Feedbacks are a critical part of many systems. In this unit, students use a systems model to explore the effect of positive (reinforcing) and negative (balancing) feedbacks on system behavior. Model results are then used as a basis for interpreting Arctic sea ice data. To complete the unit, students will ideally have access to free systems modeling software.

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This exercise is part of a sequence of exercises to help students understand single and multiple aquifer tests. In class, students will receive data from pumping tests at University of Minnesota's hydrogeology field site. Instead of using commercial software, students will create interactive modeling tools to facilitate curve matching and to collaborate on understanding aquifer tests at different scales using different methods. The approaches used in this exercise can be extended to develop models to compare single and multiple aquifer tests using different approaches.

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This computer-based assignment forces students to compare and contrast integral and differential forms of the conservation of mass equation, as well as analytical and numerical approaches to solution. Students are given a text description of a simple environmental problem (a conservative tracer diffusing in a one-dimensional system with no-flux boundaries) and are then required to first write equations that describe the system and then implement these equations in an Excel spreadsheet or Matlab m-file. Students then use their spreadsheets/m-files to compare different solution methods and must communicate these results in short text answers.

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Students are trained to use the Visual MODFLOW computer program (Waterloo Hydrogeologic, Inc.) and they learn first-hand how to apply the Dupuit Approximation to groundwater flow and transport problems in unconfined aquifers. The students apply the Dupuit Approximation (Fetter, 2001) to a case study developed from Anderson and Woessner (1992) in which they are given system dimensions, aquifer properties, and well water levels. Learning objectives include (1) prediction of groundwater flow and transport and (2) model calibration (e.g., getting the model output to match well water level data). Students also learn how to solve the equations using a computer spreadsheet program, further expanding their ability to understand and work with the equations.

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Students will fill in a blank periodic table for elements 1-20 using electron-dot models. As a visual tool students should see several periodic trends.

The activity walks the students through the processes of Photosynthesis and Cellular Respiration.

Students build a model of a watershed, apply water to the model, and explore what happens when elements of the watershed are changed.

Students vary the seismic P and S wave velocity through each of four concentric regions of Earth and match "data" for travel times vs. angular distance around Earth's surface from the source to detector.

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This is an activity to help students understand the abstract concept about how planets move around the sun and their relative size compared with other planets in the solar system.

Wind surge is a JAVA based applet for exploring how water level on the windward and leeward side of a basin depends on wind speed, basin length, water depth, and boundary type.

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