I have attached all the documents needed for this lab.
1 ERSC / GEOG 2P05 Drumlins Drumlins are roughly ovoid-shaped hills of dominantly glacial debris that typically occur within groups or fields of several thousands. Drumlins exhibit very strong en-echelon long-axis preferred orientation paralleling the main direction of ice flow. The classical shaped drumlin usually has a steeper stoss end and a tapered lee-side, however variants on this shape are perhaps more common than the classical shape itself (Fig. 1) Drumlins may range in height from 5 to 200 m, in width from 10 to 100 m and in overall length from 100 m to several kilometres. Drumlins are such striking landforms that for many years little cognizance was taken of their internal composition. Drumlins are composed of a vast range of sediment types of varied provenance, containing an array of sediment structures and forms. The question of drumlin formation has attracted a vast array of research work (Menzies, 1984: Menzies and Rose, 1987, 1989) (Table 1). Figure 1. 2 Any explanation of drumlin formation needs to account for: (1) the varied location of drumlins and their close association in fields; (2) the diverse shape and morphology of drumlin form: (3) the enormous range in sediment type and structures within drumlins; (4) the existence of rock-cored and non-rock-cored drumlins, often in proximity to each other; (5) the presence of drumlins in bedform continua in some but not all cases; (6) the relationship of drumlins to subglacial glaciodynamics and hydraulics; (7) the chronology of drumlin formation whether drumlins form simultaneously as a single field or develop into a field by repeated ‘overprinting’ in a single glacial phase or repetition over several glacial phases; (8) stages of drumlin development whether formed en masse or by gradual accretion in a single continuous event or interrupted accretionary events; and finally, (9) a ‘trigger’ mechanism(s) needs to be found that is operative in certain specific conditions yet not under others. At present, three main groups of drumlin forming hypotheses can be identified: 1. Formation by moulding of previously deposited material within a subglacial environment in which a limited amount of subglacial meltwater activity occurs. Meltwater may influence moulding and deformational processes that are subsequently produced by acting either as a lubricating basal film at the upper ice-bed interface or as debris-held porewater thereby reducing 3 subglacial effective stresses. Debris is moulded by direct deformation of previously deposited sediment (both glacial and non-glacial) into drumlinoidal shapes by direct basal ice contact following some type of smearing-on or sculpting process(es). 2. Formation resulting from anisotropic differences in the subglacial debris (under dominant M- bed conditions) owing to: (a) dilatancy; (b) porewater dissipation; (c) localised freezing; (d) localised helicoidal basal ice flow-patterns; or (e) localised subglacial debris deformation. Within this specific group, meltwater activity is of limited impact, whereas porewater is considered critical in mobilising or immobilising local bed debris. The debris is not usually considered as being in a state of mobilised deformation except in case (e). It is suggested that changing stress field and/or stress/strain histories owing to transient basal glaciodynamics locally affecting subglacial debris rheology are the important parameters in determining whether drumlins begin to form or not. 3. Formation resulting from the influence of active basal meltwater carving cavities beneath an ice mass and later infilling with assorted but predominantly stratified sediment or by the subglacial meltwater erosion of already deposited sediment at the upper ice-bed interface. This hypothesis stems from the presence of stratified sediments in drumlins either in part, in leeside positions or through the entire drumlin, or the sculpting by fluvial processes of previously deposited sediment. This form of drumlin development, as with the hypothesis in (1), requires a two-stage process of initiation, beginning first with either a pre-formed cavity or pre-existing sediment at the upper ice-bed interface. The latter stage need not be linked directly to the former stage, therefore in some cases although conditions may be suitable for initiation for the first stage, the second stage may not continue towards the critical point (trigger) of drumlin development. In all of these hypotheses the conditions at the subglacial interface(s) are the key to subsequent drumlin formation and, in