Teaching about Systems

Most environmental issues involve near-surface earth systems that often exhibit complex characteristics and dynamics. The nature of near-surface earth systems often present major difficulties to students in their development of authentic, accurate conceptual models of earth systems and their ability to develop alternative solutions that address environmental problems involving these systems. Our research has explored the nature of student's conceptual models about complex earth systems, the nature of authentic inquiry and design involved in student's learning activities, and the impact of cognitive apprenticeship in improving student's reasoning about complex Earth systems. This work has led us to hypothesize that scaffolding students' ability to reason about complex earth systems requires a research-based framework to guide the choice of case studies that form the core of authentic instructional activities. This talk explores the nature of near-surface earth systems that exhibit complex behavior, the cognitive and epistemological issues that students may experience in reasoning about these systems, and the design of instructional activities that engage students in authentic scientific inquiry and engineering design. Finally, I will offer an initial framework that could be used to classify case studies and model systems so rational sequences of instructional activities can be designed.

Stable isotope geochemistry is a standard tool used to study a variety of complex Earth systems. Applications range from using the isotopic composition of shells of calcareous marine microfossils, or gases extracted from ice cores, as climate proxies, to tracing the source of carbon in the atmosphere, to determining the diet of modern and fossil hominids. Understanding the principle of isotopic fractionation is particularly critical to deciphering Earth's past climates as well as the complex processes that govern present day climate. To give introductory-level students a fundamental understanding of the principles of isotopic fractionation, we use large white beans and small black beans (or peanut and plain M&Ms™) to represent the heavier and lighter isotopes, respectively. Students model several "evaporation" and "precipitation" events by separating the "isotopes," culminating in the formation of an "ice-sheet." Students also use a spreadsheet to formulate equations that describe what is happening in the simulation, and create a simple spreadsheet model to calculate the isotopic ratios and δ18O values of the simulated oceans, clouds, precipitation and ice sheet that result as the activity evolves. After performing the visualization and modeling activities, students move on and use actual δ18O values and relative abundances of microfossils from deep sea sediments to determine relative sea surface temperatures and interpret the history of glacial and interglacial periods. Prior to performing the visualization activity, students struggled with understanding isotopic fractionation. After completion of the activity they are better able to understand and interpret isotopic data, and extend their understanding to other isotopic systems.