Teaching with sedimentation videos
Here's a ready-to-go handout with two videos, instructions, and a layout for student responses.
Geological Importance of the Sedimentation Process
Deposition of sedimentary grains is a process associated with weathering and transportation. On Earth, sedimentary particles are both carried by water and wind. Study of these processes enables scientists to better understand these systems and the sedimentary record in ancient rocks on Earth. Because similar sedimentary features have been recognized on Mars, our knowledge about earthly processes has been applied to understanding the modern and ancient geologic history of Mars.
Deposition of Sand from Wind
The deposition of sand by wind is a fascinating yet complex process. A multitude of individual grains interact with moving molecules of gas and with nearby sand particles, all the while under the influence of gravity and other dynamical forces. Yet out of all of this complexity arises fundamental form when the sand comes to rest on the ground. The remarkable consistency and stability of a simple sand dune has long drawn the attention of scientists who now apply our earthly knowledge of sand dunes to similar features on Mars.
Sand Angle of Repose on Dunes
The study of dune form and the classification of dune shape is a part of the study of the desert environment in an introductory earth science course. The "angle of repose" is the angle at which the downwind dune face lies when at rest with respect to the horizontal ground. Students typically study static illustrations of the angle of repose and learn its value (about 30 to 35 degrees).
Video of Formation of Sand Angle of Repose
Scott wanted more than just a nicely colored textbook illustration from which students would only learn a few facts, such as dune shape and the value of the angle of repose. So he assembled some low cost parts and experimented with his cellphone camera to record a close up view of falling sand as it forms a mound similar to that of a dune in the desert or on a coastal beach. (Scott also made a video about how he made recorded videos on his cellphone. Check out his project here.)
Extending Student Engagement with Video
Scott's purpose in creating these videos was to increase student engagement and extend student use of higher cognitive processes (Bloom's Taxonomy). So Scott created a "video tutorial" handout for students to fill in as they watched these videos, and afterwards, when they would discuss and address questions among themselves.
An "answer key" is not provided because different instructors may have different expectations of detail and expression for student responses.
Instructions to students include terms typically included in Bloom's Taxonomy so that students may be challenged to employ higher order thinking skills that span multiple cognitive levels.
Video Tutorial - Sand Angle of Repose
Student Handout - Sand Angle of Repose
Instructions to Student:
In this exercise, we will distinguish two terms (adapted from Merriam-Webster Online) to help guide our observation and response to the videos.
– something existing or occurring
– the explaining or expressing the meaning of something
Part I: You will see a laboratory experiment in which clean, dry sand (about 50 ml) is dropped onto a flat surface. Watch as the pile builds, make short notes in a bulleted list, and address the following instructions and questions.
- Notes to myself as the pile builds (e.g., interesting observations). Describe the shape of the pile as it builds.
- Sketch an outline of the pile at end of the first video. Add to your sketch lines that represent the angle from the horizontal of slope of a side of the pile.
- Estimate the value of the angle (in degrees from the horizontal surface) of the slope of a side of the pile after it is built _____________.
More Sand on the Pile
Predict what might happen when more sand is piled on top of the initial mound.
Part II: In the second video, a volume of sand equal to the first is added onto the top of the pile. Observe carefully the movement and flow of the sand as drops onto the pile. Write your responses to the following instructions and questions.
- One hypothesis - when 100% of the original sand volume is added to the first pile, the pile will then have twice the original amount of sand. Did the pile become twice as high? _________.
- Explain your answer to the question above with a sketch and description of relevant observation(s).
Part III: A portion of the video was run In slow motion so that you could better observe the flow of the falling sand grains and the build up of sand on the surface of the pile.
- Describe (bullet list) the motion of the sand added to the top of the pile during the slo-mo segment.
- Explain how this motion might keep the pile from growing as much in height as you might have expected.
Video Tutorial - Settling of Mud in Water
Here's a ready-to-go handout with a time-lapse video, instructions, and a layout for student responses.
Student Handout - Time Lapse of Mud Settling in Water
Instructions to Student:
In this exercise, we will distinguish two terms (from Merriam-Webster Online)
FACT – the quality of being actual; something that has actual existence or occurrence
INTERPRETATION – the explaining or expressing the meaning of something
Some backyard mud was mixed into a bottle of water, and poured into a glass cylinder. A photograph was taken every 8 seconds, over about 2.5 hours of time. The image sequence was then assembled into a movie file.
In Part I, watch the video, notice the elapsed times, and observe the cylinder for changes over time in the watery mixture. Make notes about facts as you watch the video to describe changes that you see. Then discuss with your peers interpretations of facts, and record your interpretations in Part II.