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Some comments

Some comments. Vertical exaggeration. On all the profiles you ’ ve drawn the vertical and horizontal scales are not the same Whelan Cove – Canning: vertical scale is 1:5000, horizontal scale is 1:50 000 This is ten times vertical exaggeration. This:. …should be this. This….

marcia-anderson
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Some comments

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  1. Some comments

  2. Vertical exaggeration • On all the profiles you’ve drawn the vertical and horizontal scales are not the same • Whelan Cove – Canning: vertical scale is 1:5000, horizontal scale is 1:50 000 • This is ten times vertical exaggeration

  3. This: …should be this.

  4. This… …should be this.

  5. And this… …should be this.

  6. Much easier to compare the shape of these two than…

  7. … these two, even though here their vertical scales are identical.

  8. Calculating vertical exaggeration • Vertical exaggeration (VE) is the vertical scale divided by the horizontal scale • Remember that scales are ratios to begin with • If vertical scale is 1:5000 and horizontal scale is 1:50000 the VE is = (1/5000)/(1/50000) = 50000/5000 = 10 • If vertical scale is 1:20000 and horizontal scale is 1:50000 the VE is = (1/20000)/(1/50000) = 50000/20000 = 2.5

  9. Structure Lab

  10. Rule of Vs (vees) • Helps in reading geological maps • As a contact changes elevation, when viewed from overhead (map view), it shifts in the direction of dip i.e., a contact “vees” in the direction of dip

  11. Rule of Vs • Shallowly dipping contacts make “large” Vs • Horizontal contacts run parallel to the topographic contours • Steeply dipping contacts make “small” Vs • Vertical contacts run straight across topographic contours

  12. Shallowly dipping contacts

  13. Shallowly dipping contacts

  14. Horizontal contacts

  15. Horizontal contacts

  16. Steeply dipping contacts

  17. Steeply dipping contacts

  18. Vertical contacts

  19. Vertical contacts

  20. Steep dip (small “vees”) Horizontal (parallel to contours) Vertical dip (runs straight across topo) Shallow dip (big “vees”)

  21. Question 1what is the value of the contours?

  22. Question 1position the contours

  23. Question 1draw the surface

  24. Question 1where do the contacts cut the surface?

  25. Question 1what is the orientation of the contacts? Hotizontal!!!(contacts follow contours)

  26. Question 1fill the units

  27. Question 1finished!At least part (a)

  28. Question 2a3 is younger than 2 is younger than 1

  29. Question 2atherefore 3 is above 2

  30. Question 2aand 2 is above 1

  31. Question 2awithout any specific dip data, draw lines to separate the units

  32. Question 2aseparate 3 from 2

  33. Question 2aseparate 2 from 1Finished!

  34. Question 2blet’s just focus on the boundary between layers 2 and 3

  35. Question 2bwhat is the dip of the boundaries?

  36. Question 2b“v” indicates dip to the right

  37. Question 2bdraw a dipping contact

  38. Question 2bno “v” indicates that the contact is vertical

  39. Question 2bdraw a vertical contact

  40. Question 2bcomplete the line…and draw the others in the same way!

  41. A couple of points… • Rock units are assumed to be planar and of equal thickness throughout the area • Wider outcrop in one place and narrower outcrop in another indicates differences in dip • When drawing sections try to maintain thickness of units around folds.

  42. Contacts are parallel and units maintain thickness

  43. Block diagrams… • See if you can work these ones out for yourself • But ask questions • Hint: look at the strike and dip symbols.

  44. Dykes and faults • This exercise is fairly intuitive • Note: we cannot tell the absolute sense of motion on a fault thus we indicate relative motion with two “half” arrows

  45. Strike and dip Put strike FIRST (up to 3 digits) Then DIP (only 2 digits) Then DIP direction / NE 110 25

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