| 词条 | Shiva crater |
| 释义 |
| name = Shiva crater | other_name = | photo = | photo_size = | photo_alt = | photo_caption = | map = India | map_alt = | map_caption = Location of the crater offshore India | map_size = | location = Mumbai Offshore Basin | label = | label_position = | coordinates = {{coord|18|40|N|70|14|E|type:landmark_region:IN_scale:10000000|display=inline,title}} | coordinates_ref = | confidence = | diameter = {{convert|500|km|mi|abbr=on}} | depth = | rise = | imp_size = | age = ~66 Cretaceous–Paleogene boundary | exposed = No | drilled = No | bolide = | translation = | language = | pronunciation = | topo = | access = | country = {{IND}} | state = | province = | district = | municipality = }} The Shiva Crater is a geologic structure, which is hypothesized by Sankar Chatterjee[1] and colleagues to be a {{convert|500|km|mi|adj=on}} diameter impact structure. This geologic structure consists of the Bombay High and Surat Depression. They lie beneath the Indian continental shelf and the Arabian Sea west of Mumbai, India. Chatterjee named this structure after Shiva, the Hindu god of destruction and renewal.[1][2] ArgumentsChatterjee argues that the Shiva Crater was formed around 65 million years ago, about the same time as a number of other impact craters and the Cretaceous–Paleogene extinction event (Cretaceous–Paleogene boundary / K-Pg boundary). Although the site has shifted since its formation because of sea floor spreading, the formation is approximately {{convert|600|km|abbr=off}} long by {{convert|400|km|abbr=on}} wide. It is estimated that this proposed crater would have been made by an asteroid or comet approximately {{convert|40|km|abbr=on}} in diameter.[1][2] At the time of the Cretaceous–Paleogene 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.[3] Earth scientists in general remain unconvinced that the "Shiva Crater" is indeed an impact crater. For example, Christian Koeberl, a professor of impact research and planetary geology at the University of Vienna, Austria, regards the Shiva Crater to be "a figment of imagination."[4][5] Currently, it is not recognized as an impact crater by the Earth Impact Database of the Planetary and Space Science Centre at the University of New Brunswick, Canada. Geology and morphologyUnlike typical known extraterrestrial impact structures, Shiva is teardrop shaped, roughly {{convert|600|x|400|km|abbr=on}}. 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.[2] The age of the structure is inferred from the Deccan Traps which overlie part of it.[2] Shiva and mass extinction{{main|Cretaceous–Paleogene extinction event}}The proposed Shiva Crater and other possible impact craters along with the Chicxulub 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."[6] 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 by itself.[7][8] However, other scientists remain unconvinced that the extinction event was caused by multiple impacts, or that the Shiva feature is even in fact a crater.[4] Evidence published in a 2013 Science article by Paul 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.[9] See also
References1. ^1 2 {{cite book|last=Chatterjee|first=S.|title=Comparative Planetology, Geological Education, History of Geology: Proceedings of the 30th International Geological Congress, Beijing, China, 4–14 August 1996|chapter-url=https://books.google.com/books?id=3IORF1Ei3LIC&pg=PA31|year=1997|publisher=VSP|isbn=978-90-6764-254-5|pages=31–54|chapter='Multiple impacts at the KT boundary and the death of the dinosaurs}} 2. ^1 2 3 Chatterjee, S., N. Guven, A. Yoshinobu, and R. Donofrio. (2006) Shiva Structure: a possible KT boundary impact crater on the western shelf of India. Museum of Texas Tech University Special Publications. 50, 39pp. 3. ^{{cite journal |author=Agrawal, P., Pandey, O. |date=November 2000 |title= Thermal regime, hydrocarbon maturation and geodynamic events along the western margin of India since late Cretaceous|journal= Journal of Geodynamics|volume= 30|issue=4 |pages=439–459 |id= |laysummary= https://www.sciencedirect.com/science/article/pii/S0264370700000028|doi= 10.1016/S0264-3707(00)00002-8 |bibcode = 2000JGeo...30..439P }} 4. ^1 {{cite web|author=Mullen, Leslie|date=2004-11-02|url=http://www.spacedaily.com/news/deepimpact-04r.html|title=Shiva: Another K-T Impact?|work=SpaceDaily|accessdate=2008-02-20}} - original article at source 5. ^{{Cite web |url=http://www.space.com/scienceastronomy/091018-dinosaur-crater.html |title=New Dino-destroying Theory Fuels Hot Debate |first=Clara |last=Moskowitz |publisher=space.com |date=18 October 2009 }} 6. ^Rampino, M. R., and B. M. Haggerty (1996) The “Shiva Hypothesis”: Impacts, mass extinctions, and the galaxy. Earth, Moon, and Planets. 72(1–3):441–460. 7. ^Davis, J. W. (2006) [https://web.archive.org/web/20070505021703/http://www.depts.ttu.edu/communications/news/stories/06-11-dinosaur.php archived copy of http://www.depts.ttu.edu/communications/news/stories/06-11-dinosaur.php Texas Tech Paleontologist Finds Evidence That Meteorite Strike Near Bombay May Have Wiped Out Dinosaurs.] Texas Tech Today, Texas Tech University, Lubbock, Texas. 8. ^Dinosaur theory now extinct?; Asteroid didn't destroy species, researchers find Mexican crater older than first believed; [ONT Edition] Toronto Star. Toronto, Ont.: Mar 2, 2004. pg. A.02 9. ^{{cite journal|last1=Renne|first1=Paul|url=https://eps.harvard.edu/files/eps/files/renne.kt_.science.2013.pdf|title=Time Scales of Critical Events Around the Cretaceous-Paleogene Boundary|journal=Science|date=8 February 2013|volume=339|issue=6120|pages=684–7|bibcode=2013Sci...339..684R|doi=10.1126/science.1230492|pmid=23393261}} External links
4 : Impact craters of India|Possible impact craters on Earth|Cretaceous impact craters|Geology of the Indian Ocean |
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