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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.
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Sumio Iijima is a Japanese physicist and inventor, often cited as the inventor of carbon nanotubes. Although carbon nanotubes had been observed prior to his "invention", Iijima's 1991 paper generated unprecedented interest in the carbon nanostructures and has since fueled intense research in the area of nanotechnology.
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.
Wilkes Land crater is an informal term that may apply to two separate cases of conjectured giant impact craters hidden beneath the ice cap of Wilkes Land, East Antarctica. These are separated below under the heading Wilkes Land anomaly and Wilkes Land mascon , based on terms used in their principal published reference sources.
The history of nanotechnology traces the development of the concepts and experimental work falling under the broad category of nanotechnology. Although nanotechnology is a relatively recent development in scientific research, the development of its central concepts happened over a longer period of time. The emergence of nanotechnology in the 1980s was caused by the convergence of experimental advances such as the invention of the scanning tunneling microscope in 1981 and the discovery of fullerenes in 1985, with the elucidation and popularization of a conceptual framework for the goals of nanotechnology beginning with the 1986 publication of the book Engines of Creation. The field was subject to growing public awareness and controversy in the early 2000s, with prominent debates about both its potential implications as well as the feasibility of the applications envisioned by advocates of molecular nanotechnology, and with governments moving to promote and fund research into nanotechnology. The early 2000s also saw the beginnings of commercial applications of nanotechnology, although these were limited to bulk applications of nanomaterials rather than the transformative applications envisioned by the field.
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 Cretaceous–Paleogene (K–Pg) extinction event was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the exception of some ectothermic species such as sea turtles and crocodilians, no tetrapods weighing more than 25 kilograms survived. 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.
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.
Techniques have been developed to produce carbon nanotubes in sizable quantities, including arc discharge, laser ablation, high-pressure carbon monoxide disproportionation, and chemical vapor deposition (CVD). Most of these processes take place in a vacuum or with process gases. CVD growth of CNTs can occur in vacuum or at atmospheric pressure. Large quantities of nanotubes can be synthesized by these methods; advances in catalysis and continuous growth are making CNTs more commercially viable.
Alan Russell Hildebrand is a planetary scientist and Associate Professor in the Department of Geoscience at the University of Calgary. He has specialized in the study of asteroid impact cratering, fireballs and meteorite recovery. His work has shed light on the extinction event caused by the Chicxulub asteroid at the end of the Cretaceous period. Hildebrand is one of the leaders of the Prairie Meteorite Network search project.
The Nadir crater is an undersea feature on the Guinea Plateau in the Atlantic Ocean, 248 mi (400 km) off the coast of Guinea. It is suggested to be an impact crater. The feature is named after the Nadir Seamount, located 100 km to the south, and is around 8.5-km-wide. The paper announcing the discovery of the feature was published in Science Advances in 2022. It has been proposed that the structure be drilled to confirm/disprove the impact origin.
References
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- ↑ Balbus, Steven A.; Hawley, John F. (1991). "A powerful local shear instability in weakly magnetized disks". The Astrophysical Journal . 376: 214–233. Bibcode:1991ApJ...376..214B. doi:10.1086/170270.
- ↑ Iijima, Sumio (7 November 1991). "Helical microtubules of graphitic carbon". Nature . 354 (6348): 56–58. Bibcode:1991Natur.354...56I. doi:10.1038/354056a0. S2CID 4302490.
- ↑ Monthioux, Marc; Kuznetsov, Vladimir L. (2006). "Who should be given the credit for the discovery of carbon nanotubes?" (PDF). Carbon. 44 (9): 1621. doi:10.1016/j.carbon.2006.03.019 . Retrieved 2012-02-03.
- ↑ Zimmermann, Philip (2001-06-05). "PGP Marks 10th Anniversary" . Retrieved 2012-01-28.
- ↑ "Welcome to info.cern.ch, the website of the world's first-ever web server". CERN. Archived from the original on 27 May 2008. Retrieved 25 May 2008.
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- ↑ Pope, Kevin O.; et al. (9 May 1991). "Mexican site for K/T impact crater?". Nature . 351 (6322): 105. Bibcode:1991Natur.351..105P. doi:10.1038/351105a0. S2CID 36707836.
- ↑ Hildebrand, Alan R.; Penfield, Glen T.; Kring, David A.; Pilkington, Mark; Zanoguera, Antonio Camargo; Jacobsen, Stein B.; Boynton, William V. (September 1991). "Chicxulub Crater: a possible Cretaceous/Tertiary Boundary impact crater on the Yucatán Peninsula, Mexico". Geology . 19 (9): 867–871. Bibcode:1991Geo....19..867H. doi:10.1130/0091-7613(1991)019<0867:CCAPCT>2.3.CO;2.
- ↑ Schulte, Peter; et al. (2010). "The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous- Paleogene Boundary" (PDF). Science . 327 (5970): 1214–1218. Bibcode:2010Sci...327.1214S. doi:10.1126/science.1177265. PMID 20203042. S2CID 2659741.
- ↑ Candelas, Philip; de la Ossa, Xenia; Green, Paul; Parks, Linda (1991). "A pair of Calabi–Yau manifolds as an exactly soluble superconformal field theory". Nuclear Physics B . 359 (1): 21–74. Bibcode:1991NuPhB.359...21C. doi:10.1016/0550-3213(91)90292-6.
- ↑ Wang, Qiudong (1991). "The global solution of the n-body problem". Celestial Mechanics and Dynamical Astronomy . 50 (1): 73–88. Bibcode:1991CeMDA..50...73W. doi:10.1007/BF00048987. ISSN 0923-2958. S2CID 118132097.