1. Geologic Wonders of Central Texas Produced by and for the Outreach Lecture Series of the Environmental Science Institute. We request that the use of any of these materials include an acknowledgement of Dr. Leon E. Long and the Outreach Lecture Series of the Environmental Science Institute of the University of Texas at Austin. We hope you find these materials educational and enjoyable. by Dr. Leon E. Long Outreach Lecture Series Volume 17

2. Geologic Wonders Of Central Texas Geologic Wonders Of Central Texas Department of Geological Sciences Dr. Leon E. Long

3. image 1 - Two divisions of Texas along an S-shape line that passes through Austin

4. image 2 - Texas average annual rainfall; climatic impact on the landscape

5. image 3 - Geologic map of Texas

6. image 4 - North Central sub- province North-Central Texas Austin

7. image 5 - Gulf Coastal Plain sub- province Gulf Coastal Plain Austin

8. image 6 - Trans-Pecos sub- province Trans-Pecos Austin

9. image 7 - High Plains sub- province Austin

10. image 8 - Edwards Plateau sub- province Austin

11. image 9 - Cretaceous interior Seaway

12. image 10 - Llano Uplift sub- province Austin

13. image 11 - Orientation map showing Austin astride (or near to) three sub-provinces

14. image 12 - Llano Uplift basement geology

15. image 13 - Geologic timescale; ages of formation of rocks in the Llano Uplift

16. image 14 - Inverse geologic timescale; ages of erosion or non- deposition in the Llano Uplift

17. image 15 - Orientation; Enchanted Rock batholith within the Llano Uplift

18. image 16 - Oblique aerial photo of Enchanted Rock

19. image 17 - Major minerals in granite

20. image 18 - Igneous intrusive origin of granite

21. image 19 - Photo from top of Enchanted Rock showing adjacent exfoliation dome

22. image 20 - Photo of exfoliation sheets popping off exfoliation sheet

23. image 21a - Photo of joints in granite; joints v. faults

24. image 21b - Photo of joints with labels

25. image 22 - Weathering attack of granite

26. image 23 - Photo of rounded granite boulder

27. image 24 - Vertical aerial photo of rounded exfoliation domes at enchanted rock

28. image 25a - Photo of view to the south; Cretaceous escarpment; rate of weathering of granite

29. image 25b - View to the south with labels

30. image 26a - Photo of view to the east; Riley Mountains

31. image 26b - View to the east with labels

32. image 27 - Ages of rocks symbolized in the preceding image

33. image 28 - Geologic map of Enchanted Rock and vicinity

34. image 29 - Map showing all 3 types of geologic contac: depositional (Cretaceous escarpment), fault (Riley Mountains), and igneous intrusive (Enchanted Rock batholith)

35. image 30 - Stage I of landscape development (form the rocks)

36. image 31 - Stage II (deform the rocks) and Stage III (erode the rocks); inversion of topography

37. Image 32a - Fault drag at Hoover Point

38. Image 32b - Fault drag at Hoover Point with text

39. Image 33 - Fault Zone

40. image 34 - Geologic map showing Sandy Creek

41. image 35 - Landscape development I

42. image 36 - Landscape development II

43. image 37 - Landscape development III

44. image 38 - Landscape development IV

45. image 39 - Landscape development V

46. Image 40 - Braided stream vs. meandering stream

47. image 41 - Granite weathering into grus

48. Image 42 –Granite grus

49. Image 43 – Sandy Creek

50. Image 44 – Orientation map of Austin and vicinity

51. image 45 – Bedrock in Austin on two sides of Mt. Bonnell Fault

52. Image 46 - Photo of Pilot Knob

53. image 47 - Pilot Knob volcano

54. Image – Photograph of modern volcano erupting

55. image 48 - Pilot Knob then and now

56. Image 49 – McKinney Falls

57. Image 50 – Close-up of falls

58. Image 51 – Layer cake stratigraphy

59. Image 52 – Ordinary rock?

60. Image 53 – Fossil of an ammonite!

61. image 54 - Ammonite

62. Image 55 - Development of stream terraces

63. Image 56 - Topographic contour map, McKinney Falls State Park

64. Image 57 -Stream terrace deposits, McKinney Falls State Park

65. Image 58 - Recent floodplains, Austin and vicinity

66. Image 59 - Older terraces

67. Image 60 - Even older terraces

68. Image 61 - Highest, most ancient stream terraces

69. Image 62 - Austin airports on terraces

70. Image 63 - View from Mt. Bonnell

71. Image 64 - Stair step topography

72. Image 65 - Desiccation cracks

73. Image 66 -Texas Valley Country

74. Image 67 - Long profile of stream

75. Image 68 - Fossil and active meanders

76. Dr. Leon Long Professor and The Second Mr. and Mrs. Charles E. Yager Professorship and member of the Academy of Distinguished Teachers Dr. Leon Long is a geology professor at the University of Texas at Austin whose research interests include isotope geology, especially to use naturally occurring radioactivity and its daughter products as a geologic clock, and as a geochemical tracer. He is also interested in applying the Rb- Sr isotopic age method to clay minerals with a possibility of dating when weathering had produced an ancient soil zone. As the department’s generalist, Dr. Long has also written the textbook for the introductory course.