1. Outline Deformation Strain Displacement Vectors Strain ellipse Linear strain Shear strain Quantifying strain

2. Kinematic Analysis The study of the movements of rock during deformation Examples: –Pepperoni moves from point A to point B –A feldspar grain goes from square to elliptical –Pacific plate moves relative to NAM

3. What is Deformation?

4. What causes deformation? Forces that exceed the strength of a rock

5. What are the possible sources of these forces?

6. Deformation vs. Strain Strain: changes in shape and/or volume

9. Rigid Body Deformation Particles in a body do not change relative positions Translations Rotations

10. Rigid Body Translation Define frame of reference Y X Yo+n Xo+mXo Yom n Displacement vector

11. All Plate Motions are Rotations Motion with respect to what? v= w r i sin 

12. Vectors Displacement vectors –Direction of movement –Distance

13. Vectors showing extension from dike intrusion

14. Homogeneous vs. Heterogeneous Strain Homogeneous strain is easy to measure Circles become ellipses Squares become parallelograms

15. Strain Ellipse helps visualize strain in rocks Undeformed Deformed Principal Strain Axes: they stay perpendicular

16. Principal Strain Axes 2D: X>Y 3D: X>Y>Z

17. FINITE STRAIN INCREMENTAL STRAIN

18. Extension Quadrant Shortening Quadrant No change in length

19. Coaxial Strain: principal axes do not rotate Simple Shear

20. Non-Coaxial Strain: principal axes rotate Pure Shear

21. Simple vs. Pure Shear Simple Shear Pure Shear

22. Quantifying Strain

23. Linear Strain Measures relative changes in length EXTENSION (e) = ( L f -L o )/ L o

26. Shear Strain Measures changes in angles of initially perpendicular lines Shear angle (  ) increases with increasing strain Shear strain (  )= tan 

29. Measuring Strain Need objects with a known original shape Spheres Circles Lines