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Stealing data: Deriving bedform phase diagrams

Stealing data: Deriving bedform phase diagrams. Tom Hickson University of St. Thomas St. Paul, MN. Images of graphs from From Middleton & Southard have been removed from this presentation. Where they’re going. Interpreting cross stratification in a real section they’ve measured in the field

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Stealing data: Deriving bedform phase diagrams

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  1. Stealing data: Deriving bedform phase diagrams Tom Hickson University of St. Thomas St. Paul, MN Images of graphs from From Middleton & Southard have been removed from this presentation

  2. Where they’re going • Interpreting cross stratification in a real section they’ve measured in the field • Section contains low angle planar lamina, trough x-strat at many scales, and HCS

  3. Where they’re going…

  4. The goals • I didn’t want to just lecture on bedforms and bedform phase diagrams • I wanted students to derive them on their own and really explore them • To drive home the link between cross stratification and physical processes • To get them to make estimates of actual velocities and water depths from observations of x-strat

  5. Let’s work through what I do… … I sure hope that you have laptops…

  6. The process • Show them the progression from initiation of motion to antidunes (in a flume, using video, whatever) • Now, they must imagine doing many experiments, with different grain sizes, depths, and velocities • Give them the raw data and have them derive the results

  7. Show them the bedform progression • This part you’ll have to imagine • We go use a flume • Initiation of motion  Small ripples  Large Ripples/Dunes  Upper plane bed  Antidunes

  8. Videos from Paul Heller’s site can help

  9. Visualize doing this experiment many times • Different flow depths • Different flow velocities • Different grain sizes

  10. Give them the raw data and have them derive the results Now is where stealing data comes in… I ‘stole’ the data from original data plots in Middleton and Southard (1983)

  11. GETTING the raw data

  12. GETTING the raw data • DataThief III • Shareware • Java runtime so it works on just about every platform • http://www.datathief.org/

  13. An excellent jigsaw • Three Excel data files correspond to three grain size ranges • Each group of 3 students is responsible for one of them 0.1-0.14_mm_sand.xls 1.3-1.8_mm_sand.xls 0.5-0.64_mm_sand.xls

  14. In your groups: • First, understand what your data are… • Second, figure out a way to plot these data in Excel that will show the different bedform types in depth/velocity space • Make the plot (try it with linear and log-log axes) • Using Excel’s line-drawing capability, group the bedforms into logical ‘fields’ or ‘groups’

  15. Give them the raw data and derive the results Medium sand data file

  16. Depth/velocityphase diagrams From Middleton & Southard

  17. Re-arrange the groups • One representative from each grain size group • Derive the full three dimensional relationship for bedforms by answering this question: • How does grain size influence the bed state in unidirectional flows?

  18. What else do they learn? • A lot about Excel: sorting, plotting, grouping data in plots, how to you ‘help’, line drawing and labeling. • What makes a good graph? • How we use experiments to constrain our field observations • Can you think of others?

  19. Other classic data sets? • QFL diagrams of the Great Valley Sequence and unroofing of the Sierra Nevada

  20. LINKS • Data files at: http://serc.carleton.edu • Datathief Java Runtime app: http://www.datathief.org/ • Movies of different bedforms: http://faculty.gg.uwyo.edu/heller/sed_video_downloads.htm

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