glg310 structural geology. 21 december 2015glg310 structural geology

GLG310 Structural Geology

April 21, 2023 GLG310 Structural Geology

GLG310 Structural Geology

d is differential stress

-Engelder, 1993, Stress regimes in the lithosphere, Princeton Univ. Press

April 21, 2023 GLG510 Advanced Structural Geology

Rheology: “science of deformation and flow

of matter”or

relationship between stress and strain

Idealized Elastic MaterialLinear 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

April 21, 2023 GLG510 Advanced Structural Geology

E (young’s modulus) = d a/d ea Units of stress

-Pollard and Fletcher, 2005

April 21, 2023 GLG310 Structural Geology

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

April 21, 2023 GLG510 Advanced Structural Geology

a = f/A ea = (b-B)/B

p = 0 ep = (w-W)/W

= - ep / ea

(Poisson ratio)Measures compressibility

Axial versus transverse

deformation

Idealized Elastic Material

April 21, 2023 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/rheology/inelastic.htm

Plasticity• Steady deformation at yield strength

Plasticity• Steady deformation at yield strength

April 21, 2023 GLG510 Advanced Structural Geology

Viscosity• Strain rate proportional to differential stress

April 21, 2023 GLG310 Structural Geology

April 21, 2023 GLG310 Structural Geology

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

Variations in mechanical behavior

April 21, 2023 GLG310 Structural Geology

Rock deformation experiments

April 21, 2023 GLG310 Structural Geology

GLG310 Structural Geology

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

April 21, 2023 GLG310 Structural Geology

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

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

Rocks can flow: salt ascends through overlying sediments because it is bouyant

April 21, 2023 GLG310 Structural Geology