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The Deccan Traps is a large igneous province of west-central India. It is one of the largest volcanic features on Earth, taking the form of a large shield volcano. It consists of numerous layers of solidified flood basalt that together are more than about 2,000 metres (6,600 ft) thick, cover an area of about 500,000 square kilometres (200,000 sq mi), and have a volume of about 1,000,000 cubic kilometres (200,000 cu mi). Originally, the Deccan Traps may have covered about 1,500,000 square kilometres (600,000 sq mi), with a correspondingly larger original volume. This volume overlies the Archean age Indian Shield, which is likely the lithology the province passed through during eruption. The province is commonly divided into four subprovinces: the main Deccan, the Malwa Plateau, the Mandla Lobe, and the Saurashtran Plateau.
An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effect. When large objects impact terrestrial planets such as the Earth, there can be significant physical and biospheric consequences, though atmospheres mitigate many surface impacts through atmospheric entry. Impact craters and structures are dominant landforms on many of the Solar System's solid objects and present the strongest empirical evidence for their frequency and scale.
The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is offshore near the community of Chicxulub, after which it is named. It was formed slightly over 66 million years ago when a large asteroid, about ten kilometers in diameter, struck Earth. The crater is estimated to be 180 kilometers in diameter and 20 kilometers in depth. It is the second largest confirmed impact structure on Earth, and the only one whose peak ring is intact and directly accessible for scientific research.
An impact winter is a hypothesized period of prolonged cold weather due to the impact of a large asteroid or comet on the Earth's surface. If an asteroid were to strike land or a shallow body of water, it would eject an enormous amount of dust, ash, and other material into the atmosphere, blocking the radiation from the Sun. This would cause the global temperature to decrease drastically. If an asteroid or comet with the diameter of about 5 km (3.1 mi) or more were to hit in a large deep body of water or explode before hitting the surface, there would still be an enormous amount of debris ejected into the atmosphere. It has been proposed that an impact winter could lead to mass extinction, wiping out many of the world's existing species. The Cretaceous–Paleogene extinction event probably involved an impact winter, and led to mass extinction of most tetrapods weighing more than 25 kilograms.
Walter Alvarez is a professor in the Earth and Planetary Science department at the University of California, Berkeley. He is most widely known for the theory that dinosaurs were killed by an asteroid impact, developed in collaboration with his father, Nobel Prize–winning physicist Luis Alvarez.
Chicxulub Pueblo is a town, and surrounding municipality of the same name, in the Mexican state of Yucatán.
The year 1991 in science and technology involved many significant events, some listed below.
The Boltysh crater or Bovtyshka crater is a buried impact crater in the Kirovohrad Oblast of Ukraine, near the village of Bovtyshka. The crater is 24 kilometres (15 mi) in diameter and its age of 65.39 ± 0.14/0.16 million years, based on argon-argon dating techniques, less than 1 million years younger than Chicxulub crater in Mexico and the Cretaceous–Paleogene boundary. The Chicxulub impact is believed to have caused the mass extinction at the end of the Cretaceous period, which included the extinction of the non-avian dinosaurs. The Boltysh crater is currently thought to be unrelated to the Chicxulub impact, and to have not generated major global environmental effects.
The Yucatán Peninsula is a large peninsula in southeast Mexico and adjacent portions of Belize and Guatemala. The peninsula extends towards the northeast, separating the Gulf of Mexico to the north and west of the peninsula from the Caribbean Sea to the east. The Yucatán Channel, between the northeastern corner of the peninsula and Cuba, connects the two bodies of water.
The Shiva crater is the claim by paleontologist Sankar Chatterjee and colleagues that the Bombay High and Surat Depression on the Indian continental shelf west of Mumbai, India represent a 500-kilometre (310 mi) impact crater, that formed around the Cretaceous-Paleogene boundary. Chatterjee and colleagues have claimed that this could have contributed to the K-Pg extinction event. Other scholars have questioned the claims, finding that there is no evidence of an impact structure.
The Alvarez hypothesis posits that the mass extinction of the non-avian dinosaurs and many other living things during the Cretaceous–Paleogene extinction event was caused by the impact of a large asteroid on the Earth. Prior to 2013, it was commonly cited as having happened about 65 million years ago, but Renne and colleagues (2013) gave an updated value of 66 million years. Evidence indicates that the asteroid fell in the Yucatán Peninsula, at Chicxulub, Mexico. The hypothesis is named after the father-and-son team of scientists Luis and Walter Alvarez, who first suggested it in 1980. Shortly afterwards, and independently, the same was suggested by Dutch paleontologist Jan Smit.
Gerta Keller is a geologist and paleontologist who contests the Alvarez hypothesis that the impact of the Chicxulub impactor, or another large celestial body, directly caused the Cretaceous–Paleogene extinction event. Keller maintains that such an impact predates the mass extinction and that Deccan volcanism and its environmental consequences were the most likely major cause, but possibly exacerbated by the impact.
