Crustal Deformation

• The core of the Earth is divided into an outer core of liquid nickel and iron and an inner core of solid nickel and iron.
• The mantle is the thickest layer of the Earth, divided into an upper and lower mantle, composed of hot dense semisolid rock, and convection of heat occurs in the asthenosphere.
• The crust is the thinnest and topmost layer of the Earth, composed of large chunks of land mass called tectonic plates.
• Stress is a force per unit area that is placed on a rock, and there are three types of stresses: compression, tension, and shearing.
• Compression is a force that squeezes rocks together, causing rocks to fold or fracture (break).
• Tension is a force that lengthens or breaks rocks apart.
• Shearing is a force that makes rock slide along each other.
• Elastic deformation is recoverable, involves small amounts of strain, and doesn’t happen to rocks.
• Plastic deformation is permanent, involves large amounts of strain, and happens to rocks as movement occurs along small structural defects.
• Fracture, also known as brittle deformation, is a rupture where the rock moves in opposite directions on either side of a break.
• A fault is a large crack in the earth’s crust where one part of the crust has moved against each other, usually occurs in plate boundaries, and the surface trace of a fault is called a fault line.
• Normal faults are created by the tension, occur when two blocks of plates move apart, and occur in divergent plates.
• Reverse faults are created by compression, occur when two blocks of plates are pushed towards and against each other, and occur in convergent plates.
• Folding may result in extremely complex geometries.
• Crustal structures include folds, which are formed during crustal deformation when rocks are bent into a series of wave-like undulations.
• Orogenic settings produce large volumes of folded rock.
• You may watch the video of the following link: https://www.youtube.com/watch?v=0VKE d5Z2FSg.
• In a fold, the limbs refer to the two sides of the fold, the axis or hinge is a line drawn down the points of maximum curvature of each layer, the axial plane is an imaginary surface that divides a fold symmetrically, and plunge is the angle at which the axis is inclined in complex folding.
• Dome is an upwarped displacement of rocks, and basin is a downwarped displacement of rocks.
• Most folds result from compressional stresses which shorten and thicken the crust.
• Folds often occur in a series.
• Deformed rock often experiences multiple events.
• Common types of folds include anticline, syncline, monocline, dome, and basin.
• Anticline is an upfolded or arched rock layers, syncline is a downfold or trough of rock layers, and monocline is a large, step-like fold in otherwise horizontal sedimentary strata.
• Folds can be classified into anticlines, synclines, domes, and basins.
• Strike-slip faults are created by shearing, involve two pieces of plates moving by sliding along each other, occur in transverse plate boundaries, and are mostly associated with earthquakes due to friction.
• Graben fault is a fault produced when tensional stresses result in the subsidence of a block of rock, and on a large scale these features are known as rift valleys.
• Horst fault is the development of two reverse faults causing a block of rock to be pushed up.
• Fault-block mountains are mountains formed by the movement of faults.