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Iridium Anomaly
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. Anomaly characteristics The type locality of this iridium anomaly is near Raton, New Mexico. Iridium is a very rare element in the Earth's crust, but is found in anomalously high concentrations (around 100 times greater than normal) in a thin worldwide layer of clay marking the boundary between the Cretaceous and Paleogene periods, 66 million years ago. This boundary is marked by a major extinction event, including that of the dinosaurs along with about 70% of all other species. The clay layer also contains small grains of shocked quartz and, in some places, small weathered glass beads thought to be tektites. Meteorite impact theory A team consisting of the physicist Luis Alva ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler substances by any chemical reaction. The number of protons in the nucleus is the defining property of an element, and is referred to as its atomic number (represented by the symbol ''Z'') – all atoms with the same atomic number are atoms of the same element. Almost all of the baryonic matter of the universe is composed of chemical elements (among rare exceptions are neutron stars). When different elements undergo chemical reactions, atoms are rearranged into new compounds held together by chemical bonds. Only a minority of elements, such as silver and gold, are found uncombined as relatively pure native element minerals. Nearly all other naturally occurring elements occur in the Earth as compounds or mixtures. Air is primarily a mixture ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physicist
A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate causes of phenomena, and usually frame their understanding in mathematical terms. Physicists work across a wide range of research fields, spanning all length scales: from sub-atomic and particle physics, through biological physics, to cosmological length scales encompassing the universe as a whole. The field generally includes two types of physicists: experimental physicists who specialize in the observation of natural phenomena and the development and analysis of experiments, and theoretical physicists who specialize in mathematical modeling of physical systems to rationalize, explain and predict natural phenomena. Physicists can apply their knowledge towards solving practical problems or to developing new technologies (also known as app ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eltanin Impact
The Eltanin impact is thought to be an asteroid impact in the eastern part of the South Pacific Ocean that occurred around the Pliocene-Pleistocene boundary approximately 2.51 ± 0.07 million years ago. The location was at the edge of the Bellingshausen Sea southwest of Chile, with a seafloor depth of approximately . The asteroid was estimated to be about in diameter. No crater associated with the impact has been discovered. The impact likely evaporated of water, generating large tsunami waves hundreds of metres high. Description The possible impact site was first discovered in 1981 as an iridium anomaly in sediment cores collected by the research vessel '' Eltanin'', after which the site and impactor are named. Later studies were done by the vessel ''Polarstern''. Sediment at the bottom of the deep ocean in the area had an iridium enrichment, a strong sign of extraterrestrial contamination. Possible debris from the asteroid is spread over an area of . Sediments fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alvarez Hypothesis
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. In March 2010, an international panel of scientists endorsed the asteroid hypothesis, specifically the Chicxulub impact, as being the cause of the extinction. A team of 41 scientists reviewed 20 years of scientific literature and in so doing also ruled out other theories such as massive volcanism. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatemala, Belize, and the Caribbean Sea; and to the east by the Gulf of Mexico. Mexico covers ,Mexico ''''. . making it the world's 13th-largest country by are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yucatán Peninsula
The Yucatán Peninsula (, also , ; es, Península de Yucatán ) is a large peninsula in southeastern 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 peninsula is approximately in area. It has low relief, and is almost entirely composed of porous limestone. The peninsula lies east of the Isthmus of Tehuantepec, the narrowest point in Mexico separating the Atlantic Ocean, including the Gulf of Mexico and Caribbean Sea, from the Pacific Ocean. Some consider the isthmus to be the geographic boundary between Central America and the rest of North America, placing the peninsula in Central America. Politically all of Mexico, including the Yucatán, is generally considered part of North America, while Guatemala an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chicxulub Crater
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 in diameter, struck Earth. The crater is estimated to be in diameter and 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. 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 impact origin includes shocked quartz, a gravity anomaly, and tek ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Lunar impact craters range from microscopic craters on lunar rocks returned by the Apollo Program and small, simple, bowl-shaped depressions in the lunar regolith to large, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth. Impact craters are the dominant geographic features on many solid Solar System objects including the Moon, Mercury, Callisto, Ganymede and most small moons and asteroids. On other planets and moons that experience more active surface geological processes, such as Earth, Venus, Europa, Io and Titan, visible impact craters are less common because they become ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Science (journal)
''Science'', also widely referred to as ''Science Magazine'', is the peer-reviewed academic journal of the American Association for the Advancement of Science (AAAS) and one of the world's top academic journals. It was first published in 1880, is currently circulated weekly and has a subscriber base of around 130,000. Because institutional subscriptions and online access serve a larger audience, its estimated readership is over 400,000 people. ''Science'' is based in Washington, D.C., United States, with a second office in Cambridge, UK. Contents The major focus of the journal is publishing important original scientific research and research reviews, but ''Science'' also publishes science-related news, opinions on science policy and other matters of interest to scientists and others who are concerned with the wide implications of science and technology. Unlike most scientific journals, which focus on a specific field, ''Science'' and its rival ''Nature'' cover the full r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meteorite
A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate energy. It then becomes a meteor and forms a fireball, also known as a shooting star; astronomers call the brightest examples " bolides". Once it settles on the larger body's surface, the meteor becomes a meteorite. Meteorites vary greatly in size. For geologists, a bolide is a meteorite large enough to create an impact crater. Meteorites that are recovered after being observed as they transit the atmosphere and impact the Earth are called meteorite falls. All others are known as meteorite finds. Meteorites have traditionally been divided into three broad categories: stony meteorites t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helen Vaughn Michel
Helen Vaughn Michel (born 1932) is an American chemist best known for her efforts in fields including analytical chemistry and archaeological science, and specific processes such as neutron activation analysis and radiocarbon dating. Her work with Frank Asaro at the Lawrence Berkeley National Laboratory at the University of California (Berkeley) is particularly noteworthy as it includes the dating of Drake's Plate of Brass as well as the Alvarez hypothesis, the hypothesis that posits the Cretaceous–Paleogene extinction event The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the .... Michel retired from the Lawrence Berkeley National Laboratory in 1990. References Living people 1932 births 21st-century American chemists University of California, Berkeley alumni Univers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frank Asaro
Frank Asaro (born Francesco Asaro, July 31, 1927 – June 10, 2014) was an Emeritus Senior Scientist at the Lawrence Berkeley National Laboratory associated with the University of California at Berkeley. He is best known as the chemist who discovered the iridium anomaly in the Cretaceous–Paleogene boundary layer that led the team of Luis Alvarez, Walter Alvarez, Frank Asaro, and Helen Michel to propose the Asteroid-Impact Theory, which postulates that an asteroid hit the Earth sixty-five million years ago and caused mass extinction during the age of the dinosaurs. Biography Asaro grew up in Escondido, California, the son of avocado farmer and barber Nicolo Asaro and Antonina (Annie) Asaro. He married Lucille Marie Lavezo and settled in the California Bay Area. They had four children, Frank, Antonina, Catherine, and Marianna. Asaro's mother, one of the oldest known residents of Escondido, lived until almost 106 years old. Research The Early Berkeley Years Asaro went to c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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