AN INVESTIGATION OF THE ORIGIN OF ROCK CITY AND CAUSE OF PIPING PROBLEMS AT MOUNTAIN LAKE, GILES COUNTY, VIRGINIA A thesis submitted To Kent State University in partial fulfillment of the requirements for the degree of Master of Science by Nidal Walid Atallah December, 2013 Thesis written by Nidal Walid Atallah B.S., Earlham College, 2009 M.S., Kent State University, 2013 Approved by ___________________________________ Abdul Shakoor, Ph.D., Advisor ___________________________________ Daniel Holm, Ph.D., Chair, Department of Psychology ___________________________________ Janis Crowther, Associate Dean, College of Arts and Sciences TABLE OF CONTENTS Page ACKNOWLEDGMENT ................................................................................................................ vii ABSTRACT ..................................................................................................................................... 1 CHAPTER 1: INTRODUCTION .................................................................................................... 3 1.1 Overview ................................................................................................................................ 3 1.2 Historical and Cultural Significance of Mountain Lake ........................................................ 4 1.3 Hydrologic and Geomorphic Settings of the Study Area ....................................................... 8 1.4 Geologic Setting of the Study Area ....................................................................................... 9 1.5 Review of Previous Hypotheses on the Origin of Mountain Lake and Rock City .............. 14 1.6 Water-Level Fluctuations at Mountain Lake ....................................................................... 20 1.6.1 Past Episodes of Water-level Drops as Documented by Previous Studies ................... 20 1.6.2 Hypotheses on Mountain Lake’s Water-level Fluctuations .......................................... 25 CHAPTER 2: METHODOLOGY ................................................................................................. 31 2.1 Investigations of Rock City ................................................................................................. 31 2.1.1 Analysis of the Outcrop Scarp Complex ....................................................................... 32 2.1.2 Mapping of Rock City .................................................................................................. 32 2.1.2 Discontinuity Measurements and Stereonet Analysis ................................................... 33 2.2 Investigations of the Piping Potential of Lake-bottom Sediment ........................................ 36 2.2.1 Sample Collection ......................................................................................................... 36 2.2.2 Laboratory Investigations ............................................................................................. 39 CHAPTER 3: ROCK CITY: MAPPING, ORIGIN, AND MODE OF DISPLACEMENT .......... 48 3.1 Introduction .......................................................................................................................... 48 3.2 Results for the Outcrop Scarp Complex .............................................................................. 48 3.3 Analysis of Discontinuity Orientation Data ......................................................................... 53 3.3.1 Description of the Overall Debris Field ........................................................................ 53 3.3.2 Bedding-Plane Orientations of Rock Blocks in Rock City ........................................... 59 3.3.3 Joint Orientations within Rock Blocks in Rock City .................................................... 63 3.4 Discussion and Interpretations ............................................................................................. 66 ii 3.4.1 Interpretation of the Outcrop Scarp Complex ............................................................... 66 3.4.2 Comparison of Discontinuity Orientations between the Rock Blocks and Scarp Outcrops ................................................................................................................................. 68 3.4.3 The Origins of Rock City and Mountain Lake ............................................................. 71 CHAPTER 4: EVALUATION OF PIPING SUSCEPTIBILITY OF LAKE-BOTTOM SEDIMENT ................................................................................................................................... 76 4.1 Data Presentation ................................................................................................................. 76 4.1.1 Grain Size Distribution and Atterberg Limits ............................................................... 76 4.1.2 Density and Compaction-mold Permeameter Test Data ............................................... 83 4.2 Discussion and Interpretations ............................................................................................. 91 4.2.1 Discussion of Limitations ............................................................................................. 91 4.2.2 The Role of Piping in Lake-level Fluctuations ............................................................. 92 CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS ................................................. 96 5.1 Conclusions .......................................................................................................................... 96 5.2 Recommendations ................................................................................................................ 97 REFERENCES .............................................................................................................................. 99 APPENDIX A .............................................................................................................................. 104 APPENDIX B .............................................................................................................................. 107 APPENDIX C .............................................................................................................................. 116 APPENDIX D .............................................................................................................................. 125 iii LIST OF FIGURES Figure 1.1: Location of the study area ............................................................................................. 5 Figure 1.2: Geologic map of the study area .................................................................................... 5 Figure 1.3: Mountain Lake Lodge with main sandstone structure in the middle ............................. 7 Figure 1.4: Mountain Lake when full in 2005 ................................................................................. 7 Figure 1.5: Location of Mountain Lake within USGS hydrologic units ....................................... 10 Figure 1.6: Topographic Map showing stream flow directions around Mountain Lake ................ 10 Figure 1.7: Block Diagram of Mountain Lake and its vicinity ...................................................... 11 Figure 1.8: SE-NW regional lineation ........................................................................................... 19 Figure 1.9: Seismic refraction line and profile at the northern end of lake .................................... 21 Figure 1.10: Aerial images of Mountain Lake at different water levels ........................................ 22 Figure 1.11: Drastic water level drop in December, 2012 ............................................................. 22 Figure 1.12 The locations of lake-bed depressions ........................................................................ 23 Figure 1.13: Examples of piping holes within the depressions ...................................................... 24 Figure 1.14: Lake-bed bathymetric map ........................................................................................ 28 Figure 1.15: Footage of lake-bottom piping holes during scuba diving missions in June, 2012 ... 28 . Figure 2.1: An example of the two principal joint sets along a rock block in Rock City representing the orientations of its sides. ....................................................................................... 34 Figure 2.2: Soil sample locations. .................................................................................................. 37 Figure 2.3: Hydrometer test apparatus. .......................................................................................... 43 Figure 2.4: Casagrande’s plasticity chart. ...................................................................................... 43 Figure 2.5: Shelby tube sampling. ................................................................................................. 45 Figure 2.6: Apparatus set-up for the compaction-mold permeameter test. .................................... 45 Figure 3.1: Rock City Map ............................................................................................................ 49 Figure 3.2: An oblique 3D view and east-facing photo of Mountain Lake, Pond Drain, and Rock City................................................................................................................................................. 50 Figure 3.3: Examples of scarp outcrops ........................................................................................