BUILDING A GEOLOGIC HISTORY FROM AN ARCHEAN TO PLEISTOCENE COLLAGE: LEARNING ABOUT GEOLOGIC PROCESSES THROUGH LOCAL GEOLOGY IN THE MINNEAPOLIS-ST. PAUL, MN, REGION

An intensive, field-based, 2-week course for local high school and middle school teachers was developed for the TIMES Project (Teaching Inquiry-based Minnesota Earth Science) by consolidating and adapting a variety of field trip-based components from University-level courses. The aim was to provide the teachers with an understanding of earth processes in the context of local Twin Cities (Minneapolis-St. Paul, Minnesota) geology. Our additional aim was to model inquiry-based approaches and constructivist learning through field-based observations and interpretations.

The exposed bedrock in the Twin Cities is an essentially flat-lying Paleozoic sedimentary sequence, which directly overlies basement rocks of the 1.1 b.y. Midcontinent Rift. Paleoproterozoic and Mesoproterozoic igneous and metamorphic rocks are exposed northwest of the Twin Cities in the St. Cloud region. Bedrock units are overlain by glacial and glacio-fluvial sediments ranging from 0 to 1000m in thickness.

In this course the teachers were introduced to ‘isolated’ components of the stratigraphic sequence, and through answers to their own questions, or the questions we ask of them, they learn to use principles of correlation and relative age to develop a rudimentary geologic history. Local geologists with expertise in a variety of geologic subdisciplines lead the investigation each day by posing a series of questions that will lead the teachers to recognize the geologic relations between the ‘isolated’ components. Rock units not present in the metro area are investigated through use of an urban walking tour of facing stone; we also use walls composed of till-derived boulders to investigate the variety of Archean and Proterozoic terranes of northern Minnesota.

Investigation of the bedrock geology is complemented by studies of surficial processes, such as stream gauging and calculation of waterfall retreat rates based on field observations in bedrock, till, and outwash units. A trip to the St. Anthony Falls Research Lab introduces the teachers to the role of modeling in surficial processes and basin analysis.