| Indian plate | |
|---|---|
 | |
| Type | Minor |
| Approximate area | 11,900,000 km2 (4,600,000 sq mi)[1] |
| Movement1 | North-east |
| Speed1 | 26–36 mm/a (1.0–1.4 in/year)[citation needed] |
| Features | Indian subcontinent,Indian Ocean,Arabian Sea,Himalayas |
| 1Relative to theAfrican plate | |
TheIndian plate (orIndia plate) is aminor tectonic plate straddling theequator in theEastern Hemisphere. Originally a part of the ancient continent ofGondwana, the Indian plate broke away from the other fragments of Gondwana100 million years ago and began moving north, carryingInsular India with it.[2] It was once fused with the adjacentAustralian plate to form a singleIndo-Australian plate, but recent studies suggest that India and Australia may have been separate plates for at least 3 million years.[3] The Indian plate includes most of modernSouth Asia (theIndian subcontinent) and a portion of the basin under theIndian Ocean, includingparts of South China,Indonesian islands,[4][5] and extending up to but not includingLadakh,Kohistan, andBalochistan in Pakistan.[6][7][8]
Until roughly140 million years ago, the Indian plate formed part of thesupercontinent,Gondwana, together with modern Africa, Australia, Antarctica, and South America. Gondwana fragmented as these continents drifted apart at different velocities;[9] a process which led to the opening of theIndian Ocean.[10]
In the lateCretaceous approximately100 million years ago, and subsequent to the splitting fromGondwana of conjoinedMadagascar andIndia, the Indian plate split from Madagascar and formedInsular India. It began moving north, at about 20 cm (7.9 in) per year,[9] and is believed to have begun colliding with Asia as early as55 million years ago,[11] in theEocene epoch of theCenozoic. However, some authors suggest the collision between India and Eurasia occurred much later, around35 million years ago.[12] If the collision occurred between 55 and 50 Mya, the Indian plate would have covered a distance of 3,000 to 2,000 km (1,900–1,200 mi), moving more quickly than any other known plate. In 2012,paleomagnetic data from the Greater Himalaya was used to propose two collisions to reconcile the discrepancy between the amount of crustal shortening in the Himalaya (~1,300 km or 800 mi) and the amount of convergence between India and Asia (~3,600 km or 2,200 mi).[13] These authors propose a continental fragment of northern Gondwana rifted from India, traveled northward, and initiated the "soft collision" between the Greater Himalaya and Asia at ~50 Mya. This was followed by the "hard collision" between India and Asia occurred at ~25 Mya.Subduction of the resulting ocean basin that formed between the Greater Himalayan fragment and India explains the apparent discrepancy between the crustal shortening estimates in the Himalaya and paleomagnetic data from India and Asia. However, the proposed ocean basin was not constrained by paleomagnetic data from the key time interval of ~120 Mya to ~60 Mya. New paleomagnetic results of this critical time interval from southern Tibet do not support this Greater Indian Ocean basin hypothesis and the associated dual collision model.[14]
In 2007, German geologists[9] suggested the reason the Indian plate moved so quickly is that it is only half as thick (100 km or 62 mi) as the other plates[15] which formerly constituted Gondwana. Themantle plume that once broke up Gondwana might also have melted the lower part of theIndian subcontinent, which allowed it to move both more quickly and farther than the other parts.[9] The remains of this plume today form theMarion hotspot (Prince Edward Islands), theKerguelen hotspot, and theRéunion hotspots.[10][16] As India moved north, it is possible the thickness of the Indian plate degenerated further as it passed over the hotspots and magmatic extrusions associated with theDeccan andRajmahal Traps.[10] The massive amounts ofvolcanic gases released during the passage of the Indian plate over the hotspots have been theorised to have played a role in theCretaceous–Paleogene extinction event, generally held to be due to alarge asteroid impact.[17]
In 2020, however, geologists at theUniversity of Oxford and theAlfred Wegener Institute found that new plate-motion models displayed increased movement speeds in allmid-ocean ridges during the late Cretaceous, a result irreconcilable to current theories of plate tectonics and a refutation of the plume-push hypothesis. Pérez-Díaz concludes that the accelerated movement of the Indian plate is an illusion wrought by large errors ingeomagnetic reversal timing around theCretaceous–Paleogene boundary, and that a recalibration of the time scale shows no such acceleration exists.[18][19]
The collision with theEurasian plate along the boundary between India andNepal formed theorogenic belt that created theTibetan Plateau and theHimalaya Mountains, as sediment bunched up like earth before aplow.
The Indian plate is currently moving north-east at five cm (2.0 in) per year, while the Eurasian plate is moving north at only two cm (0.79 in) per year. This is causing the Eurasian plate to deform, and the Indian plate to compress at a rate of four mm (0.16 in) per year.[citation needed]
The westerly side of the Indian plate is a transform boundary with theArabian plate called theOwen fracture zone, and adivergent boundary with theAfrican plate called theCentral Indian Ridge (CIR). The northerly side of the plate is aconvergent boundary with theEurasian plate forming theHimalaya andHindu Kushmountains, called theMain Himalayan Thrust.[citation needed]
Media related toIndian tectonic plate at Wikimedia Commons
