| Shiva crater | |
|---|---|
  Location of the proposed crater offshore India | |
| Impact crater/structure | |
| Confidence | Dubious |
| Diameter | 500 km (310 mi) |
| Age | Claimed to be ~66 million years[1] Cretaceous–Paleogene boundary |
| Exposed | No |
| Drilled | No |
| Location | |
| Location | Mumbai Offshore Basin |
| Coordinates | 18°40′N70°14′E / 18.667°N 70.233°E /18.667; 70.233 |
| Country | India |
TheShiva crater is the claim bypaleontologistSankar Chatterjee[2] and colleagues that theBombay High andSurat Depression on the Indian continental shelf west ofMumbai,India represent a 500-kilometre-wide (310 mi) impact crater, that formed around theCretaceous-Paleogene boundary. Chatterjee and colleagues have claimed that this could have contributed to theK-Pg extinction event. Other scholars have questioned the claims, finding that there is no evidence of an impact structure.
Chatterjee argues that the Shiva crater was formed around 65 million years ago, about the same time as a number of other impact craters and theCretaceous–Paleogene extinction event (Cretaceous–Paleogene boundary / K-Pg boundary). Although the site has shifted since its formation because ofsea floor spreading, the formation is approximately 600 kilometres (370 miles) long by 400 km (250 mi) wide. If its status as an impact crater is ever confirmed, the Shiva crater would be the largest known impact crater on Earth. It is estimated that this proposed crater would have been made by anasteroid orcomet approximately 40 km (25 mi) in diameter.[2][3]
At the time of the Cretaceous–Paleogene extinction, India was located over theRéunion hotspot of the Indian Ocean. Hot material rising from themantle flooded portions of India with a vast amount oflava, creating a plateau known as theDeccan Traps. It has been hypothesized that either the crater or the Deccan Traps associated with the area is the reason for the high level of oil and natural gas reserves in the region.[4]
Unlike typical known extraterrestrial impact structures, Shiva is teardrop shaped, roughly 600 km × 400 km (370 mi × 250 mi). It is also unusually rectangular. Chatterjee argues that the low angle of an impact combined with boundary fault lines and unstable rock led to this unusual formation.[3] The age of the structure is inferred from theDeccan Traps which overlie part of it.[3]
The proposed Shiva crater and other possible impact craters along with theChicxulub crater have led to the hypothesis that multiple impacts caused the massive extinction event at the end of the Cretaceous period. Chatterjee is confident that Shiva was one of many impacts, stating that "the K-T extinction was definitely a multiple-impact scenario."[5] Other theories have argued that since the Chicxulub impact is believed by some researchers to have occurredearlier than the extinction of the non-avian dinosaurs, Shiva's impact was enough to cause the mass extinction by itself.[6] An article published inScience 2013 byPaul R. Renne at the University of California at Berkeley suggests that the Chicxulub crater is in fact within the time frame of when the mass extinction occurred.[7]
The claims of an impact crater have been criticised.Christian Koeberl, a Professor of Geology at theUniversity of Vienna and a specialist on impact craters, described the claims in 2004 as "a figment of imagination", stating that the claims were "inconsistent not only with the regional geology and geophysics, but also with anything we know about impact cratering."[8] American geologistGerta Keller stated in 2007, "We have worked extensively throughout India and investigated a number of the localities where Sankar Chatterjee claims to have evidence of a large impact he calls Shiva crater... Unfortunately, we have found no evidence to support his claims. Sorry to say, this is all nonsense." Geophysicist Sean Gulick stated in the same year, "There's a bunch of problems to say the least. There is no evidence that [Chatterjee is] presenting of it actually being a crater", and described the oval shape of the structure as unlikely for an impact crater.[9] In the chapter "Impact Cratering from an Indian Perspective", from the 2013 bookEarth System Processes and Disaster Management, geologists Jayanta K. Pati and Puniti Pati write that "...the proposed Shiva structure in the Arabian Sea to the southwest of the Indian subcontinent (Chatterjee et al. 2006) have also been suggested to be of possible impact origin. However, Chatterjee et al. (2006) do not provide any substantial evidence for the existence of a crater structure and certainly not for the existence of an impact structure at Shiva."[10]
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