Please read first- the information given is a lot and tideous. the actual writing part isn't as bad.
The lab this week is in three parts. In the first part, you will study rivers using Google Earth. In the second part, you will use a few household materials to build a stream table model, to make observations about water flow firsthand. Before beginning this lab, take a few minutes to review the list of materials required to complete Part 2, on page 5. Also please note, that the stream table setup includes an overnight step. Contact your instructor if you have any questions.
Your final product for this lab, the third part, will be a lab report. It is not necessary to submit this worksheet. Your report should cover all of the questions you have answered here (in paragraph essay form, not question and answer format), as well as your stream table observations (including drawings and photographs). It should discuss how these two tools – Google Earth and a stream table – can be used to study different aspects of rivers.
Part 1: Observing Rivers in Google Earth
This lab assumes a working knowledge of Google Earth, which you should have gained by completing the first week's lab on plate tectonics. It also assumes that Google Earth Pro has already been installed on your computer (see Module One lab for instructions on how to do that.)
For each location you will be directed to in this lab, you have two choices. The first is to use the Google Earth search feature, following the instructions in this lab. The "workaround", if you have difficulty finding a particular location, is to use the Placemarks – Earth Rivers KMZ file, which can be downloaded from here: https://serc.carleton.edu/NAGTWorkshops/earlycareer2010/activities/45769.html (Links to an external site.). Upon downloading, the file should open automatically in Google Earth Pro.
Please note that the instructor is aware that there is an answer key file available from the same online location as the KMZ file. You are welcome to use it to check your answers here if you wish. However, your final lab paper should reflect original writing and analysis – not merely a repetition of the very brief answer key responses.
Let's get started! Open your Google Earth Pro – either directly from your computer, or by downloading and opening the Placemarks KMZ file.
- Locate Oxbow Bend (part of the Snake River in Grand Teton National Park, Wyoming). Observe the feature in Google Earth:
- What type of river is this, meandering or braided, and how can you tell?
- Discuss briefly the processes of erosion and deposition that are occurring in this area and why they are happening. What is the likely eventual fate of Oxbow Bend?
- Is there any evidence of this particular process operating in the past along this portion of the Snake River? If so, describe the evidence. If not, describe the evidence you would have expected to see but did not?
- Open the Oxbow Bend panorama (either in Google Earth or via the webpage https://www.thewave.info/GrandTeton/Oxbow%20Bend/index.html (Links to an external site.)). You can zoom in and out of the pan as needed. (Click 'Exit Photo' to return to the regular Google Earth view).
- Consider the processes of erosion and deposition you observed in Question 1: what evidence of these processes can you find in the panorama?
- Describe the Snake River plain as seen in the pan: the river plain extends from the foreground out to the base of the Tetons in the distance.
- Examine the river plain to determine if any river terraces are present. Describe the terraces you observe (size, how they likely formed), or suggest an explanation for why there are no terraces present.
- Locate Horseshoe Bend (near Page, AZ), which is part of the Colorado River east of the Grand Canyon. (Panorama a https://www.360cities.net/image/horseshoe1 (Links to an external site.)).
- First, explore this part of the Colorado River in Google Earth and describe the type of river present. How is this river similar or different to the portion of the Snake River you observed in Questions 1 and 2?
- Second, examine the location of Horseshoe Bend. What type of feature is this? How is it similar to and different from Oxbow Bend?
- Examine the panorama. Describe the Colorado River as observed in the pan: in addition, describe any terraces you observe (size, how they likely formed), or suggest an explanation for why there are no terraces present. What does this suggest about the geologic history of this part of Arizona compared to the portion of Wyoming observed earlier?
- Locate the drainage using the placemark "Drainage (CA)" or by searching for the latitude/ longitude 35° 8' 9.74"N, 119° 40' 29.25"W.
- What type of drainage pattern does this stream exhibit? How is this different from the Snake and Colorado Rivers?
- Suggest a reason for the drainage pattern observed here (zoom out and consider your location, especially the long linear valley associated with the stream).
- Find the location where the Volga River enters the Caspian Sea.
- What type of structure is this and how does it form?
Part 2: Observing Rivers Using a Stream Table
In this part of the lab, you will contrast a stream table and use it to experiment with river flow. We will follow the scientific method to explore how river channel morphology (shape) changes when a variable, like gradient (slope of the stream) and discharge (amount of water flowing in it), is altered.
To get started, and to get a sense of what you will be doing, check out a virtual stream video at the following location: Stream Table Timelapse (Links to an external site.).
- What landform develops over time where the river meets the water? (Hint: compare with what you saw where the Volga River enters the Caspian Sea in the Google Earth activity.)
Now let's set up a real stream table! Note: the set-up includes an overnight step.
Materials needed (where several choices are offered, best option is in bold)
- A rectangular tray or pan (paint roller pan, baking pan, or cookie sheet with sides)
- Play sand (not construction sand) or corn meal (plain – not self-rising)
- A single-use cup (Paper or Styrofoam)
- A paper clip or push pin to make a hole in the cup
- A pitcher of water
- Books or other objects of different thicknesses (to tilt stream table)
- Add sand or corn meal to about 2/3 of length of tray. Sand or corn meal should fill most of the height of the tray.
- Gently sprinkle water from the pitcher onto the clay or corn meal; allow it to soak in. Continue until the sand or corn meal is saturated.
- Leave your stream table to sit overnight.
- Set up your stream table with one or more books under one end, to provide slope for your stream.
- Using the pin or an unbent paper clip, make a hole in the side of the single-use cup, near the base. Make it big enough so that water can flow out of the cup at a fairly rapid rate. Have the pitcher of water available so you can refill your cup as needed.
Choose Your Variable:
For this experiment, you can choose either gradient (slope) or discharge (stream flow rate).
Make a Hypothesis:
Go back to your observations from the virtual stream table on page 5. Come up with a hypothesis (educated guess) as to what you think will happen with your stream channel when you alter your chosen variable. How might the stream morphology change?
- Record your hypothesis here.
Run the Experiment
Run your experiment. If you are altering gradient, run the experiment twice with two different levels of tilt to your stream table – I recommend making your second stream twice as steep as your first one. If you are altering flow rate, after the first experiment, make the hole in your cup noticeably larger (aim for doubled flow). To run your experiment, hold your empty paper cup about an inch above the filled end of your stream table, roughly centered between the two sides, with the hole facing "downstream". Fill the cup and let the water flow out of it and onto the sand or corn meal. Keep filling the cup and letting the water flow until your pitcher is empty. Record your results with a digital photograph; I recommend a sketch, too (which can also be photographed). You should include these visuals in your final report. Where did erosion occur? Where do you see deposition taking place?
Drain as much of the water as possible out of your stream table and smooth over the sand or corn meal. Change your variable (steeper slope or higher flow rate, but not both). Run your experiment a second time and record results again.
Accept or Reject Your Hypothesis
Accept your hypothesis if what happened matched what you thought would happen. Reject your hypothesis if it didn't.
- Accept or reject your hypothesis here. Why do you suppose you got the results that you did?
Part 3: The Report
Write up your lab in a well-crafted report. The report should cover all the questions from Part 1 and your experiment in Part 2. Also include a discussion of how these two tools for studying rivers, Google Earth and a stream table, reveal different aspects of stream morphology. What connections can you make between what you saw using your stream table and what you discovered on Google Earth? What have you learned about river processes and landforms from this lab? Include a title page, your digital photos from the stream table activity, and a list of any references you cited in your text.