Ultramafic Definition
In the study of geology, the term “ultramafic” refers to an igneous rock that comprises up to 90% mafic minerals, or more.
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Focus (Hypocenter)
Focus (Hypocenter) Focus (Hypocenter): In the seismology branch of geology, a focus, or hypocenter, refers to the specific place where an earthquake rupture originates. The focus, or hypocenter, underlies the epicenter when an earthquake occurs at a dip-slip fault, strike-slip fault, oblique-slip fault, or listric fault. In the event of an earthquake, geologists, and seismologists…
Oblique-Slip Fault Definition
Oblique-Slip Fault Oblique-Slip Fault: In geology, an oblique-slip fault is a fault that moves parallel to the strike or dip of the fault plane.
Regression
Regression Regression: In geology, regression is the formation of a specific sequence of sedimentary and metamorphic layers, that are the result of ocean water withdrawing from the land. To illustrate, when regression occurs over millions of years, geologists find a layer of limestone, overlain by shale, and overlain again by limestone. The opposite of regression is…
Twinning Definition
Twinning Definition Twinning is the observed intergrowth of multiple crystals in a symmetrical fashion. This term applies to the examination of rock thin sections, in the field of optical mineralogy.
Regional Metamorphism
Regional Metamorphism Regional Metamorphism: Metamorphism acts over large areas resulting from applied pressures of 3,000 to 10,000 bars and temperatures of 400°C to 800°C. Regional metamorphism is also referred to as dynamothermal metamorphism.
