This lab requires you to watch the video which I have I can attach after wards.
The instructions on how to perform this lab are included in the document titled "Striationlab.pptx"
The information on the lab is in the document titled "lab05_striae.pdf"
You will need to create a rose diagram if not I have attached one for you titled "rose diagram_00.jpeg"
you will need to use the date I have attached titled "Lab5_striations_data.xls"
ERSC/GEOG 2P05 1 Striae and a comparison of striation direction Introduction: Bedrock striations are perhaps one of the best indicators of glacial erosion. These scratches indicate the local vagaries of basal ice movement that occur as a result of variations in principal stress directions and micro-topographic bed control. For too long, striae have been ignored as being of rudimentary significance and limited value. However, when time is taken to measure the typical crosscutting relationships of superimposed striae, long-axis depth variations and the presence of micro-faulting, striations can be a useful tool in deciphering ice movements, chronology and icebed conditions. Striae exhibit a wide variation in form from straight micro-grooves of a few millimetres in depth extending for only a few centimetres, to some that are almost a centimetre deep and extending for over a metre. In some cases, smaller striations occur at the base of large striations. Delicate tracery of cross-cutting striae commonly occurs on boulder and clast surfaces and, where resistant knobs occur, striae may circumvent these obstructions. Many striae have a variable depth becoming shallower in the direction of ice movement, possibly indicative that the striating tool became blunt with travel down-ice. Figure 1: Striations in limestone at the northern shore of Lake Erie (visible top to bottom aligned roughly with compass edge, finger pointing at one) ERSC/GEOG 2P05 2 Striae on individual clasts and bedrock surfaces are products of either direct scratching of clasts and boulders held in the basal ice or clasts within a moving basal debris layer. The depth, width and length of individual striations, therefore, reflect the combined influence of basal ice stress levels, ice velocity, meltwater presence, debris concentrations, effective stress levels, the sharpness of the individual clast indenter and the properties of both the indenter and the surface being scratched. In general, a striation is thought to be produced by plastic deformation of the rock surface against which the tool is applied. Often small levées are produced on either side of the main trough. In those cases where the difference in hardness between the indenter and the surface is small, a shallow striation without distinct levées tends to be produced. In some cases, the track of an indenting tool producing a striation reveals that the tool did not scratch continuously across a surface but rather moved in a percussive manner, producing a series of subparallel transverse percussion gouges (chatter marks). A final aspect of striation formation is that although the indenter must be sufficiently sharp and be able to hold a cutting edge for some distance, striation can only occur if the surface of the clast or bedrock can retain the scratch mark, thus soft materials and those easily weathered do not carry striations. Figure 2: Striations visible from left to right as deep grooves and multiple generations of striations at slightly oblique angles. Lineations from top to bottom are cracks and joints in the bedrock. ERSC/GEOG 2P05 3 Be certain to watch the introductory video Procedures 1. Plot striae from each site (data in the Excel file provided) on separate Rose diagrams. Those data are taken such that they capture the direction of ice flow, that is the trend from the ‘top’ of the striation to the ‘tail’. (15 marks) 2. Compare the general striation directions between the sites by visual inspection of the Rose Diagrams. (1 mark) 3. Statistically compare the striation sites with the null hypothesis: “that all three sites are sufficiently similar to be from the same ice movement”. You are going to want to watch the video/PowerPoint presentation for this. (6 marks) 4. Discuss the significance of your findings in a half to one-page commentary. (10 marks) 5. Compile all of this into one document, save it as a PDF, and upload it for grading. (required) PowerPoint Presentation Lab 5 – Striae and a Comparison of Striation Direction ERSC/GEOG 2P05 Mt Robson The Robson Glacier Athabasca Glacier – Part of the Columbia Icefield, Alberta. Cross-cutting relationships So how do striations form? Glacial Striations Depth, width and length of the striae depend on: Basal ice stress levels Ice velocity Meltwater presence Debris concentration (and clast lithology) Properties of the underlying lithology. (What would preserve a striation better, soft or hard rock?) Hudleston, 2015 Measuring Striations Check out the video on Sakai. Remember that striations are not the only indicators of flow direction. 1) Plot striae from each site on separate Rose diagrams. 2) Visually compare the general striation directions between the sites. 3) Statistically compare the striation sets using the null hypothesis “that all three sites are sufficiently similar to be from the same ice movement” 4) Discuss the significance of your findings in a half to one-page commentary Discuss how striations are formed (MUST BE PROPERLY CITED) Comment on how the visual comparisons of your rose diagrams are/are not supported by your statistical tests Discuss any relevant observations within the context of ice-flow history (i.e., sustained uni-directional flow & complete overprinting vs. cross-cutting relationships & potential multiple ice-flow events, etc.) Interpret direction(s) of palaeo-ice flow Mark Breakdown Plot striae from each site on separate rose diagrams. (/15) Visually compare the general striation directions between the sites (/1) Statistically compare ice flows (/6) Discussion (/10) /32 Due dates will be set by the course TA’s ANOVA T-tests are used for statistical comparison between two data sets, or between one set and a “true” value ANOVA is very much like a t-test among several (>2) data sets simultaneously but ANOVA utilizes the F-distribution instead of the t-distribution ANOVA and Hypothesis Testing H0: “that all three sites are sufficiently similar to be from the same ice movement” (μ1=μ2=μ3) H1:At least one of the sites exhibits striae trends which are significantly different from at least one other, such as to indicate ice movement during a separate episode. Conducting ANOVA in Excel Tools > Data Analysis: Single factor Two-Factor with Replication Two-Factor without Replication How many factors do we have? One factor = one independent variable Striation direction is our independent variable We have a SINGLE factor sampled across THREE sites ANOVA output EXAMPLE: Accepting or Rejecting the Null Hypothesis F > F critical Reject H0 P < 0.05 (chosen significance level) reject h0 sheet1 site 1 east sidesite 2 west sidesite 3 rock platform of quarry rdof quarry rdrood's bay 186243175 121256213 234191166 244321271 190358290 350189345 277277177 231224211 298272233 180301180 244223319 175324256 199278276 199297188 321271127 222255176 320309183 279233201 299215291 243301222 198198267 207194279 274233192 130267236 246212177 sheet2 sheet3 0.05="" (chosen="" significance="" level)="" reject="" h0="" sheet1="" site="" 1="" east="" side="" site="" 2="" west="" side="" site="" 3="" rock="" platform="" of="" quarry="" rd="" of="" quarry="" rd="" rood's="" bay="" 186="" 243="" 175="" 121="" 256="" 213="" 234="" 191="" 166="" 244="" 321="" 271="" 190="" 358="" 290="" 350="" 189="" 345="" 277="" 277="" 177="" 231="" 224="" 211="" 298="" 272="" 233="" 180="" 301="" 180="" 244="" 223="" 319="" 175="" 324="" 256="" 199="" 278="" 276="" 199="" 297="" 188="" 321="" 271="" 127="" 222="" 255="" 176="" 320="" 309="" 183="" 279="" 233="" 201="" 299="" 215="" 291="" 243="" 301="" 222="" 198="" 198="" 267="" 207="" 194="" 279="" 274="" 233="" 192="" 130="" 267="" 236="" 246="" 212="" 177="" sheet2="">