Since its the week before the GSA meeting in Denver, I was simply going to skip talking about the field trip I took yesterday with the intro lab. However, Anne raised the bar by posting a stratigraphic column today of southern Minnesota and two of the units in the local area are now staring me in the face.
Background: the introductory students here are divided into three labs (72 students total, so 24 per lab). For the first portion of the semester, they do the typical “here’s a mineral, now go and ID a tray of minerals; here’s a rock, now go and ID a tray of rocks” that most beginning geology classes cover. Once we finish with that segment of lab, we move onto a fairly creative project that involves two lab days driving around the greater St. Peter / Kasota region looking at the sediment & rocks to determine the geological history of the area. (Disclaimer: I just inherited the lab and get to wonder at its beauty, but don’t have any claim on the format or what we visit.) Because this is intro, the material is simplified a bit, but the local geology isn’t very complicated to start with. There are two rock units the students have to identify (the Cambrian Jordan Sandstone and the Ordovician Oneota Dolomite) and two types of Quaternary sediment (glacial till and alluvial deposits). The students visit all of the units several times at various outcrops around the area, draw contacts on their topographic sheets of the St. Peter quadrangle, and construct an east-west cross-section for the area.
Reality: yesterday was the first day of the field trip. Julie and I drove around a few weeks ago, so that I could visit all ten of the stops (we do 4 on the first day and the remaining 6 on the second day). When we previewed the trip, the river was still fairly high, but at least all of the roads were open. Julie gave me a good run-down of what is usually discussed at each stop & about how much time to spend on any given rock in order to return within our 2-hour window. Yesterday the river was lower, which made examining the alluvium deposits much easier. However, it was very, very windy, raining / snowing, and fairly darn cold. I had warned the students about the weather, so they were dressed appropriately (yay!), but it was still a fairly miserable day to be standing out on the side of the road. (Its also why I don’t have pictures…) But there were a few golden moments, when I saw lightbulbs actually go off:
- one student linked the glacial flooding we saw up on the voluntary field trip to Interstate State Park (which I still haven’t posted pictures from…) to the bedrock terrace found within the dolomite unit
- another student remembered the depositional environment of carbonates / well-sorted sandstones (what the Jordan sandstone is)
- several students quickly knew what deposited till
- I got a few quick teases as a road grader drove by about how it was demonstrating what I was discussing (which was how glaciers move sediment)
- they managed to ID dolomite, quartz sandstone, granite, and gneiss in the outcrop (the latter are present as erratics)
- a quick grasp of why the Kasota prairie was never farmed (lots of outcrops of the dolomite–which never would have stopped a New England farmer–that made the Quaternary deposits more appealing for farmers)
The students didn’t complain about the weather. They enjoyed going out and doing something “different” — a reinforcement of the idea that field trips are the way to go.