Thermal Exhumation Model
University of Illinois, Department of Geology
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Build a one-dimensional thermal model in STELLA of rock uplift. Determine how the speed of uplift affects the geotherm and why uplift rates determined from heat flow are often too high. The model demonstrates the Laplacian method of following materials in a model that significantly reduces the complications in creating the model.
Capstone course in modeling the earth and systems modeling. Generally juniors, seniors and beginning grad students in geology, geography, atmospheric science and earth science.
Skills and concepts that students must have mastered
Students should have familiarity with STELLA or other systems modeling programs (e.g. Vensim,...).Several preliminary weeks of simple models should enable them to construct models. Good analytic skills in general are helpful.
How the activity is situated in the course
This is one of a semesters worth of weekly modeling projects. It occurs about half way through the semester after some weeks of tutorials and simple models.
Content/concepts goals for this activity
The assignment is to model the heat flow into and out of a parcel of rock that is being exhumed (for example in mountain building). Using a Laplacian viewpoint, the exhumation can be modeled with one stock, two flows and two feedbacks. The goals are to understand how viewing a model a different way can simplify, how feedbacks work, and how boundary conditions complicate the model.
Higher order thinking skills goals for this activity
the project requires the ability to translate a three part partial differential equation, that of heat flow with conduction, radiation and advection into a simple one-dimensional model. It is a complex series of decisions on what parts to leave out, what time scale to use and what boundary conditions to use.
Other skills goals for this activity
Students also generally work in pairs on the models and report on the results, interpreting graphs and tables that the model generates. They must also come up with 2 analogous models that could be used in another context.
Description of the activity/assignment
One of the means investigators use to determine uplift rates in mountain building areas is the heat flow measurements. Heat flow is determined by the geotherm in the area which is often assumed to be linear, another way of describing that is conductive. Of course because the mountains are actively uplifting, then the heat flow has an advective component that must be taken into account that causes the geotherm to be non-linear (banana shaped). Students construct a simple one stock model that calculates the conductive heat flow out of an uplifting parcel of rock and graph the temperature vs. depth for vairous uplift rates and parcel sizes.
Determining whether students have met the goals
Students turn in a model with captioned report, answering questions on the results of the model they constructed. They must understand whether the model worked as they expected, what were the problems involved and why boundary values were an issue.
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