4 TELLING TIME GEOLOGICALLY GEOLOGIC TIME SCALEOrganizes all of Earth history into blocks of timeutilizing significant geologic events.Preliminary subdivisions were done in the 18th and19th centuries using relative dating techniques.20th century allowed determination of numerical ages.Used all the numerical dating techniques to do this.
5 TELLING TIME GEOLOGICALLY GEOLOGIC TIMESCALESubdivisions of TimeEonsErasPeriodsEpochsNone last equal intervals oftime.Based on events.
6 FOLDS, FAULTS & MOUNTAIN BELTS Mountains and earthquakes illustrate the energy andpower of plate tectonics.Produces large mountain ranges such as the Rockies,Alps, Himalaya and Appalachians.We also observe rocks that have been bent or folded.Focus on the geologic processes that deform theEarth’s crust = STRUCTURAL GEOLOGY.
7 FOLDS, FAULTS & MOUNTAIN BELTS Mt. EverestLong’s Peak, CO
8 FOLDS, FAULTS & MOUNTAIN BELTS STRESSING AND STRAINING ROCKSPlate movement applies powerful forces to rocks.Converging, diverging and sliding rocks subject theirmargins to powerful stresses.STRESS is the force applied to a rock.If rocks are stressed enough, they will DEFORM.DEFORMATION alters the shape and/or volume ofthe rocks.This change is called STRAIN.
9 FOLDS, FAULTS & MOUNTAIN BELTS STRESSING AND STRAINING ROCKSRocks can be stressed in three ways.1. TENSIONAL STRESSOccurs at divergent plate boundaries.Thins crust vertically and lengthens crust laterally.
10 FOLDS, FAULTS & MOUNTAIN BELTS STRESSING AND STRAINING ROCKS2. COMPRESSIONAL STRESSOccurs at convergent plate boundaries.Crumples rock, thickens rock vertically andshortens rock laterally.
11 FOLDS, FAULTS & MOUNTAIN BELTS FOLDS, FAULTS & MOUNTAIN BELTS STRESSING AND STRAINING ROCKS3. SHEAR STRESSOccurs at transform boundaries.Rocks forced past each other in parallel, butopposite directions.
12 FOLDS, FAULTS & MOUNTAIN BELTS TYPES OF DEFORMATIONELASTIC DEFORMATIONSTRESS is applied, released and rock returns tooriginal shape and volume.Material is not DEFORMED.If stressed to a point where the material doesn’t resumeoriginal shape and volume, the rock is deformed.Point at which this occurs is the ELASTIC LIMIT.Pressure and temperature when stress is applied alsodetermine how rocks deform at the elastic limit.
13 FOLDS, FAULTS & MOUNTAIN BELTS TYPES OF DEFORMATIONELASTIC DEFORMATIONRocks subjected to stress at LOW temperature andLOW pressure tend to BREAK.Causes the bonds between atoms to break.Breaking in rocks is called BRITTLE FAILURE.
14 FOLDS, FAULTS & MOUNTAIN BELTS TYPES OF DEFORMATIONPLASTIC or DUCTILE DEFORMATIONRocks subjected to stress at HIGH temperature andHIGH pressure tend to BEND, resulting fromPLASTIC or DUCTILE DEFORMATION.An irreversible change in shape and/or volume occurswithout the rock breaking.Rocks go beyond the elastic limit.Atoms move about and adjust without the bondsbreaking.Atoms move from areas of high stress to those withlow stress.
15 FOLDS, FAULTS & MOUNTAIN BELTS TYPES OF DEFORMATION
16 FOLDS, FAULTS & MOUNTAIN BELTS FACTORS AFFECTING ROCK DEFORMATION1. HeatWeakens bonds within minerals.2. TimeWith enough time plastic deformation occurs.Rapid stress causes breakage.3. CompositionMineralogy of rocks affect how rocks respond tostress (calcite, mica weak; garnet, qtz strong).Water is another compositional factor.Increased H2O content > plastic deformation
17 FOLDS, FAULTS & MOUNTAIN BELTS Rocks bend and flow when deformed plastically.Produces FOLDS.FOLDS are typically associated with compression.FOLDS are found in metamorphic rocks and wet, clay-rich sedimentary rocks and sediments at or nearthe Earth’s surface.
