Geol Outline 4

Geol Outline 4 - 1 Faulting Folding and Mountain Building a...

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1. Faulting, Folding, and Mountain Building a. Orogenesis a.i. Forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates a.ii. Causes a.ii.1. Continental collisions a.ii.1.a. Oceanic lithosphere can completely subduct a.ii.1.a.i. Closes pre-existing ocean basin a.ii.1.a.ii. Brings 2 continental crust blocks together a.ii.1.b. Buoyant continental crust will not subduct a.ii.2. Continent-on-continent collision a.ii.2.a. Creates broad welt of crustal thickening a.ii.2.a.i. Due to thrust faulting and flow folding a.ii.2.a.ii. Center of belt consists of high-grade metamorphic rocks a.ii.2.b. Fold and thrust belts extend outward on either side a.ii.3. Continental rifting a.ii.3.a. Continental crust is uplifted in rift settings a.ii.3.a.i. Thinned crust; mantle responds isostatically a.ii.3.a.ii. Decompressional melting adds asthenospheric magma a.ii.3.a.iii. Increased heat flow from magma expands and uplifts rocks a.ii.3.a.iv. Rifting creates linear fault block mountains and linear basins b. Deformation b.i. Ductile b.i.1. Rocks deform by flood and flowing b.i.2. Occurs in DEEPER crust b.ii. Brittle b.ii.1. Rock breaks by fracturing (jointing/faulting) b.ii.2. Occurs in SHALLOW crust b.iii. Factors that control b.iii.1. Temperature b.iii.1.a. Hot rocks are more ductile than cool rocks b.iii.2. Pressure b.iii.2.a. Rocks under high pressure are more ductile than those at low pressure b.iii.3. Deformation rate b.iii.3.a. Sudden changes produce brittle behavior, while gradual changes encourage ductile behavior b.iii.4. Rock type b.iii.4.a. Some rocks have a proclivity to behave ductilely b.iv. Stress vs. Strain
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Stress b.iv.1.a. A measure of the amount of force applied over a given area b.iv.1.b. 3 types b.iv.1.b.i. Compression b.iv.1.b.ii. Tension b.iv.1.b.iii. Shear b.iv.1.b.iii.1. Sliding past one another, often results in faulting c. Folds, Faults, and Joints c.i. Folds c.i.1. Layered rocks deformed into curves c.i.2. Terminology c.i.2.a. Hinge c.i.2.a.i. Portion of maximum curvature on a fold c.i.2.b. Limb c.i.2.b.i. Less curves sides of a fold c.i.2.c. Axial plane c.i.2.c.i. Imaginary surface defined by connecting hinges of successively nested folds c.i.3. 3 types c.i.3.a. Anticline c.i.3.a.i. Arch-like fold, limbs dip away from the hinge c.i.3.b. Syncline c.i.3.b.i. Trough-like fold; limbs dip toward the hinge c.i.3.c. Monocline c.i.3.c.i. Fold like a carpet draped over a stairstep c.ii. Faults c.ii.1. Planar fractures offset by movement across the break c.ii.2. Types c.ii.2.a. Normal fault- tension/divergent boundary c.ii.2.a.i. Footwall UP, hanging wall DOWN c.ii.2.b. Thrust Fault- compression/convergent boundary c.ii.2.b.i. Footwall DOWN, hanging wall UP c.ii.2.b.ii. Reverse fault at HIGH angle, thrust fault at LOW angle c.ii.2.b.iii. Brings old rocks over younger rocks c.ii.2.c. Strike Slip Faults- shear/transform boundary c.ii.2.c.i. Plate ACROSS moving left relative to you,
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This document was uploaded on 10/28/2011 for the course GEOL 101 at UNC.

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Geol Outline 4 - 1 Faulting Folding and Mountain Building a...

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