margin (Kirthar)
- Follows Kirthar Mts of Pakistan
- Chaman fault & Sulaiman range
- Extends along Makran coast
Red Sea to Chagos Ridge
- Joins spreading site from Red Sea
- Southeastward along Carlsberg
- To Chagos Archipelago (NCERT)
Southern Boundary (Antarctic)
- Boundary with Antarctic Plate
- Marked by oceanic ridge
- Runs roughly W–E to New Zealand
II. Gondwana Breakup & The 71-Million-Year Northward Sprint
Tethys Sea (225 Ma)
- India was a large island
- Off the Australian coast
- Tethys Sea separated it from Asia
50° South Latitude Anchor
- Located as south as $50^\circ\text{S}$
- Deep in Southern Hemisphere
- Experienced Talchir glaciation
140-Ma Gondwana Break
- Northward journey ~200 Ma
- Broke from Antarctica/Aus ~140 Ma
- Opened proto-Indian Ocean
Madagascar Split (~88 Ma)
- Marion hotspot rifting (~88 Ma)
- Detached India from Madagascar
- Shaped straight West Coast
71 Ma to Present Track
- NCERT Fig 4.6 paleolatitudes
- 71 Ma $\to$ 55 Ma $\to$ 38 Ma $\to$ 10 Ma
- 6,000-km northward voyage
Record 15–20 cm/yr Sprint
- Fastest continental drift ever
- 15–20 cm/yr in Late Cretaceous
- Slowed to ~5 cm/yr after collision
Thin Lithospheric Keel
- Plume melted bottom of root
- Left thin ~100-km agile plate
- Pulled by double Tethyan slabs
III. Réunion Plume & Outpouring of the Deccan Traps (60 Ma — NCERT)
Crossing the Equator
- Crossed Equator ~55–50 Ma
- Shifted from temperate to tropical
- Triggered intense laterization
Réunion Mantle Plume
- Deep mantle hotspot blowtorch
- India passed directly over it
- Around 65 to 60 million yrs ago
Massive Fissure Eruptions
- Quiet, fluid basaltic lava floods
- Erupted through linear fissures
- During northward movement
Deccan Traps (60 Ma — NCERT)
- Started ~60 million yrs ago
- Continued for a long point of time
- Built 2,000-m thick step plateau
Chagos–Laccadive Trail
- Volcanic track left behind India
- Lakshadweep $\to$ Maldives $\to$ Chagos
- Ends at Réunion Island today
Western Ghats Escarpment
- Western flank faulted & subsided
- Submerged beneath Arabian Sea
- Tilted Peninsula eastward
Black Regur Soil Legacy
- Covers MH, MP, GJ, KA, TL
- Weathered into Black Cotton soil
- Gift of Réunion hotspot
IV. Eurasian Collision (40–50 Ma) & Continuing Rise of the Himalayas
Subduction of Tethys Floor
- Tethyan oceanic crust subducted
- Beneath southern Tibetan margin
- Formed Trans-Himalayan batholiths
Indus–Tsangpo Suture (ITSZ)
- Collision weld line
- Preserves Dras volcanic arc
- And squeezed Tethyan ophiolites
40–50 Ma Collision (NCERT)
40–50 MILLION YRS AGO
- Collided about 40–50 Myr ago
- Continent–Continent collision
- Caused rapid uplift of Himalayas
3-Phase Himalayan Uplift
- 1. Greater Himalayas (Eocene/Oligo)
- 2. Lesser Himalayas (Miocene)
- 3. Shiwalik foothills (Plio-Pleisto)
Syntaxial Hairpin Bends
- Aravalli & Assam craton prows
- Nanga Parbat (NW knee-bend)
- Namcha Barwa (NE knee-bend)
Indo-Gangetic Foredeep
- Downwarped crustal trough
- In front of rising Himalayas
- Filled by Indus-Ganga-Brahmaputra
Still Rising Today (NCERT)
- Subcontinent still moving north
- Height of Himalayas is rising
- Even to this date (NCERT)
Core Distinctions
• North: Subduction zone along the Himalayas (Continent–Continent convergence).
• East: Rakinyoma Mountains of Myanmar towards the island arc along the Java Trench; further east, a spreading site east of Australia in the SW Pacific.
• West: Kirthar Mountain of Pakistan $\to$ Makran coast $\to$ joins the spreading site from the Red Sea rift southeastward along the Chagos Archipelago.
• South: Divergent boundary with the Antarctic Plate (W–E oceanic ridge running south of New Zealand).
• 225 Ma: Tethys Sea separated India (at $50^\circ\text{S}$ latitude) from the Asian block.
• 200 Ma (140 Ma breakup): Started northward journey.
• 60 Ma: Outpouring of lava formed the Deccan Traps while still south of the Equator.
• 40–50 Ma: Collided with Asia, causing rapid uplift of the Himalayas.
World D Complete Matrix
Indian Plate Timeline (NCERT Chapter 4)