A boundary between bodies with different lithologies. It can be depositional, intrusive or created by faulting. A remotely observed colour change is evidence for a candidate lithological contact, but illumination, soil and vegetation changes require independent checks.
A fracture filled by minerals precipitated from a fluid. Quartz and calcite are common examples. Growth textures and cross-cutting relations can constrain opening and fluid-flow history, but mineral filling alone does not establish whether the fracture also experienced fault slip.
A fluid-filled fracture can open perpendicular to the least compressive principal stress. In a compression-positive contact approximation, effective stress is . Opening an initially intact plane of tensile strength requiresA sufficiently weak pre-existing crack can open near zero effective compression. Increasing isotropic pore fluid pressure translates all effective principal stresses without rotating their directions, so an opening fracture and a frictional normal fault can record compatible stress axes at different pressure episodes. Subsequent mineral precipitation creates a mineral vein; white appearance alone does not identify its filling mineral.
An opening fracture in rock with little or no shear displacement across its faces. A geological joint is approximately normal to the least compressive principal stress when it forms in a homogeneous medium. It can remain open or become a mineral vein. Unlike a fault, a geological joint need not contain crushed fault rock.
Distributed permanent change of shape without requiring a discrete through-going brittle rupture. Its mechanisms and rate depend on temperature, stress, composition and timescale; deep ductile structures need not be active earthquake faults.
Reduction of distance between material markers during tectonic deformation. Folding, reverse faulting and distributed strain can accommodate it; the shortening direction alone does not determine all three principal stresses.
The relative movement direction across a shear zone, inferred from appropriately interpreted structural indicators.
Construction of elevated mountain regions through crustal thickening, magmatic addition or other tectonic processes.
An elongated region affected by mountain building, commonly containing related thrust belts, metamorphic belts and deformed sedimentary successions. Restoring its age and internal structure across separated continental blocks can test continental reconstruction.
The mountain system along western South America, associated with subduction and a spatially variable history of crustal shortening.
An increase in rock or surface elevation caused by tectonic processes; rock uplift and surface uplift can differ because of erosion.
A heterogeneous geological body containing blocks within a deformed matrix; formation can involve tectonic, sedimentary or mixed processes.
Return of formerly buried rock toward the surface through tectonic deformation, often aided by erosion.
Modification of pre-existing rocks and structures during subsequent tectonic events.
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