# Glossary of geology terms
## Glossary of Geology Terms

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Aphanitic – refers to the texture of igneous rocks when you can’t distinguish individual minerals unless you use a microscope then it is said to have an aphanitic texture. (H. Redoble)
Asthenosphere - the layer of the mantle that lies directly below the lithosphere. (A.Senos)
Carbonate - minerals that contain the carbonate anion ((CO3)2-), some of the most common include aragonite, calcite and magnesite. (A. Senos)
Cleavage - When a mineral is broken, cleavage is shown by the pattern in which it breaks along crystallographic planes. If it does not follow these planes then it is considered a fracture. (T. Bakic)
Continental volcanic arch - mountain ranges produced by igneous activity due to the subduction of the ocean's lithosphere.
Curie Point - The temperature a substance reaches when its magnetism is lost. (J.Mellum)
Geology - the study of the earth. Physical Geology includes processes that affect the earth's internal and external structure, composition and other natural functions. Historical Geology is the study of Earth history and the evolution of life on earth - especially the past life forms that are preserved as fossils. (J.Wittstrom)
Erosion - The transportation of material by a mobile agent, i.e., water, wind or ice.(C Simoneau)
Evaporite - Sedimentary rocks made up of minerals that are deposited from the precipitation of evaporated seawater. (M. MacFadzen)
Fracture - when a mineral breaks and does not cleave the mineral fractures. Fractures can be irregular, curved, jagged or splintery. Quartz actually has a conchoidal fracture which is dish shaped. (H. Redoble)
Halide - a binary compound constructed of two parts, one halogen atom and one element or radical that has a electronegative value less than the halogen. (Q.Janmohamed)
Hardness - A property of a mineral. Its tolerance or resistance to scratching or abrasion. This is measured by the Moh's scale. (Christine Simoneau)
Harry Hess - In the 1960s Hess developed the theory that the seafloor is spreading. This theory was based on the discovery of the Mid-Atlantic Ridge, proving that the upwelling of magma breaking through the mantle is pushing the seafloor from the ridge crest.(J.Howley)
Hot Spot- A stationary mantle plume which will form a series of volcanoes or sea mountains as the earth's crust moves over it. (M.Laery)
Lithosphere - located above the asthenosphere, the lithosphere consists of the outer layer of earth’s crust and upper mantle. The lithosphere also contains the Moho boundary. (H.Redoble)
Lustre- the reflective quality of light on the freshly broken surface of a mineral. The main divisions of lustre are metallic and non-metallic. (M. MacFadzen)
Magma - A body of molten rock found at depth. (C Simoneau)
Magnetometer - Am instrument used for measuring a magnetic field's magnitude and direction. (T. Bakic)
Moho boundary - Formally called the Mohorovičić discontinuity is the boundary between the Earth's crust and mantle.
Native Element - occurs in nature and is not part of a compound. Examples are gold and silver. (J. Mellum)
Paleomagnetism - Refers to the study of the magnetic properties of rocks and minerals. This demonstrates to us that both the strength and direction of Earths magnetic field is not constant. Each rock and mineral tells its own story at a particular moment in time. (A. Atwal)
Pegmatite - A very coarse grained igneous rock like granite; commonly associated with large masses of plutonic rock. (M. MacFadzen)
Spreading Ridge - an elevated region where new crust material is being formed and where older crust moves away from the ridge. (B.Qaderi)
Volcanic Island Arcs - When either oceanic crust subducts under oceanic crust (oceanic arc) or continental crust subducts under continental crust (continental arc). (Q.Janmohamed)
Xenolith - fragments of country rock (detatched by stoping) that sink into the magma. They are not fully absorbed by the magma and so remain as a mass. Some can be seen in igneous rocks.
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