Structural geology Structural geology Amphibolite is the name given to a rock consisting mainly of hornblende amphibole, the use of the term being restricted, however, to metamorphic rocks. The modern terminology for a holocrystalline plutonic igneous rocks rock composed primarily of hornblende amphibole is a hornblendite, which are usually crystal cumulates. Rocks with >90% amphibole which have a feldspar groundmass may be a lamprophyre. ...more on Wikipedia about "Amphibolite"
In geology, an anticline is a type of fold that involves a downward slope to either side. It is an upward-curved structure. In an eroded anticline the oldest rock layers are in the center and the rocks on either side dip or slope away from the center. Folds, and thus anticlines, typically form during crustal deformation as the result of compression that accompanies orogenic mountain building. ...more on Wikipedia about "Anticline"
The Basin and Range Province is a particular type of topography that covers much of the southwestern United States and northwestern Mexico that is typified by elongate north-south trending arid valleys bounded by mountain ranges which also bound adjacent valleys. Death Valley is a good example of a modified basin and range valley. ...more on Wikipedia about "Basin and Range"
(Boudinage)
Etymology
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A creepmeter is an instrument that monitors the slow surface displacement of an active geologic fault in the earth. Its function is to record the slow, a seismic slip between earthquakes. The measurement range of a creepmeter is usually limited to 10-30 mm. Approximately 30 creepmeters are in operation in California - most are operated by the United States Geological Survey (USGS), but nine are maintained by the University of Colorado. ...more on Wikipedia about "Creepmeter"
Crenulation is a texture formed in metamorphic rocks such as phyllite, schist and some gneiss by two or more stress directions resulting in superimposed foliations. ...more on Wikipedia about "Crenulation"
A diapir is an intrusion caused by buoyancy and pressure differentials. Diapirs may include igneous structures, but are more commonly applied to non-igneous, relatively cold materials, such as salt domes and mud diapirs. A diapir is any relatively mobile mass that intrudes into preexisting strata. Diapirs commonly intrude vertically upward along fractures or zones of structural weakness through more dense overlying rocks because of buoyancy forces associated with relatively low-density rock types, such as evaporite salt deposits, and gas charged muds. All of which form diapirs. The process is known as diapirism. The resulting structures are also referred to as piercement structures. Explosive, hot volatile rich magma or volcanic eruptions are referred to generally as diatremes. ...more on Wikipedia about "Diapir"
Fault mechanics is a field of study that investigates the behavior of geologic faults. ...more on Wikipedia about "Fault mechanics"
A fault scarp is an escarpment or apparent step in the ground caused by an active earthquake or by differential erosion along an old inactive fault. Active fault scarps are formed when an earthquake changes the elvation of the ground, and can be caused by any type of fault, including strike-slip faults, whose motion is primarily horizontal. Fault scarps may be only a few centimetres or many metres high. Fault-line scarps are coincident with faults, but are most typically formed by the erosion of weaker rocks that have been brought alongside more resistant ones by the fault's movements. In the case of old eroded fault scarps, active erosion may have moved the physical cliff back away from the actual fault location which may be buried beneath talus or valley fill. ...more on Wikipedia about "Fault scarp"
The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of plastic (i.e. permanent) deformation. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur singly as isolated folds and in extensive fold trains of different sizes, on a variety of scales. ...more on Wikipedia about "Fold (geology)"
Foliation is any penetrative planar fabric present in rocks. Foliation is common to rocks affected by regional metamorphic compression typical of orogenic belts. Rocks exhibiting foliation include the typical metamorphic rock sequence of slate, phyllite, schist and gneiss. The slatey cleavage typical of slate is due to the parallel growth of microscopic mica crystals. In gneiss the foliation is more typically represented by compositional banding due to segregation of mineral phases. Foliated rock is also known as S-tectonite in sheared rock masses. ...more on Wikipedia about "Foliation (geology)"
The Garlock Fault Line is a fault line running approximately northwest- southeast marking the northern boundary of the area known as the Mojave Block, as well as the southern ends of the Sierra Nevada and the valleys of the westernmost Basin and Range province. It intersects the (perhaps better known) San Andreas Fault in Antelope Valley, California. The motion of the Garlock causes deflection in the San Andreas, and deforms it slightly into a curve. The Garlock is the second largest fault in California behind the San Andreas. ...more on Wikipedia about "Garlock Fault"
Geologic faults or simply faults are planar rock fractures which show evidence of relative movement. Large faults within the Earth's crust are the result of shear motion and active fault zones are the causal locations of most earthquakes. Earthquakes are caused by energy release during rapid slippage along faults. The largest examples are at tectonic plate boundaries, but many faults occur far from active plate boundaries. Since faults usually do not consist of a single, clean fracture, the term fault zone is used when referring to the zone of complex deformation associated with the fault plane. ...more on Wikipedia about "Geologic fault"
A shear zone or shear is a wide zone of distributed shearing in rock. Typically this is a type of fault but it may be difficult to place a distinct fault plane into the shear zone. Shear zones can be inches wide, up to several kilometres wide.
