IIT Jodhpur
Seminar by Professor M. S. Sisodia (Geologist, PRL Ahmedabad)

Date and Venue Information
2 July  2019,  11 am, Seminar Room Electrical Engineering.
Title of the Seminar
"Meteorite impact craters: Identification and importance, some case histories from India" by Professor M. S. Sisodia (Geologist, PRL Ahmedabad)
Impact cratering is a fundamental process operating on all the celestial bodies of the Universe including the Earth. It is one of the primary mechanisms responsible for planetary accretion to shaping the planetary surfaces. Small and big extraterrestrial bodies have continuously hit the Earth since its formation, but the dynamic processes operating on the Earth have mostly obliterated the impact signatures. The Earth Impact Database shows details of only about 180 known impact structures. Only three impact craters have been identified in India, viz., Lonar in Maharashtra, Dhala in M.P. and Ramgarh in Rajasthan. Some more craters are suspected to have formed due to impact but are still to be confirmed.  
The potential of impacts resulting into formation of economic mineral deposits is noteworthy. The gold and uranium deposits at Vredefort (S. Africa), iron ore deposit at Ternovka (Ukraine), uranium deposit at Carswell (Canada), nickel and platinum group elements deposits at Sudbury (Canada), and diamonds at Kara (Russia) have formed due to large impacts. Similarly, Ames, Red Wing Creek, Newporte, Avak (USA); Campeche (Mexico); Boltysh (Ukraine); Bosumtwi (Ghana) are impact craters that are being exploited for hydrocarbons.  
Shock-metamorphosed features, such as shatter cones, impact breccia, planar deformation features (PDF) and the minerals like stishovite, maskelinite, ringwoodite etc. that are produced at about 10 to 20 GPA can unambiguously confirm impact craters on the Earth. Geochemical anomalies such as higher concentration of platinum group elements, noble gases or isotopic anomalies are also confirmatory evidences for impact craters.  
The process of impacting if fully understood can possibly resolve many unanswered questions in earth sciences, for instance: it has been propounded that phosphorus on the Earth that led to evolution of higher species was possibly brought by an impact during the Proterozoic. The Jaisalmer Basin in Rajasthan after years of exploration activity has yielded only gas but no oil. The reason inferred for this is incomplete maturity of the sediments. On the contrary, the Barmer Basin though juxtaposed with the Jaisalmer Basin is yielding oil, possibly because of an impact, which produced heat impulse to create completely euxinic conditions for generation of oil from the pre-existing biomass. Malani (rhyolite) beds have been inferred to have originated due to volcanism but show many features that are unusual for any volcanic formation. It is important to note that stishovite has been reported from Malani Rhyolite, which is an unambiguous evidence for impact.