GLG310 Structural Geology - Arizona State...

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GLG310 Structural Geology

10 October 2013 GLG310 Structural Geology

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GLG310 Structural Geology

sd is differential

stress

-Engelder, 1993,

Stress regimes in

the lithosphere,

Princeton Univ.

Press

10 October 2013 GLG510 Advanced Structural Geology

Rheology:

“science of deformation and flow

of matter”

or

relationship between stress and

strain

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Idealized Elastic Material Linear relationship

between force and

extension (Hooke,

1676):

• Ut tensio sic uis

• As extension so the

force

• Analogous to spring

constant

http://www.see.leeds.ac.uk/structure

/rheology/hooke.htm

GLG310 Structural Geology

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10 October 2013 GLG510 Advanced Structural Geology

E (young’s modulus)

= d sa/d ea

Units of stress

-Pollard and Fletcher, 2005

10 October 2013 GLG310 Structural Geology

http://silver.neep.wisc.edu/~lakes/PoissonIntro.html

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10 October 2013 GLG510 Advanced Structural Geology

sa = f/A

ea = (b-B)/B

sp = 0

ep = (w-W)/W

n = - ep / ea

(Poisson ratio)

Measures

compressibility

Axial versus

transverse

deformation

Idealized Elastic Material

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10 October 2013 GLG510 Advanced Structural Geology

Stiffness and strength “Lest there be any possible, probably, shadow of

doubt, strength is not, repeat not, the same thing as stiffness. Stiffness, or Young’s modulus or E, is concerned with how stiff, flexible, springy or floppy a material is. Strength is the force or stress needed to break a thing. A biscuit is stiff but weak, steel is stiff and strong, nylon is flexible (low E and strong), raspberry jelly is flexible (low E) and weak. The two properties together describe a solid about as well as you can reasonably expect two figures to do.”

(Gordon, New science of strong materials, 2006)

http://www.see.leeds.ac.uk/structure/rhe

ology/inelastic.htm

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Plasticity • Steady deformation at yield strength

Plasticity • Steady deformation at yield strength

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10 October 2013 GLG510 Advanced Structural Geology

Viscosity • Strain rate proportional to differential stress

10 October 2013 GLG310 Structural Geology

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10 October 2013 GLG310 Structural Geology

http://www.youtube.com/watch?v=GxdfoJoWNE4

Variations in mechanical behavior

10 October 2013 GLG310 Structural Geology

Rock deformation experiments

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10 October 2013 GLG310 Structural Geology

GLG310 Structural Geology

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http://www.cast.com.sg/s_soil.html

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10 October 2013 GLG310 Structural Geology

http://www.youtube.com/watch?v=n4ZAb-p-dIw

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http://maydamedia.com/Images/Chapter11/Chart11.1.jpg

Rocks can flow: salt ascends

through overlying sediments

because it is bouyant

10 October 2013 GLG310 Structural Geology