18 FOLDS, FAULTS & MOUNTAIN BELTS ANTICLINES AND SYNCLINESAn ANTICLINE is an inverted bowl-shaped structure formedwhen sedimentary rock layers are folded to produce anarch or elongated dome. The stratigraphically olderrocks are located at the center of the anticline.
19 FOLDS, FAULTS & MOUNTAIN BELTS ANTICLINES AND SYNCLINESA SYNCLINE is a trough- or bowl-shaped fold in which theyoungest rock forms the core and the limbs dip towardthe axis.
20 FOLDS, FAULTS & MOUNTAIN BELTS FOLD SYMMETRYSYMMETRICAL FOLDSTo be symmetrical, the limbs of the fold must dip atthe same angle away from the fold axis.
21 FOLDS, FAULTS & MOUNTAIN BELTS FOLD SYMMETRYASYMMETIRCAL FOLDSTo be asymmetrical, the limbs of the fold must dip atthe different angles away from the fold axis.
22 FOLDS, FAULTS & MOUNTAIN BELTS FOLD SYMMETRYIf the limbs of a fold are rotated past vertical, anOVERTURNED FOLD exists.
23 FOLDS, FAULTS & MOUNTAIN BELTS FOLD SYMMETRYIf the axial plane tilts to near horizontal or horizontally,a RECUMBENT FOLD exists.
24 FOLDS, FAULTS & MOUNTAIN BELTS FOLD SYMMETRYIf the axis of the fold is tilted beyond horizontal, aPLUNGING FOLD exists.
25 FOLDS, FAULTS & MOUNTAIN BELTS DOMES AND BASINSA DOME is a doubly plunging anticline.
26 FOLDS, FAULTS & MOUNTAIN BELTS DOMES AND BASINSA BASIN is a doubly plunging syncline.
27 FOLDS, FAULTS & MOUNTAIN BELTS Rocks are brittle at low temperatures and lowlithostatic pressures.Some stresses from tectonic forces break rocks.Brittle failure is observed in rocks as FRACTURES.Rocks with fractures along which there is no movementare called JOINTS.Fractures along which movement has occurred arecalled FAULTS.
29 FOLDS, FAULTS & MOUNTAIN BELTS Rock masses or FAULT BLOCKS along either side ofthe fracture have moved relative to each other.Usually there is displacement of layers on either side ofthe fault.
30 FOLDS, FAULTS & MOUNTAIN BELTS Faults may look like lines on a rock surface, butactually represent planes.Called FAULT PLANE.
31 FOLDS, FAULTS & MOUNTAIN BELTS TYPES OF FAULTSAll faults result from motion between adjacent blocks.Either or both blocks SLIP, relative to their originalposition.Each type of stress (compression, tension and shear)will produce a unique type of fault.Determine what type of fault you are observing andyou will know what type of stress produced it.
32 FOLDS, FAULTS & MOUNTAIN BELTS TYPES OF FAULTSSTRIKE-SLIP FAULTSProduced by horizontal slip of adjacent blocks.Movement is parallel to the fault plane.Produced by horizontal shear stresses.Occur at transform plate boundaries.
33 FOLDS, FAULTS & MOUNTAIN BELTS TYPES OF FAULTSSTRIKE-SLIP FAULTSThe most famous strike-slip fault is the San Andreas.
34 FOLDS, FAULTS & MOUNTAIN BELTS TYPES OF FAULTSSTRIKE-SLIP FAULTSSan Andreas Fault in 1906 earthquake moved 7 m inseveral seconds.Parts creep along daily with little movement and littledamage.Others move less often, but with large displacement.Surface expression may produce long linear features,ridges or depressions.
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