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Geology is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth sciences, including hydrology and the atmospheric sciences, and so is treated as one major aspect of integrated Earth system science and planetary science.
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.
The age of Earth is estimated to be 4.54 ± 0.05 billion years (4.54 × 109 years ± 1%). This age may represent the age of Earth's accretion, or core formation, or of the material from which Earth formed. This dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.
Petrology is the branch of geology that studies rocks and the conditions under which they form. Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. Igneous and metamorphic petrology are commonly taught together because they both contain heavy use of chemistry, chemical methods, and phase diagrams. Sedimentary petrology is, on the other hand, commonly taught together with stratigraphy because it deals with the processes that form sedimentary rock.
The Sudbury Basin, also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geological structure in Ontario, Canada. It is the third-largest known impact crater or astrobleme on Earth, as well as one of the oldest. The crater formed 1.849 billion years ago in the Paleoproterozoic era.
Paleomagnetism, or palaeomagnetism, is the study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials. Magnetic minerals in rocks can lock-in a record of the direction and intensity of the magnetic field when they form. This record provides information on the past behavior of Earth's magnetic field and the past location of tectonic plates. The record of geomagnetic reversals preserved in volcanic and sedimentary rock sequences (magnetostratigraphy) provides a time-scale that is used as a geochronologic tool. Geophysicists who specialize in paleomagnetism are called paleomagnetists.
Variolites are mafic, igneous, and typically volcanic rocks, e.g. tholeiite, basalt or komatiite, that contain centimeter-scale spherical or globular structures, called varioles, in a fine-grained matrix. These structures are lighter colored than the host rock and typically range in diameter from 0.05mm to over 5 cm. In 1648, Aldrovandi created the term variolite for aphanitic or fine-grained igneous rocks containing varioles. The weathering of varioles often cause variolites to have a pock-marked appearance. In allusion to the pock-marked appearance of weathered surfaces of variolite, this term is derived from the Latin word, variola, for smallpox.
Komatiite is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava of at least 18 wt% MgO. Komatiites have low silicon, potassium and aluminium, and high to extremely high magnesium content. Komatiite was named for its type locality along the Komati River in South Africa, and frequently displays spinifex texture composed of large dendritic plates of olivine and pyroxene.
Plutonism is the geologic theory that the igneous rocks forming the Earth originated from intrusive magmatic activity, with a continuing gradual process of weathering and erosion wearing away rocks, which were then deposited on the sea bed, re-formed into layers of sedimentary rock by heat and pressure, and raised again. It proposes that basalt is solidified molten magma. The theory lead to plutonic (intrinsic) rock classification, which includes intrinsic igneous rocks such as Gabbro, Diorite, Granite and Pegmatite. The name Plutonism references Pluto, the classical ruler of the underworld and the Roman god of wealth. A main reason Pluto was incorporated into the classification was due to the Plutonic rocks commonly being present in Gold and Silver Ore deposits (veins).
The geology of Scotland is unusually varied for a country of its size, with a large number of differing geological features. There are three main geographical sub-divisions: the Highlands and Islands is a diverse area which lies to the north and west of the Highland Boundary Fault; the Central Lowlands is a rift valley mainly comprising Palaeozoic formations; and the Southern Uplands, which lie south of the Southern Uplands Fault, are largely composed of Silurian deposits.
Various theories of ore genesis explain how the various types of mineral deposits form within the Earth's crust. Ore-genesis theories vary depending on the mineral or commodity examined.
In geology, an igneous intrusion is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and compositions, illustrated by examples like the Palisades Sill of New York and New Jersey; the Henry Mountains of Utah; the Bushveld Igneous Complex of South Africa; Shiprock in New Mexico; the Ardnamurchan intrusion in Scotland; and the Sierra Nevada Batholith of California.
The history of geology is concerned with the development of the natural science of geology. Geology is the scientific study of the origin, history, and structure of Earth.
The Palisades Sill is a Triassic, 200 Ma diabase intrusion. It extends through portions of New York and New Jersey. It is most noteworthy for The Palisades, the cliffs that rise steeply above the western bank of the Hudson River. The ideal location and accessibility of the sill, as well as its unique features, have generated much attention from nature enthusiasts, rock climbers, and geologists alike.
Nickel–Strunz classification is a scheme for categorizing minerals based upon their chemical composition, introduced by German mineralogist Karl Hugo Strunz in his Mineralogische Tabellen (1941). The 4th and the 5th edition was also edited by Christel Tennyson (1966). It was followed by A.S. Povarennykh with a modified classification.
A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, although backgrounds in physics, chemistry, biology, and other sciences are also useful. Field research is an important component of geology, although many subdisciplines incorporate laboratory and digitalised work.
Halide minerals are those minerals with a dominant halide anion. Complex halide minerals may also have polyatomic anions.
Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava.