Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay. The use of radiometric dating was first published in 1907 by Bertram Boltwood and is now the principal source of information about the absolute age of rocks and other geological features, including the age of fossilized life forms or the age of Earth itself, and can also be used to date a wide range of natural and man-made materials.
The Archean Eon, in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history, preceded by the Hadean Eon and followed by the Proterozoic. The Archean represents the time period from 4,031 to 2,500 Ma. The Late Heavy Bombardment is hypothesized to overlap with the beginning of the Archean. The Huronian glaciation occurred at the end of the eon.
A calcium–aluminium-rich inclusion or Ca–Al-rich inclusion (CAI) is a submillimeter- to centimeter-sized light-colored calcium- and aluminium-rich inclusion found in carbonaceous chondrite meteorites. The four CAIs that have been dated using the Pb-Pb chronometer yield a weighted mean age of 4567.30 ± 0.16 Myr. As CAIs are the oldest dated solids, this age is commonly used to define the age of the Solar System.
Planetary geology, alternatively known as astrogeology or exogeology, is a planetary science discipline concerned with the geology of celestial bodies such as planets and their moons, asteroids, comets, and meteorites. Although the geo- prefix typically indicates topics of or relating to Earth, planetary geology is named as such for historical and convenience reasons; due to the types of investigations involved, it is closely linked with Earth-based geology. These investigations are centered around the composition, structure, processes, and history of a celestial body.
The Mesoarchean is a geologic era in the Archean Eon, spanning 3,200 to 2,800 million years ago, which contains the first evidence of modern-style plate subduction and expansion of microbial life. The era is defined chronometrically and is not referenced to a specific level in a rock section on Earth.
Geobiology is a field of scientific research that explores the interactions between the physical Earth and the biosphere. It is a relatively young field, and its borders are fluid. There is considerable overlap with the fields of ecology, evolutionary biology, microbiology, paleontology, and particularly soil science and biogeochemistry. Geobiology applies the principles and methods of biology, geology, and soil science to the study of the ancient history of the co-evolution of life and Earth as well as the role of life in the modern world. Geobiologic studies tend to be focused on microorganisms, and on the role that life plays in altering the chemical and physical environment of the pedosphere, which exists at the intersection of the lithosphere, atmosphere, hydrosphere and/or cryosphere. It differs from biogeochemistry in that the focus is on processes and organisms over space and time rather than on global chemical cycles.
The Great Oxidation Event (GOE) or Great Oxygenation Event, also called the Oxygen Catastrophe, Oxygen Revolution, Oxygen Crisis or Oxygen Holocaust, was a time interval during the Early Earth's Paleoproterozoic era when the Earth's atmosphere and the shallow ocean first experienced a rise in the concentration of oxygen. This began approximately 2.460–2.426 Ga (billion years) ago during the Siderian period and ended approximately 2.060 Ga ago during the Rhyacian. Geological, isotopic, and chemical evidence suggests that biologically produced molecular oxygen (dioxygen or O2) started to accumulate in Earth's atmosphere and changed it from a weakly reducing atmosphere practically devoid of oxygen into an oxidizing one containing abundant free oxygen, with oxygen levels being as high as 10% of their present atmospheric level by the end of the GOE.
Thomas Edvard "Tom" Krogh, FRSC was a geochronologist and a former curator for the Royal Ontario Museum. He revolutionized the technique of radiometric uranium-lead dating with the development of new laboratory procedures and analytical methodologies. His discoveries have yielded an unprecedented level of precision in the dating of Precambrian rocks. Krogh's techniques have become the international de facto standard. The application of these techniques has provided a detailed understanding of the evolution of the Earth's Precambrian shield areas.
Amino acid dating is a dating technique used to estimate the age of a specimen in paleobiology, molecular paleontology, archaeology, forensic science, taphonomy, sedimentary geology and other fields. This technique relates changes in amino acid molecules to the time elapsed since they were formed.
Earth science or geoscience includes all fields of natural science related to the planet Earth. This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spheres: the biosphere, hydrosphere/cryosphere, atmosphere, and geosphere. Earth science can be considered to be a branch of planetary science but with a much older history.
The Boring Billion, otherwise known as the Mid Proterozoic and Earth's Middle Ages, is the time period between 1.8 and 0.8 billion years ago (Ga) spanning the middle Proterozoic eon, characterized by more or less tectonic stability, climatic stasis, and slow biological evolution. It is bordered by two different oxygenation and glacial events, but the Boring Billion itself had very low oxygen levels and no evidence of glaciation.
The International Association of Geoanalysts is an international not-for-profit learned society. Its objectives are to: "serve as an international forum for the advancement of geoanalytical science and to promote the interests and support the professional needs of those involved in the analysis of geological and environmental materials".
Provenance in geology, is the reconstruction of the origin of sediments. The Earth is a dynamic planet, and all rocks are subject to transition between the three main rock types: sedimentary, metamorphic, and igneous rocks. Rocks exposed to the surface are sooner or later broken down into sediments. Sediments are expected to be able to provide evidence of the erosional history of their parent source rocks. The purpose of provenance study is to restore the tectonic, paleo-geographic and paleo-climatic history.
Robbie Rice Gries is an American petroleum geologist who was the first female president (2001–02) of the American Association of Petroleum Geologists (AAPG), president of the Geological Society of America (2018–19), and founder of Priority Oil & Gas LLC. Gries is noted to have made some influential progress for women in this field. In 2017, Gries published the book titled Anomalies—Pioneering Women in Petroleum Geology: 1917-2017. Gries is recognized as an unconventional thinker when approaching geological concepts and applications.
Julie Brigham-Grette is a glacial geologist and a professor in the Department of Geosciences at the University of Massachusetts Amherst where she co-directs the Joseph Hartshorn Quaternary Laboratory. Her research expertise is in glacial geology and paleoclimatology; she has made important contributions to Arctic marine and terrestrial paleoclimate records of late Cenozoic to recent, the evolution of the Arctic climate, especially in the Beringia/Bering Strait region, and was a leader of the international Lake El’gygytgyn Drilling Project in northeastern Russia.
Celina A. Suarez is an American geologist. She is known for her research on using trace element and stable isotope geochemistry of fossil vertebrates and invertebrates to understand paleoecology, paleoclimatology, and taphonomy of ancient terrestrial ecosystems. She is an associate profession in the Department of Geosciences at the University of Arkansas. The dinosaur Geminiraptor suarezarum is named after Suarez and her twin sister, Marnia Suarez, co-discovers of the site on which it was found.
Anita Lizzie Grunder is geologist known for her research on volcanic rocks and defining changes in volcanism over geologic eras. She is an elected fellow of the Geological Society of America.
Laura J. Crossey is an American hydrologist and geochemist and Distinguished Professor of Earth and Planetary Sciences at the University of New Mexico (UNM). Crossey is part of UNM's Sustainable Water Resources Grand Challenge team, which studies water and climate in New Mexico and other arid regions. She has studied springs and groundwater in areas including the Western Desert of Egypt, Australia's Great Artesian Basin, Tibet, the Middle Rio Grande Basin and the Grand Canyon.
Keiko Hattori is a geochemist and mineralogist. She is Distinguished University Professor of Geochemistry and Mineral Deposits in the Department of Earth and Environmental Sciences at the University of Ottawa.
