In-Class Activity 2_Vast Deserts on Mars
Julia Kahmann-Robinson PhD and Marjorie Chan PhD, University of Utah Department of Geology & Geophysics
Expose students to the existence of the rather strange geomorphic features that are ventifacts. Students will be able to determine, or at least consider, that ventifacts exist on Mars.
Depending on your mode of delivery (in class versus perhaps a homework setting), load the Image File .ppt for the class and make sure you have an Internet connection to view the associated videos.
- Mojave Desert Ventifact Video: http://www.youtube.com/watch?v=OOqOm3KgGMw&feature=endscreen
- Mars ventifact images: http://www.psi.edu/pgwg/images/jul09image.html
Have students observe the large ventifact in Death Valley (see Image File, Photo by Marjorie Chan)
- What formation seems odd to the students? Have they seen anything like it? Why is there only 1? [there are very few this size in the Park actually and it is poorly understood why this is the case]
- Ask students to hypothesize how this might have formed. [Encourage students along a line of thought leading to eolian processes i.e. Death Valley receives little rain etc.]
Ask students to view the following video and answer the following questions. Start a discussion with your students. http://www.youtube.com/watch?v=OOqOm3KgGMw&feature=endscreen
- What do you look for in order to determine if a rock or feature is a ventifact? [ridges, facets]
- How can you discern which direction the wind was/is blowing? [the direction of the facets]
- What is the reddish-orange color due to? [Fe minerals in the rock oxidize when waters have remained under the rock for an extended period of time]
Definition: Ventifact- A rock that has been shaped or polished by the sandblasting effect of wind-blown sand
Here are what might be considered ventifacts on Mars: http://www.psi.edu/sites/default/files/imported/pgwg/images/VentFig4.jpg
- Bring up images on the screen (see Image File) or provide laminated copies upon which students can make annotations
- Ask students to label the wind direction on each: A thru G.
- Discuss with students the preservation potential of these eolian reworked deposits.
- Do students expect that they are easy to preserve? [In Death Valley they are not ubiquitous suggesting that preservation potential or formation is not common or easy.]
- Is the preservation potential higher on Mars or Earth in their opinion? [Mars likely has a higher preservation potential due to the lack of constant flowing surface waters.]
- Do any of the students doubt that the formation, in any of the images, is a ventifact, why or why not? Which images can they be sure of and why?
- Discuss student ideas and their understanding of ventifact formation and their indicators for wind current direction.