...more on Wikipedia about "Geological shear"
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A graben is a depressed block of land bordered by parallel faults. ...more on Wikipedia about "Graben"
Modern petrology defnes a granulite sensuo stricto as a coarse grained, high-grade metamorphic rock composed primarily of pyroxene, plagioclase feldspar and accessory garnet, oxide and amphibole. Granulite is of mafic comosition and may have had a protolith derived from basalt or some intrusive mafic or ultramafic rock. ...more on Wikipedia about "Granulite"
The Great Glen Fault is a long strike-slip fault or ancient transform fault that runs through its namesake the Great Glen (Glen Albyn) in Scotland. However, the fault is actually much longer and over 200 million years old. ...more on Wikipedia about "Great Glen Fault"
The Highland Boundary Fault traverses Scotland from Arran to Stonehaven. It separates two distinctly different physiographic regions: the Highlands from the Midland Valley, but in most places it is only recognisable as a change in topography. ...more on Wikipedia about "Highland Boundary Fault"
A klippe is a geological feature of thrust fault terranes, where a nappe has thrust exotic strata over an area and been removed to leave a form of inlier. ...more on Wikipedia about "Klippe"
Mylonite is a fine-grained, compact rock without cleavage or crystals. It is classified as a metamorphic rock and has a flow texture. ...more on Wikipedia about "Mylonite"
The Oslo Graben or Oslo Rift is a graben formed during a geologic rifting event in Permian time. The rift formation was accompanied by volcanic activity and associated rhomb porphyry lava flows. It is located in the area around the Norwegian capital Oslo. ...more on Wikipedia about "Oslo Graben"
Sandiford M., Hand M., Sandra McLaren, S., 2001. Tectonic feedback, intraplate orogeny and the geochemical structure of the crust: a central Australian perspective. In "Polyphase tectonism and reactivation mechanisms in metamorphic belts", Geological Society of London, Special Publication ...more on Wikipedia about "Petermann Orogeny"
Rhomb porphyry is a volcanic rock with gray-white large porphyritic rhomb shaped phenocrysts enbedded in a very fine grained red-brown matrix. The composition of rhomb porphyry place it in the trachyte - latite classification of the QAPF diagram. ...more on Wikipedia about "Rhomb porphyry"
In geology, a rift is a place where the Earth's crust and lithosphere are being pulled apart. Typical features are a central linear downdropped fault segment, called a graben, with parallel normal faulting and rift-flank uplifts on either side. The axis of the rift area commonly contains volcanic rocks and active volcanism is a part of many but not all active rift systems. Rifts are distinct from Mid-ocean ridges, where new oceanic crust and lithosphere is created by seafloor spreading. In rifts, no crust or lithosphere is produced. If rifting continues, eventually a mid-ocean ridge may form, marking a divergent boundary between two tectonic plates. Failed rifts are ancient to modern features where continental rifting began, but then failed to continue. Typically the transition from rifting to spreading develops as three converging rifts over a hotspot. Two of these evolve to the point of seafloor spreading, while the third ultimately fails, becoming an aulacogen. ...more on Wikipedia about "Rift (geology)"
Rock microstructure includes the texture of a rock and the small scale rock structures. The words "texture" and "microsctructure" are interchangeable, with the latter preferred in modern geological literature. However, texture is still acceptable because it is a useful means of identifying the origin of rocks, how they formed, and their appearance. ...more on Wikipedia about "Rock microstructure"
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