Carving Mars: Rivers
In-Class Activity 1
Julia Kahmann-Robinson PhD, University of Utah Department of Geology & Geophysics
Observe the formation of fluvial channels, the effects associated with varying water velocity and changing base/level gradient, and the evidence for fluvial/alluvial environments on Mars.
- Acquire red/blue glasses to view HIRISE red-blue anaglyph images: http://www.rainbowsymphonystor e.com/maopandsproc.html
- Expose students to fluvial styles and fluvial processes (meandering vs. braided channels, base level fluctuation, changing stream gradient etc.) on Earth and how they are formed prior to conducting this In-Class Activity.
- Stream Table by Davidson Geology: meandering river- http://www.youtube.com/watch?v=YsQ7hW2fAEs&feature=related
- Eberswalde Delta-HIRISE: (context) http://hirise.lpl.arizona.edu/PSP_001534_1560 Image: http://hirise.lpl.arizona.edu/images/2007/details/cut/Eberswalde-delta-3x.jpg
- MOLA global map: http://www.google.com/mars/
- Meander Scar Image Source: ftp://eol.jsc.nasa.gov/EFS_highres_ISS022_ISS022-E-19513.JPG
- Water flows on Mars (choose the video under "Possible Water Flows on Mars"): http://mars.jpl.nasa.gov/mro/multimedia/videoarchive/
Show the following You Tube video of the Colorado River: http://www.youtube.com/user/oarsweb?v=QYoBC0qIn_8 After showing the short clip, ask the students the following questions, and show the video again so they can think about these different aspects of the river.
- Have students think about the following before showing the video:
- Where is the river fast? [Direct students to look to the middle or periphery of river.]
- Why did the large sandbar form (where the rafters camp)? [As the river cut, the slow section of the river deposited the sand bar.]
- Why do rapids form? [changes in river gradient, width of channel, drop in volume exposing more obstacles to flow]
- Why does the river form bends? [low gradient, slower stream velocity]
Have the students observe the Davidson Geology stream table experiment:
- Students should sketch and label the timestamp associated with the following fluvial events:
- Formation of a cut bank
- Formation of a point bar
- Stream avulsion
- Formation of multiple channels (at least more than 1)
- Cut bank
- Point bar
- Stream avulsion
- Multiple channels
- Cut bank
- Point bar
- Meandering vs. braided
Explore the HiRISE anaglyph image of the Eberswalde region of Mars:
Use red-blue glasses (blue filter over right eye) to view the following image: http://hirise.lpl.arizona.edu/images/2007/details/cut/Eberswalde-delta-3x.jpg
Ask the students the following questions:
- Are any of your stream table sketches similar to what you are observing on Mars? Which one, if any?
- Explain the circumstances in which this surface geomorphology on Mars might have formed.
Students can use Google Earth to show continental areas on Earth (e.g. look in high mountainous areas) where multi stacked channel style are prevalent. Do the same for braided vs. meandering styles. In doing so, discuss the following concepts:
- Channel gradient
- Sediment input
Make a Mars global map available for students to view digitally or hardcopy: http://www.google.com/mars/
- Consider the landscape of Mars. In what regions, could water have flowed as braided channels? Ask students to label a map or directly point out their response.
- Would meandering or braided fluvial styles be more common on Mars? How does this differ from Earth, or does it?
Have students use a Mars image or image they sketched from the stream table demonstration and ask:
- Where would it be safe to build a house?
- Where is deposition occurring? What about erosion?
- When students see the following scars:
- What does this tell you about the meanders?
- Can you students discern which meanders are older and which are younger?
- Did you observe similar geomorphology on Mars?