The term iridium anomaly commonly refers to an unusual abundance of the chemical element iridium in a layer of rock strata at the Cretaceous–Paleogene (K–Pg) boundary. The unusually high concentration of a rare metal like iridium is often taken as evidence for an extraterrestrial impact event.
The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K–T) boundary, is a geological signature, usually a thin band of rock containing much more iridium than other bands. The K–Pg boundary marks the end of the Cretaceous Period, the last period of the Mesozoic Era, and marks the beginning of the Paleogene Period, the first period of the Cenozoic Era. Its age is usually estimated at around 66 million years, with radiometric dating yielding a more precise age of 66.043 ± 0.011 Ma.
The Baptistina family is an asteroid family of more than 2500 members that was probably produced by the breakup of an asteroid 170 km (110 mi) across 80 million years ago following an impact with a smaller body. The two largest presumed remnants of the parent asteroid are main-belt asteroids 298 Baptistina and 1696 Nurmela. The Baptistina family is part of the larger Flora clan. It was briefly speculated that the Chicxulub impactor was part of the Baptistina family of asteroids, but this was disproven in 2011 using data from the Wide-field Infrared Survey Explorer (WISE).
The climate across the Cretaceous–Paleogene boundary is very important to geologic time as it marks a catastrophic global extinction event. Numerous theories have been proposed as to why this extinction event happened including an asteroid known as the Chicxulub asteroid, volcanism, or sea level changes. While the mass extinction is well documented, there is much debate about the immediate and long-term climatic and environmental changes caused by the event. The terrestrial climates at this time are poorly known, which limits the understanding of environmentally driven changes in biodiversity that occurred before the Chicxulub crater impact. Oxygen isotopes across the K–T boundary suggest that oceanic temperatures fluctuated in the Late Cretaceous and through the boundary itself. Carbon isotope measurements of benthic foraminifera at the K–T boundary suggest rapid, repeated fluctuations in oceanic productivity in the 3 million years before the final extinction, and that productivity and ocean circulation ended abruptly for at least tens of thousands of years just after the boundary, indicating devastation of terrestrial and marine ecosystems. Some researchers suggest that climate change is the main connection between the impact and the extinction. The impact perturbed the climate system with long-term effects that were much worse than the immediate, direct consequences of the impact.
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary(K–T)extinction, was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs. Most other tetrapods weighing more than 25 kilograms also became extinct, with the exception of some ectothermic species such as sea turtles and crocodilians. It marked the end of the Cretaceous Period, and with it the Mesozoic era, while heralding the beginning of the Cenozoic era, which continues to this day.
T. rex and the Crater of Doom is a nonfiction book by professor Walter Alvarez that was published by Princeton University Press in 1997. The book discusses the research and evidence that led to the creation of the Alvarez hypothesis, which explains how an impact event was the main cause that resulted in the Cretaceous–Paleogene extinction event.
Since the 19th century, a significant amount of research has been conducted on the Cretaceous–Paleogene extinction event, the mass extinction that ended the dinosaur-dominated Mesozoic Era and set the stage for the Age of Mammals, or Cenozoic Era. A chronology of this research is presented here.
Chicxulub Puerto is a small coastal town in Progreso Municipality in the Mexican state of Yucatán. It is located on the Gulf of Mexico, in the northwestern region of the state about 8 km east of the city port of Progreso, the municipality seat, and 42 km north of the city of Mérida, the state capital. According to the INEGI census conducted in 2020, the port town had a population of 7,591 inhabitants.
References
- ↑ "Alan Hildebrand home page at The University of Calgary". Archived from the original on 2020-03-13. Retrieved 2020-09-20.
- 1 2 Collins, G. S.; et al. (2020). "A steeply-inclined trajectory for the Chicxulub impact". Nature Communications. 11 (1): 1480. doi:10.1038/s41467-020-15269-x. PMC 7251121 . PMID 32457325.
- 1 2 Hildebrand, Alan Russell encyclopedia.com
- ↑ PTYS/LPL Alumni Directory: Hildebrand, Alan University of Arizona Lunar and Planetary Laboratory
- ↑ Chicxulub Crater where the fate of the dinosaurs was sealed Atlas Obscura
- ↑ Morgan, Jo; Warner, Mike; The Chicxulub Working Group; Brittan, John; Buffler, Richard; Camargo, Antonio; Christeson, Gail; Denton, Paul; Hildebrand, Alan; Hobbs, Richard; MacIntyre, Hamish; MacKenzie, Graeme; Maguire, Peter; Marin, Luis; Nakamura, Yosio; Pilkington, Mark; Sharpton, Virgil; Snyder, Dave; Suarez, Gerardo; Trejo, Alberto (1997). "Size and morphology of the Chicxulub impact crater". Nature. 390 (6659): 472–476. doi:10.1038/37291. S2CID 4398542.