It’s an abnormally hot day in September and I’m standing in a cattail marsh in eastern Wisconsin, trying to change the way my students view the world. They’re all distracted—by the heat, homesickness, or the fact that they’ve lost a phone signal. The guys on the university hockey team are snickering about something. I’ve brought them here, in the first week of our introductory geology course, to investigate a mystery: Just in front of us, rising improbably from the flat expanse of the marsh, is a hill. About 50 feet high and twice as wide, it is made up of layers of loose sand and stones of many types. As we climb to the top, we can see that the hill snakes across the landscape like an upside-down river valley. My question for the students is: How did it form?
Geology has a PR problem; people associate it with musty museum collections and avaricious mining companies. As I hope my students will learn, though, looking at the planet through a geologic lens is something like strapping on an augmented-reality headset. It invites you, from your vantage point in the present, to summon up Earth’s deep past and far future—to see these parallel worlds with your own eyes, like digital overlays. Not far from the marsh, for instance, is a limestone quarry. The slabs of gray rock seem unchanging now, but your headset reveals that they were once a coral reef in an inland sea. Below the former reef is a layer of golden sandstone, whose perfectly round quartz grains, pounded smooth by the ancient surf, speak of a beach that existed long before life came ashore. There are AR tools for mapping and modeling, but so far none is as immersive as geologic insight.
From the crest of the serpentine hill, I coax the students into posing hypotheses about its origin. They try various overlays. Was there a river here once? That would account for the sinuous form but doesn’t explain why it’s a ridge, not a valley. OK, how about a glacial deposit? That explains the variety of stones, but a bulldozing ice mass doesn’t leave behind neat layers. The students are getting curious, drawn into the mystery, a little aggravated by it. Suddenly, someone has a crazy idea: Maybe this whole area used to be under ice, and maybe we’re standing in the dried-up bed of a river that flowed in a tunnel under the ice. The headsets are working now: We’re just 20 minutes from campus, but we’re half a mile under a Pleistocene glacier. The mood on the bus back to campus is buoyant. We’ve connected with something old, wild, and real.
Most humans are chronophobes. We worry about where the time has gone, whether we’re spending it wisely, how much of it we have left. Geology puts things in temporal perspective; it reminds us that, while the current version of the world is ephemeral, it’s also intimately connected to countless others, long past and still to come. If I’m successful, my students will finish the class seeing backstories everywhere in nature, their sense of place and time on this old Earth irrevocably altered.
Marcia Bjornerud, a professor of geology at Lawrence University. Her book Timefulness comes out this month.
This article appears in the September issue. Subscribe now.