Structural geology

fracture or discontinuity in rock across which there is displacement

geological structure

thumb|Cross-sectional diagram of an anticline thumb|Jim Crowley (USGS) standing in front of folded layers of banded iron formation of Hamersley Range, Australia. In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the location where the curvature is greatest, and the limbs are the sides of the fold that dip away from the hinge. Anticlines can be recognized and differentiated from antiforms by a sequence of rock laye

thumb|upright=1.35|Diagram illustrating the structural relationship between grabens and horsts upright=1.35|thumb|Infrared-enhanced satellite image of a graben in the Afar Triangle|Afar Depression

thumb|Block view of a rift formed cut of three segments, showing the location of the accommodation zones between them at changes in fault location or polarity (dip direction). upright|thumb|Gulf of Suez Rift showing main [[extensional faults]]

thumb|A syncline is a fold of rocks with younger rock layers closer to the center of the structure, whereas an anticline is the inverse of a syncline.|right|upright=1.95 In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimposed smaller folds. Synclines are typically a downward fold (synform), termed a synformal syncline (i.e. a trough), but synclines that point upwards can be found when strata have been overtu

science of the description and interpretation of deformation in the earth's crust independent of extent

Raised fault block bounded by normal faults

underground accumulation of molten rock

thumb|Cuesta in Italy thumb|Schematic cross section of three cuestas, dip slopes facing left, and harder rock layers in darker colors than softer ones thumb|Cuesta in Crimea thumb| Magaliesberg Range, Transvaal, South Africa

circular feature in the Sahara desert

right|thumb|250px|A sample of granulite-facies metamorphic rock of felsic composition, with [[garnet porphyroblasts]]

geological depression

a type of reverse fault that has a dip of 45 degrees or less

lava containing characteristic pillow-shaped structures due to subaqueous extrusion

plate boundary where the motion is predominantly horizontal

Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonites can have many different mineralogical compositions; it is a classification based on the textural appearance of the rock.

thumb|400px|Diapirs in a subduction|subducting plate boundary

mountains formed by compressive crumpling of the layers of rock

geological term for a type of fracture in rock

sheetlike body within a rock

repetitive layering in metamorphic rocks

very large block of rock

region surrounding the lowest point on the ridgeline between two elevations; not necessarily navigable

deformational feature in structural geology

thumb|right|350px|Schematic overview of an eroded thrust system. The shaded material is the nappe. The erosional hole is called a window (geology)|window or fenster. The [[klippe is the isolated block of the nappe overlying autochthonous material.]] In geology, a nappe or thrust sheet is a large sheetlike body of rock that has been moved more than or above a thrust fault from its original position. Nappes form in compressional tectonic settings like continental collision zones or on the overriding plate in active subduction zones. Nappes form when a mass of rock is forced (or "thrust") over an

structural geology

thumb|right|Melange from Geology of Narooma|Narooma, [[Australia.]]

A monocline (or, rarely, a monoform) is a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently dipping sequence.

landform of an entrenched transverse valley

thumb|right|upright=1.6|Schematic overview of a thrust system. The hanging wall block is (when it has reasonable proportions) called a nappe. If an [[erosional hole is created in the nappe that is called a window. A klippe is a solitary outcrop of the nappe in the middle of autochthonous material.]]

long, narrow ridge with a narrow crest and steep slopes of nearly equal inclination on both flanks

geologic discontinuity feature, often a diaclase, or a fault

study of salt-controlled structures (like salt domes), mechanisms, and tectonic deformation involving salt or other evaporates

thumb|260px|Diastrophism by 2011 Tohoku earthquake Diastrophism is the process of deformation of the Earth's crust which involves folding and faulting. Diastrophism can be considered part of geotectonics. The word is derived from the Greek '''' 'distortion, dislocation'.

joining together along a major fault zone, of separate terranes, tectonic units that have different plate tectonic, metamorphic and paleogeographic histories

thumb|right|350px|Schematic overview of a thrust system. The shaded material is called a nappe. The erosional hole is called a window or fenster. The klippe is the isolated block of the nappe overlying autochthonous material.

physiographic region extending through much of the western United States and Mexico

diagram of a 2D or 3D cross section through geological structures

thumb|Small-scale boudinage thumb|Boudinaged quartz vein within [[blueschist, Samos, Greece.]] thumb|Boudinage in Greenland near [[Kangerlussuaq]] thumb|upright|Boudinaged Vein (geology)|quartz vein in shear foliation, Starlight Pit, Fortnum Gold Mine, [[Western Australia.]] thumb|upright|Foliation (geology)|Banded [[gneiss with dike of granite orthogneiss; competent banded gneiss is boudinaged by ductile shear.]] thumb|Boudin on the Island of Uto, Stockholm Archipelago, [[Sweden]] thumb|Chocolate-tablet boudinage structures in a low grade metasedimentary rock outcropping in Deception Pass, Wa

eroded area in which a lower geologic unit crops out in the middle of higher units

process that generates seismic waves in an earthquake

small step or offset on the ground surface where one side of a fault has moved vertically with respect to the other

upright=1.35|thumb|right|Stylolites in limestone

type of weathering joint

geological structure where sets of intersecting closely spaced fractures, referred to as joints, result in the formation of a regular array of polygonal prisms, or columns

old and stable part of the continental lithosphere located in Pilbara, Western Australia

See also Line (geometry)

alt=|thumb|322x322px|Purple and green pseudotachylyte veins in outcrop (Sierra Nevada Mountains, California) Pseudotachylyte (sometimes written as pseudotachylite) is an extremely fine-grained to glassy, dark, cohesive rock occurring as veins that form through frictional melting and subsequent quenching during earthquakes, large-scale landslides, and impacts events. Chemical composition of pseudotachylyte generally reflects the local bulk chemistry, though may skew to slightly more mafic compositions due to the preferential incorporation of hydrous and ferro-magnesian minerals (mica and amphib

a formation in which its units are arranged diagonally

A descriptive and nongenetic term for any kind of linear structure within or on a rock

topographic surface which slopes in the same direction as the dip of the underlying strata

thumb|Sample of gold ore from the Red Lake Mine consisting of a stockwork of gold filled veinlets (sample width: 6.6 cm) In geology, a stockwork is a complex system of structurally controlled or randomly oriented veins. Stockworks are common in many ore deposit types and in greisens. They are also referred to as stringer zones.

geologicial processes associated with the stretching of a planetary body's crust

right|thumb|400px| L-S tectonite viewed in the plane of the S fabric right|thumb|400px| L-S tectonite viewed perpendicular to the plane of the S fabric thumb|Deformed conglomerate (geology)|conglomerate showing no strain in one plane (at left) and strong stretching in the other (at right) – an L-tectonite Tectonites are metamorphic or tectonically deformed rocks whose fabric reflects the history of their deformation, or rocks with fabric that clearly displays coordinated geometric features that indicate continuous solid (ductile) flow during formation. Planar foliation results from a parallel

craton tectonic superprovince in Western Australia

core of the Baltica proto-plate and consists of the Fennoscandia, Volgo-Uralia and Sarmatia crustal segments

feature in geology

Seismotectonics is the study of the relationship between the earthquakes, active tectonics and individual faults of a region. It seeks to understand which faults are responsible for seismic activity in an area by analysing a combination of regional tectonics, recent instrumentally recorded events, accounts of historical earthquakes and geomorphological evidence. This information can then be used to quantify the seismic hazard of an area.

thumb|Slickenlines at 500m depth in a Permian sandstone In geology, a slickenside is a smoothly polished surface caused by frictional movement between rocks along a fault. This surface is typically striated with linear features, called slickenlines, in the direction of movement.