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Chicxulub Crater
The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is offshore, but the crater is named after the onshore community of Chicxulub Pueblo (not the larger coastal town of Chicxulub Puerto). It was formed slightly over 66 million years ago when an asteroid, about in diameter, struck Earth. The crater is estimated to be in diameter and in depth. It is believed to be the second largest impact structure on Earth, and the only one whose peak ring is intact and directly accessible for scientific research. The crater was discovered by Antonio Camargo and Glen Penfield, geophysicists who had been looking for petroleum in the Yucatán Peninsula during the late 1970s. Penfield was initially unable to obtain evidence that the geological feature was a crater and gave up his search. Later, through contact with Alan R. Hildebrand in 1990, Penfield obtained samples that suggested it was an impact feature. Evidence for the crater's imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States's civil list of government space agencies, space program, aeronautics research and outer space, space research. National Aeronautics and Space Act, Established in 1958, it succeeded the National Advisory Committee for Aeronautics (NACA) to give the American space development effort a distinct civilian orientation, emphasizing peaceful applications in space science. It has since led most of America's space exploration programs, including Project Mercury, Project Gemini, the 1968–1972 Apollo program missions, the Skylab space station, and the Space Shuttle. Currently, NASA supports the International Space Station (ISS) along with the Commercial Crew Program and oversees the development of the Orion (spacecraft), Orion spacecraft and the Sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Impact Craters On Earth
This list of impact structures (including impact craters) on Earth contains the majority of the 194+ confirmed impact structures given in the Earth Impact Database as of 2024. Alphabetical lists for different continents can be found under Impact structures by continent below. Unconfirmed structures can be found at List of possible impact structures on Earth. Confirmed impact structures listed by size and age These features were caused by the collision of meteors (consisting of large fragments of asteroids) or comets (consisting of ice, dust particles and rocky fragments) with the Earth. For eroded or buried craters, the stated diameter typically refers to the best available estimate of the original rim diameter, and may not correspond to present surface features. Time units are either in ka (thousands) or Ma (millions) of years. 10 ka or less Less than ten thousand years old, and with a diameter of or more. The EID lists fewer than ten such craters, and the largest in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Luis Walter Alvarez
Luis Walter Alvarez (June 13, 1911 – September 1, 1988) was an American experimental physicist, inventor, and professor who was awarded the Nobel Prize in Physics in 1968 for his discovery of resonance (particle physics), resonance states in particle physics using the Bubble chamber, hydrogen bubble chamber. In 2007 the ''American Journal of Physics'' commented, "Luis Alvarez was one of the most brilliant and productive experimental physicists of the twentieth century." After receiving his PhD from the University of Chicago in 1936, Alvarez went to work for Ernest Lawrence at the Lawrence Berkeley National Lab, Radiation Laboratory at the University of California, Berkeley. Alvarez devised a set of experiments to observe K-electron capture in radioactivity, radioactive nuclei, predicted by the beta decay theory but never before observed. He produced tritium using the cyclotron and measured its lifetime. In collaboration with Felix Bloch, he measured the Neutron magnetic momen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nobel Prize
The Nobel Prizes ( ; ; ) are awards administered by the Nobel Foundation and granted in accordance with the principle of "for the greatest benefit to humankind". The prizes were first awarded in 1901, marking the fifth anniversary of Alfred Nobel, Alfred Nobel's death. The original Nobel Prizes covered five fields: Nobel Prize in Physics, physics, Nobel Prize in Chemistry, chemistry, Nobel Prize in Physiology or Medicine, physiology or medicine, Nobel Prize in Literature, literature, and Nobel Peace Prize, peace, specified in Nobel's will. A sixth prize, the Nobel Memorial Prize in Economic Sciences, Prize in Economic Sciences, was established in 1968 by Sveriges Riksbank (Sweden's central bank) in memory of Alfred Nobel. The Nobel Prizes are widely regarded as the most prestigious awards available in their respective fields.Nobel Prize#Shalev69, Shalev, p. 8. Except in extraordinary circumstances, such as war, all six prizes are given annually. Each recipient, known as a laur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Walter Alvarez
