THINKING STRATEGIES FOR TEACHING ABOUT EVOLVING COMPLEX EARTH SYSTEMS

A central challenge to students’ understanding of the Earth is that the geo-/hydro-/atmo-/ biospheres exist only because they are far from equilibrium, and continuously exchange energy/materials through +/- feedbacks. Furthermore, the spheres evolve through 3 distinct mechanisms— elaboration, fractionation, self-organization—resulting in a complex co-evolution that increases the Earth’s diversity/complexity/interconnectedness through time. For example:

• The fractionating evolution of atmospheric gasses over geologic time has been largely mediated by but not limited to biological processes;

• Thousands of years elaborating evolution has little influence on fractionation, but at geological time scales the evolution of biological elaboration has changed the way that chemical fractionation occurs;

• The fractionating evolution of the atmosphere has at times changed opportunities for elaborating evolution and subsequently the long-term evolution of life on Earth.

In order to form a “theory of the Earth,” the Next Generation Science Standards (NGSS) provide performance expectations across grade bands that build an understanding of Earth systems through Grade 12. Still, teachers are challenged to effectively represent these complex Earth systems, typically because they have little opportunity to study them through teacher preparation or professional development. Understanding complex Earth systems requires skills a novice needs much time/effort to acquire. Although mathematical modeling is the scientists’ tool, the human mind is built to think in terms of narratives, or stories. If we do not first systematically develop the narrative, teachers’ (and their students’) ability to understand is limited.

We present a spatial/temporal narrative model of the evolutionary relationships among the spheres designed to introduce secondary Earth science and introductory college students to complex Earth systems. The narrative model is then translated into tools such as box models (stocks/flows, sources/sinks, reinforcing/balancing loops, etc.) during professional development and instruction to examine the specific interconnections and feedback mechanisms among the spheres that explain their co-evolution. These tools represent possible pathways towards meeting NGSS Earth systems outcomes.