the long term, to drumlin ‘survival’. A complex relationship must exist between basal glaciodynamics, subglacial sediment rheology and hydraulics for any particular area of ice bed. Fluctuations in state or stress levels or meltwater production and pathways will affect all other parameters to some degree. Certain fluctuations may cross critical thresholds that cannot be reversed, while others may exhibit varying degrees of hysteresis. The likelihood or 4 otherwise of subglacial conditions occurring in any or all of the hypotheses remains a fundamental research problem. Reference Menzies, J. (ed.) 2002. Modern & Past Glacial Environments. Butterworth-Heinemann, Oxford, U.K. 543 p. Procedure 1. Select 15 drumlins on the section of the Livingstone Lake topographic map provided. Measure their maximum length, and width. Estimate their maximum height above the surrounding terrain. Measure their orientation to magnetic North. • A PDF and Jpeg are provided. You can print the map to work with manually or do your work using whatever digital tool you may have access to. Be sure to scale your measurements to meters based on the scale provided as accurately as you can reasonably do. • Please be careful if doing the work digitally to use the same zoom level for measurements and measuring your scale bar or your results will be meaningless. Contour intervals are 10 meters. • It is strongly suggested that you mark each dumlin (e.g., a, b, c) and record the measurements so you can easily remeasure if you’ve made an error. 5 2. Plot the length/width, width/height, length/height of each drumlin on 3 separate graphs. • Your plots should be prepared in Excel (or equivalent) and be in the form of scatter plots • For length/width plot make length the horizontal axis and width the vertical axis. • For length/height plot make length the horizontal axis and height the vertical axis. 3. Plot orientation of each drumlin on a Rose diagram. • Your Rose diagram should be clearly labelled and neat. Add, at each populated interval, the count of drumlins that are placed in that point. It is acceptable to make your Rose diagram digitally or by hand. If made by hand you will need to paste a clear picture of the Rose diagram in your report. 4. Discuss hypotheses of drumlin formation considering the plotted measurements. • Your discussion (excluding list of references) will not exceed 2 pages/800 words. • Cite sources, ideally in APA format. • Wikipedia is not a citeable source, do not cite Wikipedia, do not cite websites not affiliated with a research institution. As always Wikipedia may point in the right direction to sources. Valid sources are textbooks, academic journal articles, and government agency reports (which may cite other useable sources). 5. Compile your work into one document and save it as a PDF to upload to Sakai. This document will include: • Your measurements, and ideally a marked-up image of the map where you have made those measurements. • Two scatter plots as detailed above. • A Rose diagram of orientation • Your discussion on drumlin formation as it relates to your measurements. An example drumlin measurement: • In this instance on the map the drumlin was measured to be 23.5 mm ling and 7 mm wide at the zoom-level at which the map was measured. • At that zoom-level, the 1km (1000 m) bar on the scale measured 18 mm. • So if 18 mm = 1000 m, then our length of 23.5 mm = (23.5/18)x 1000 m = 1306 m • Our width of 7 mm = (7/18)x1000 m=389 m. • The orientation of this drumlin (always measured from north at 0°) is 060° NE. It is up to you to interpret the direction of ice flow from that orientation and the morphology! • Using the contour lines we can see the drumlin outlined from 490 m to 530 m. So, the height is estimated to be 40 m. The map contour intervals are 10 m as stated on the map section. Drumlins Drumlins Lab 2 ERSC/GEOG 2P05 What are Drumlins? 2 The Lab The Lab Collect and plot your data: Length/Width Width/Height Length/Height Measure orientation (Rose Diagram) Start by identifying your stoss end and lee slope The Lab Discuss possible hypotheses of drumlin formation in light of the plotted measurements. Direction of flow? Average height/width/length? Is there notable variation? Why or why not? Mark Breakdown Measure the morphologies for 15 drumlins . (/5) Scatter plot of length/width (/3) Scatter plot of length/height (/3) Scatter plot of height/width (/3) Rose diagram of drumlin orientation (/4) Discussion (/7) Discuss results Discuss drumlin formation Relate results to drumlin formation Cite sources /25 Due dates will be set by the course TA’s