Deccan Traps
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The Deccan Traps is a large igneous province located on the Deccan Plateau of west-central India and is one of the largest volcanic features on Earth. It consists of multiple layers of solidified flood basalt that together are more than 2,000 m thick and cover an area of 500,000 km². The term 'traps' is derived from the Swedish word for stairs (trappa, or sometimes trapp), referring to the step-like hills forming the landscape of the region.
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[edit] History
The Deccan Traps formed between 60 and 68 million years ago,[1][2] at the end of the Cretaceous period. The bulk of the volcanic eruption occurred at the Western Ghats (near Mumbai) some 66 million years ago. This series of eruptions may have lasted fewer than 30,000 years in total. The gases released in the process may have played a role in the K-T extinction event, which included the extinction of the dinosaurs.
Before the Deccan Traps region was reduced to its current size by erosion and continental drift, it is estimated that the original area covered by the lava flows was as large as 1.5 million km², approximately half the size of modern India. The present volume of directly observable lava flows is estimated to be around 512,000 km³.
[edit] Chemical composition
Within the Deccan Traps at least 95% of the lavas are tholeiitic basalts, however other rock types occur:
Mantle xenoliths have been described from Kutch (northwestern India) and elsewhere in the western Deccan.
[edit] Theories of formation
It is postulated that the Deccan Traps eruption was associated with a deep mantle plume. The area of long-term eruption (the hotspot), known as the Réunion hotspot, is suspected of both causing the Deccan Traps eruption and opening the rift that once separated the Seychelles plateau from India. Seafloor spreading at the boundary between the Indian and African Plates subsequently pushed India north over the plume, which now lies under Réunion island in the Indian Ocean, southwest of India. The mantle plume model has, however, been challenged.[1]
[edit] Link to Shiva Crater
A large impact crater has been recently reported in the sea floor off the west coast of India. Called the Shiva crater, it has also been dated at sixty-five million years, right at the Cretaceous-Tertiary (K/T) boundary. The researchers suggest that the impact may have been the triggering event for the Deccan Traps as well as contributing to the acceleration of the Indian plate in the early Tertiary.[3] However, opinion in the geologic community is not unanimous that this feature is actually an impact crater.[4] Also, the reported age is in the middle of the ages given for the Deccan rocks.
[edit] Analogues to Venus flood eruptions
The planet Venus is also thought to undergo vast basaltic flood eruptions, but on an even greater scale than those at Deccan Traps. It is not known whether the mechanisms are similar; Venus appears to lack Earth's plate tectonics and its internal structure may differ in other ways as well.
