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Deform & Mount Build
| Term | Definition |
|---|---|
| Deformation | Changes in the shape and volume of rock as a result of dynamic forces within the Earth. |
| Deformation occurs during: | Pluton Emplacement Volcanism Metamorphism Continental accretion |
| Evidence of Deformation: | Seismic Activity Volcanism Plate Movement Mountain evolution |
| Deformation occur where: | Convergent, Divergent, and Transform boundaries |
| Stress | Force applied to a given area (usually expressed as kilograms per square centimeter) |
| Strain | The resulting modification of a substance as a result of applied stress (unitless - length difference/time) |
| Compression | Stress resulting from objects being pulled squeezed together; shortening of objects |
| Tension | Stress resulting from objects being pulled apart; Lengthening and thinking of objects |
| Shear | Stress resulting form forces acting parallel to one another; displacement of objects |
| Tension | Stress resulting from objects being pulled apart; Lengthening and thinking of objects |
| Elastic Strain | A deformed substance returns to its original state once stress is removed |
| Plastic Strain | Folding or fracturing of rocks as a result of applied stress, where substances behave as ductile or brittle materials |
| Factors that determine strain: | Type of strain Pressure & Temperature Rock composition Duration of stress |
| Principle of Original Horizontality | Nicholas Steno; Sediments accumulate in horizontal or nearly horizontal layers |
| Strike | the direction of a line formed by the intersection of a horizontal plane and an inclined plane |
| Dip | the measure of an inclined plane’s deviation from the horizontal, which is measured at right angles to strike direction; maxiumum angle of an inclined plane |
| Anticlines | an up-arched or convex upward fold with the oldest rock layers in its core; on either side of the crest, layers dip away from the middle - looks like an A |
| Synclines | Downward arching folds with a "U"shape; the limbs on either side dip towards the crest; the youngest layers in the core |
| Anticlines/Synclines | Form together from a compressional stress deforming layers in a ductile manner in the Earth |
| Upright Folds | the axial plane is vertical and both fold limbs dip at the same angle; appear as linear series of repeating beds in map view |
| Plunging Folds | fold axis is not vertical, but is inclined and appears to dip beneath adjacent rocks |
| Domes and Basins | appear as concentric structures that warp either upward or downward; domes are older in the middle, basins are younger in the middle |
| Boudinage Folds | "Sausage" looking folds generated by tensional stress deforming materials in a ductile nature; a series of either connected or unconnected necks |
| Geological Structures: Brittle | When rocks are exposed to stress at shallow depths, they are subjected to brittle deformation |
| Joints | Linear fractures along which no movement has taken place; almost all near-surface rocks have joints, which usually correlate with regional geologic structures |
| Faults | Rocks are considered faulted when they undergo brittle deformation and there is relative movement of the rocks on either side of the fracture plane; classified based on the relative movement of the hanging wall |
| Dip Slip Faults | Relative movement is in the direction of dip |
| Normal Fault | The hanging wall moves down relative tot eh foot wall, the rocks move with gravity (Tensional) |
| Reverse Fault | The hanging wall moves up relative to the foot wall, the rocks moves against gravity (Compressional) |
| Thrust Fault | Subset of reverse fault where the angle of the fault plane is less than 45 degrees |
| Strike-Slip Fault | Blocks on opposite sides of the fault side past each other; synonymous with transform faults in spreading zones |
| Right-lateral Strike-Slip Fault | Plate on opposite side of the fault moves to the right |
| Left-Lateral Strike-Slip Fault | Plate opposite side of the fault moves to the left |
| Oblique-Slip Fault | Contains components of Dip-Slip and Strike-slip |
| Tensional Stress | Ductile Strain: Boudinage Brittle Strain: Normal Faults |
| Compressional Stress | Ductile Strain: Anticlines/synclines Brittle Strain: Reverse/Thrust Faults |
| Shear Stress | Ductile Strain: Rotational effects (mylonitic textures) Brittle Strain: Strike-slip faults |
| Mountain | An area of land that stands significantly higher; at least 300m, than the surrounding country and has a restricted summit area; a single, isolated peak |
| Mountain Range | Linear associations of peaks and ridges |
| Mountain Systems | Complex linear zone of deformation and crustal thickening, composed of several or many mountain ranges. |
| Weathering | Differential weathering and erosion that produces topographic highs with adjacent lowlands; |
| Mesa and Butte | most are less than 300m tall and not true mountains |
| Block-Faulting (Tension stress) | Created by tectonic deformation where tension forces produce normal faults and regions down-dropped leaving topographic highs; Horst and Graben structures |
| Volcanism | Accretion of topographic highs by the continued eruption and crystrallization of magma; Volcanoes, mid-ocean ridges, etc. |
| Orogeny | Mountain building that involves crustal thickening; most occur along convergent boundaries where one plate is subducted beneath another or where two continents collide. |
| Accompaniment and Formations of Oroginies | Emplacement of batholiths, metamorphism, and thickening of the Earth's crust; sedimentary rocks that formed in marine environments are often found emplaced high in mountains as a result of orogeny |
| Oceanic-Oceanic Plate Orogeny | Characterized by deformation, igenous activity, and volcanic island arcs; accretionary wedges develop as sediments are folded and thrust over plates; 2 parallel organic belts develop, which eventually converge |
| Oceanic-Continental Plate Orogeny | Subduction of oceanic lithosphere along an oceanic-continental plate boundary; characterized by deformation, plutonism and volcanism |
| Continental-Continental Plate Orogeny | Collision of two continental plates; characterized by deformation, plutonism, volcanism, intense crustal thickening, thrusting and uplift |
| Isostacy via buoyancy | An object that has an average density less than the material in which it resides will float |
| Archimedes Principle | The object will displace an amount of that material equal to the weight of the object |
| Post Glacial Rebound | Glacial depressions shallow as a result of glacial melt |
| Glacial Maxiumum | 20,000 years ago; ice was as thick as 3km covered areas and depressed the land |
| Crust | Less dense than the mantle, floats upon the mantle |
Created by:
FaithRaquel2015
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