Indian Plate

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  The Indian plate shown in red

The India Plate or Indian Plate is a tectonic plate that was originally a part of the ancient continent of Gondwana from which it split off, eventually becoming a major plate. About 55 to 50 million years ago it fused with the adjacent Australian Plate. It is today part of the major Indo-Australian Plate, and includes most of South Asia – i.e., the Indian subcontinent – and a portion of the basin under the Indian Ocean, including parts of South China and Eastern Indonesia,[1][2][3] and extending up to but not including Ladakh, Kohistan and Balochistan.[4][5][6]

Plate movements

Due to plate tectonics, the India Plate split from Madagascar and collided (c. 55 Ma) with the Eurasian Plate, resulting in the formation of the Himalayas.

140 million years ago the Indian Plate formed part of the supercontinent Gondwana together with modern Africa, Australia, Antarctica, and South America. Gondwana broke up as these continents drifted apart with different velocities,[7] a process which led to the opening of the Indian Ocean.[8]

In the late Cretaceous about 90 million years ago, subsequent to the splitting off from Gondwana of conjoined Madagascar and India, the Indian Plate split from Madagascar. It began moving north, at about 20 centimetres (7.9 in) per year,[7] and is believed to have begun colliding with Asia between 55 and 50 million years ago,[9] in the Eocene epoch of the Cenozoic, although this is contested, with some authors suggesting it was much later at around 35 million years ago.[10] If the collision occurred between 55 and 50 Ma, the Indian Plate would have covered a distance of 3,000 to 2,000 kilometres (1,900 to 1,200 mi), moving faster 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 (~1300 km) and the amount of convergence between India and Asia (~3600 km).[11] 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 Ma. This was followed by the "hard collision" between India and Asia occurred at ~25 Ma. 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.

In 2007, German geologists[7] suggested that the reason the Indian Plate moved so quickly is that it is only half as thick (100 kilometres or 62 miles) as the other plates[12] which formerly constituted Gondwana. The mantle plume that once broke up Gondwana might also have melted the lower part of the Indian subcontinent, which allowed it to move both faster and further than the other parts.[7] The remains of this plume today form the Marion, Kerguelen, and Réunion hotspots.[8] As India moved north, it is possible that the thickness of the Indian plate degenerated further as it passed over the hotspots and magmatic extrusions associated with the Deccan and Rajmahal Traps.[8] The massive amounts of volcanic gases released during the passage of the Indian Plate over the hotspots have been theorised to have played a role in the Cretaceous–Paleogene extinction event, generally held to be due to a large asteroid impact.[13]

The collision with the Eurasian Plate along the boundary between India and Nepal formed the orogenic belt that created the Tibetan Plateau and the Himalaya Mountains, as sediment bunched up like earth before a plow.

The Indian Plate is currently moving north-east at 5 centimetres (2.0 in) per year, while the Eurasian Plate is moving north at only 2 centimetres (0.79 in) per year. This is causing the Eurasian Plate to deform, and the India Plate to compress at a rate of 4 millimetres (0.16 in) per year.

Recent events

Closeup of the boundary with the Eurasian, African and Arabian plates; the 2005 Kashmir earthquake occurred at the northern tip of the Indian plate.

2004 Indian Ocean earthquake

The 9.1-9.3 moment magnitude 2004 Indian Ocean earthquake was caused by the release of stresses built up along the subduction zone where the Indian Plate is sliding under the Burma Plate in the eastern Indian Ocean, at a rate of 6 cm/yr (2.5 in/yr). The Sunda Trench is formed along this boundary where the Indo-Australian and Eurasian Plates meet. Earthquakes in the region are either caused by thrust faulting, where the fault slips at right angles to the trench; or strike-slip faulting, where material to the east of the fault slips along the direction of the trench.

Like all similarly large earthquakes, the December 26, 2004 event was caused by thrust-faulting. A 100 kilometres (62 mi) rupture caused about 1,600 kilometres (990 mi) of the interface to slip, which moved the fault 15 metres (49 ft) and lifted the sea floor several metres (yards), creating the great tsunami.[14]

2005 Kashmir earthquake

Main article: 2005 Kashmir earthquake

On 8 October 2005, an earthquake of magnitude 7.6 occurred near Muzaffarabad, Kashmir, Pakistan killing more than 80,000 people, and leaving more than 2.5 million homeless.

See also

Notes

  1. ↑ Sinvhal, Understanding Earthquake Disasters, page 52, Tata McGraw-Hill Education, 2010, ISBN 978-0-07-014456-9
  2. ↑ Harsh K. Gupta, Disaster management, page 85, Universities Press, 2003, ISBN 978-81-7371-456-6
  3. ↑ James R. Heirtzler, Indian ocean geology and biostratigraphy, page American Geophysical Union, 1977, ISBN 978-0-87590-208-1
  4. ↑ M. Asif Khan, Tectonics of the Nanga Parbat syntaxis and the Western Himalaya, page 375, Geological Society of London, 2000, ISBN 978-1-86239-061-4
  5. ↑ Srikrishna Prapnnachari, Concepts in Frame Design, page 152, Srikrishna Prapnnachari, ISBN 978-99929-52-21-4
  6. ↑ A. M. Celâl Şengör, Tectonic evolution of the Tethyan Region, Springer, 1989, ISBN 978-0-7923-0067-0
  7. ↑ 7.0 7.1 7.2 7.3 Kind 2007
  8. ↑ 8.0 8.1 8.2 Kumar et al. 2007
  9. ↑ Scotese 2001
  10. ↑ Aitchison, Ali & Davis 2007
  11. ↑ van Hinsbergen, D.; Lippert, P.; Dupont-Nivet, G.; McQuarrie, N.; Doubrivine, P.; Spakman, W.; Torsvik, T. (2012). "Greater India Basin hypothesis and a two-stage Cenozoic collision between India and Asia". Proceedings of the National Academy of Sciences 109 (20): 7659–7664. Bibcode:2012PNAS..109.7659V. doi:10.1073/pnas.1117262109. 
  12. ↑ The lithospheric roots in South Africa, Australia, and Antarctica are 300 to 180 kilometres (190 to 110 mi) thick. (Kumar et al. 2007) See also Kumar et al. 2007, figure 1,
  13. ↑ Schulte, Peter; et al. (5 March 2010). "The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary". Science (AAAS) 327 (5970): 1214–1218. Bibcode:2010Sci...327.1214S. doi:10.1126/science.1177265. ISSN 1095-9203. PMID 20203042. Retrieved 5 March 2010. 
  14. ↑ Chen 2005

References

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Coordinates: 34°25′55″N 73°32′13″E / 34.43194°N 73.53694°E / 34.43194; 73.53694

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