Walter Alvarez (born October 3, 1940) is a professor in the Earth and Planetary Science department at the University of California, Berkeley. He and his father, Nobel Prize–winning physicist Luis Alvarez, developed the theory that dinosaurs were killed by an asteroid impact. Biography Born in Berkeley, California, Alvarez is the son of Luis Walter Alvarez, a Nobel Prize-winner in physics, and Geraldine Smithwick. His grandfather was physician Walter C. Alvarez and his great-grandfather, Spanish-born Luis F. Alvarez, worked as a doctor in Hawaii and developed a method for the better diagnosis of macular leprosy. His great-aunt Mabel Alvarez was an artist and oil painter from California. Alvarez earned his B.A. in geology in 1962 from Carleton College in Minnesota and Ph.D. in geology from Princeton University in 1967. He worked for American Overseas Petroleum Limited in the Netherlands, and in Libya at the time of Colonel Gaddafi's revolution. Having developed a side i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutionary history, evolution of dinosaurs is a subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya and their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, Evolution of birds, having evolved from earlier Theropoda, theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and the extinct non-avian dinosaurs, which are all dinosaurs other than birds. Dinosaurs are varied from taxonomy (biology), taxonomic, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass Extinction
An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the background extinction rate and the rate of speciation. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from disagreement as to what constitutes a "major" extinction event, and the data chosen to measure past diversity. The "Big Five" mass extinctions In a landmark paper published in 1982, Jack Sepkoski and David M. Raup identified five particular geological intervals with excessive diversity loss. They were originally identified as outliers on a general trend of decreasing extinction rates during the Phanerozoic, but as more stringent statistical tests have been applie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cretaceous–Paleogene Extinction Event
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the K–T extinction, was the extinction event, 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 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 current era, the Cenozoic. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the Cretaceous–Paleogene boundary, K–Pg boundary or K–T boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows unusually high levels of the metal iridium, which is more common in asteroids than in the Earth's crust. As originally proposed in 1980 by a team of scientists le ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Winter
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 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 (55 pounds). Possibility of impact Each year, the Earth is hit by diameter meteoroids that deliver ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tektite
Tektites () are gravel-sized bodies composed of black, green, brown or grey natural glass formed from terrestrial debris ejected during meteorite impacts. The term was coined by Austrian geologist Franz Eduard Suess (1867–1941), son of Eduard Suess. They generally range in size from millimetres to centimetres. Millimetre-scale tektites are known as microtektites.French, B. M. (1998) ''Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures.'' LPI Contribution No. 954. Lunar and Planetary Institute, Houston, Texas. 120 pp.McCall, G. J. H. (2001) ''Tektites in the Geological Record: Showers of Glass from the Sky.'' The Geological Society Publishing House, Bath, United Kingdom. 256 pp. Montanari, A., and C. Koeberl (2000) ''Impact Stratigraphy. The Italian Record.'' Lecture Notes in Earth Sciences Series no. 93. Springer-Verlag, New York, New York. 364 pp. Tektites are characterized by: # a fairly homogeneous composition # an ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravity Anomaly
The gravity anomaly at a location on the Earth's surface is the difference between the observed value of gravity and the value predicted by a theoretical model. If the Earth were an ideal oblate spheroid of uniform density, then the gravity measured at every point on its surface would be given precisely by a simple algebraic expression. However, the Earth has a rugged surface and non-uniform composition, which distorts its gravitational field. The theoretical value of gravity can be corrected for altitude and the effects of nearby terrain, but it usually still differs slightly from the measured value. This gravity anomaly can reveal the presence of subsurface structures of unusual density. For example, a mass of dense ore below the surface will give a positive anomaly due to the increased gravitational attraction of the ore. Different theoretical models will predict different values of gravity, and so a gravity anomaly is always specified with reference to a particular model. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shocked Quartz
Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure (but limited temperature), the crystalline structure of quartz is deformed along planes inside the crystal. These planes, which show up as lines under a microscope, are called planar deformation features (PDFs), or shock lamellae. Discovery Shocked quartz was discovered following underground nuclear weapons testing, which generated the intense pressures required to alter the quartz lattice. Eugene Shoemaker showed that shocked quartz is also found inside craters created by meteor impact, such as the Barringer Crater and Chicxulub crater. The presence of shocked quartz supports that such craters were formed by impact, because a volcanic eruption would not generate the required pressure. Lightning is now known to contribute to the surface record of shocked quartz grains, complicating identification of hypervelocity impact features. Formation Shocke ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
