The Shiva crater is a sea floor structure located beneath the Indian Ocean, west of Mumbai, India. It was named by the palaeontologist Sankar Chatterjee after Shiva, the Hindu god of destruction and renewal.
Its age is estimated to be around 65 million years, created at about the same time as a number of other impact craters and the Cretaceous-Tertiary extinction event (K-T boundary). Although the site has shifted since its formation because of sea floor spreading, the formation is approximately 600 kilometres (370 miles) long by 400 km (250 mi) wide. It is estimated that a crater of that size would have been made by an asteroid or comet approximately 40 km (25 mi) in diameter. The Shiva complex adds weight to the theory that the K-T extinction was caused by a massive asteroid fragmenting and hitting the Earth in several locations, known as the "multiple impact theory".[1]
At the time of the K-T extinction, India was located over the Réunion hotspot of the Indian Ocean. Hot material rising from the mantle flooded portions of India with a vast amount of lava, creating a plateau known as the Deccan Traps. It has been hypothesized that either the crater or the Deccan Traps associated with the area are the reason for the high level of oil and natural gas reserves in the region.[2]
There is some debate within the academic community over whether the "Shiva Crater" is indeed an impact crater.[3]
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Unlike many known crater formations, the Shiva complex is teardrop shaped, roughly 600 × 400 km (370 × 250 mi).[4] The complex itself is also unusually rectangular. Chatterjee hypothesizes that the low angle of an impact combined with boundary fault lines and unstable rock led to this unusual formation;[5] other researchers have noted that rock faults and impacts could modify the crater shape.[6] Similar to craters of its large size, the Shiva complex has concentric rings with a collapsed outer rim and a central spire- Shiva's is as high as Mount Everest.[4]
The age of the crater is inferred from the Deccan traps, which contain relatively high amounts of iridium (an element extremely rare in the Earth's crust but more common in asteroids). The crater also contains larger than average amounts of alkaline melt rocks, shocked quartz, and iron oxide laced with iridium;[7][8] these types of rocks and features suggest an impact origin.[4] In addition, the K-T boundary layer in India is one meter thick.[4] Assuming that the clay layer is the remains of scattered deposits from an asteroid impact, the thick layer would suggest that the actual impact occurred near India.
The discovery of Shiva and other features similar to impact craters like the Chicxulub site has led to the hypothesis that there were in fact multiple impacts which caused the massive extinction event at the end of the Cretaceous period.[9][10] Other theories have argued that since the Chicxulub impact is believed by some researchers to have occurred earlier than the extinction of the dinosaurs, Shiva's impact was enough to cause the mass extinction.[11][12]
While Chatterjee is confident that Shiva was one of many impacts, stating that "the K-T extinction was definitely a multiple-impact scenario,"[13] other scientists remain unconvinced that the extinction event was caused by multiple impacts, or that the Shiva feature is even in fact a crater. An article in the journal Nature suggested another supposed impact feature at Silverpit was in fact a sinkhole depression.[13]
| Cretaceous–Tertiary extinction event |
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| Proposed K–T boundary craters: Boltysh crater · Chicxulub crater · Shiva crater · Silverpit crater |
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