Analytical and Numerical Insight into Lava Flows and Cinder Cones on Earth, Mars and Venus
Eric B. Grosfils,
Pomona CollegeAuthor Profile
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This three part exercise introduces students to comparative planetary geology using volcanology as the subject and both analytical and (for visualization of cone-building processes) numerical methods. Material properties of the lava flows at Amboy Crater are derived from geometric characteristics, then quantitative methods are used to predict what the same eruption would produce on Mars (and the Moon).
This exercise is suitable for an Introductory Physical Geology course or an intermediate level Volcanology course.
Skills and concepts that students must have mastered
Students could perform the exercise using just the information provided, but the experience is far richer if they know a bit about lava flows and cinder cones before proceeding, e.g. the meaning of terms like "viscosity" and "density."
How the activity is situated in the course
Content/concepts goals for this activity
This exercise helps students understand how different environmental conditions (e.g., temperature, pressure, gravity, etc.) affect the morphological outcome of physical geological "experiments;" how composition, viscosity and eruption style can't be inferred from volcano geometry (contradicting their textbook's claim); helps students gain exposure to the application of analytical equations and numerical models to geological problems, and gain some understanding of the benefits and perils of these approaches; assists students in learning about yield strength.
Higher order thinking skills goals for this activity
This exercise provides an opportunity for qualitative critical thinking and hypothesis formulation by challenging students to consider and then test how geological processes operate; it promotes an enjoyable opportunity for quantitative problem solving and analysis of quantitative results; it promotes connections between field observations on Earth and geological observations from elsewhere in the solar system; and finally the exercise promotes student exploration of more complicated processes and interactions using available software.
Other skills goals for this activity
This activity also promotes verbal discussion and group analysis of quantitative results.
Description of the activity/assignment
Comparative planetary geology requires understanding how geological processes are affected by changes in physical environment-each planet and moon provides an opportunity to refine our understanding of how physical geological processes operate. Volcanism is a great example of a major geological process highly susceptible to such variations. Students performing this exercise will constrain how "Amboy Crater" would look if the same eruption happened on the Moon and Mars. Part 1 of the exercise asks small groups to assess either the yield strength of the Amboy flows or the time required for the flow to travel a given distance. After discussion of the results, Part 2 asks students to characterize the dimensions of the same flow, if emplaced on Mars or the Moon (changing only gravitational acceleration), and the time required for it to form; they are asked to predict the outcome in advance. Part 3 uses "Erupt" freeware by Ken Wohletz to explore how gravity changes will affect cinder cone geometry; the model is tested first to see if it correctly predicts an Amboy-like geometry, and afterwards students are asked to brainstorm what other factors should also be modified to improve the accuracy of the simulation, and how these changes would be expected to affect the geomorphological outcome. Finally, Part 4 asks students to use simple ballistic equations, implemented via an online Applet (Stromboli), to constrain the launch angle and starting velocity for the eruption that formed Amboy Crater (modifications are supposedly underway to permit this applet to run with different values of gravitational acceleration and air resistance).
Determining whether students have met the goals
Do student calculations yield the correct answers (instructors, feel free to contact me for the key)? When they are asked to predict resulting geometries in advance and explain why the geometry of the lava flow or "cinder cone" on Mars would be different, can they do so? In Parts 2 and 3, do students identify complicating factors and reason through their effects in a plausible way?More information about assessment tools and techniques.
Teaching materials and tips
- Activity Description/Assignment (Acrobat (PDF) 153kB Apr10 06)
Listed within the assignment.