Imagine you’re nineteen years old again. It’s a crisp fall afternoon, and you’re looking out the window of a cramped college fleet van. You’re watching the mini malls of Wisconsin’s Fox Valley evaporate into farm fields. It’s the first field trip of the year in your new introductory geology class—the ambitiously named History of Earth and Life—at Lawrence University in Appleton.
You’re jostled awake from an unintentional doze as the van stops in some sort of marshland. Ahead, something strange: Out of the marsh rises a steep fifty-foot-high hill, scarred by an old gravel quarry dug into the slope.
The only instruction you’re given is to head to the hill, observe it, feel it, and figure out how the heck the landform got there. Your professor will answer questions but none that will give away the answers you seek. You and your classmates are told to work together; until you’ve figured it out, no one is leaving the marsh.
The architect of this devious pedagogical strategy is Marcia Bjornerud, a geologist and the Walter Schober Professor of Environmental Studies at Lawrence University and a Wisconsin Academy Fellow. Marcia is a nearly lifelong Wisconsinite, excepting some brief stints near and far afield in dogged pursuit of her beloved rocks. She lived her early years surrounded by the farmlands outside of Eau Claire, spending unrestricted days exploring the outdoors and practicing an early version of what she would eventually ask of her students in the marsh: observing and coming into relationship with the landscape around her.
As a child, Marcia never intended to become a scientist, much less a geologist. In school, science was not presented as a feasible path, and the way it was taught didn’t interest her—despite her reflection now that, even in her youth, she was already “a natural scientist of [her] own kind, observing phenology out in the woods” near her home.
But as a student in an introductory geology class at Carleton College in Northfield, Minnesota, something struck a chord. Geology, one of the more recently developed natural sciences, gave Marcia a language to describe the Earth she’d gotten to know intimately as a child. Etymology is the study of the origins of words; for Marcia, geology provided “an etymology of the world.” With this new language, she was entranced.
After a year in Northfield, Marcia transferred a short drive up Interstate 35 to the University of Minnesota–Twin Cities where she finished her BS, specializing in geophysics. Then she returned to Wisconsin to attend the University of Wisconsin–Madison for an MS and PhD in structural geology, a subdiscipline focused on “the architecture of the Earth’s crust” and the way the movement of tectonic plates deforms rocks in mountain belts.
In 1987, degree fresh in hand, Marcia completed a postdoctoral fellowship at the Ohio State University and then began a professorship at Miami University of Ohio. During the summers, she explored the high Arctic, researching ancient mountain ranges on Ellesmere Island in Canada and on the Svalbard archipelago in Norway. From her travel and research, she produced peer-reviewed papers that appeared in such publications as the Journal of Structural Geology and Tectonics. Then, in 1995, following a desire to delve more into teaching, Marcia took a job as a professor in the geology department at Lawrence University, where she still teaches and produces research.
However, if you were Marcia’s student, looking up from the base of that mysterious hill in a marsh, you wouldn’t be learning her biographical details. Instead, she’d want you to be learning the etymology of the Earth. She’d want you to be learning a native language you might not realize you already know how to speak: the language of an Earthling. In doing so, she’d hope that you would begin to glimpse yourself as part of the subtle and magnificent systems which that language reveals.
You and your classmates approach the hill. A few energetic students scramble up the loose gravel sides of the old quarry to get to the top as quickly as possible. You and your more careful peers instead pause to look closely at the loose sediment at the base. The shovels of bygone quarriers have offered you a window into the interior structure of the hill. Looking closely, you notice patterns emerging from the jumble of sand and gravel. Instead of being arranged randomly, the larger rocks seem concentrated in horizontal lines, with beds of sand in between. It occurs to you that somehow, some force has sorted this sediment into discrete layers based on the size of the grains. The person beside you murmurs that something about the rocks is strange—they don’t look at all like the limestone that is so common nearby. Suddenly, a shout rings out from the climbers above: “Everyone come up here! This isn’t just a regular hill, it’s long and wriggly, like a snake!”
You might be wondering, rightfully so, why we’re talking about words, language, and etymology in this profile of Marcia’s career in science. Marcia herself acknowledged the apparent disparity of linguistics and geology in a 1995 journal article, “Geolinguistics: Tracing the origins of geologic terms.” “One is about the supple, evolving brain, the other about hard, unchanging rock,” she says. But, for her, rocks and language have always been deeply intertwined.
Both words and rocks record the past. Words are records of human history and changing thought; rocks are an archive of our planetary saga. Understanding both holds the power to change how we see the world around us. In “Geolinguistics,” Marcia tells us that, “just as most people see rocks every day without giving thought to their origins, most people use words every day without recognizing their deep roots. One’s experience of a landscape is enriched, however, by an understanding of the geologic processes that have shaped it. Similarly, one’s sense of humanity is enhanced by knowledge of the origins of the words bequeathed to us by ancient peoples.”
The connections between rocks and words go deeper, though, than simply a similarity between the philosophies of geology and linguistics. Deeper, too, than the rich cultural history of the words we use to describe geologic phenomena (though there is plenty of that—for some examples, see Marcia’s most recent book Geopedia: A Brief Compendium of Geologic Curiosities). Marcia asks us to bring these philosophies into relationship with one another; when we do so, we begin to sense the many subtle yet profound ways that Earth speaks to us.
To appreciate what Marcia means by this, it is helpful to understand one of her fundamental precepts—that rocks and the Earth are, in fact, animate, active, and evolving. As she often says, “Rocks are not nouns, but verbs.” It can be tempting to think of rocks as eternal or timeless. After all, we deem permanent things as “set in stone.” But as Marcia explains, rocks “aren’t just there—they become. Each rock embodies an event, and in some cases, multiple events.”
Marcia becomes electric while teaching about this concept on field trips to Baraboo, Wisconsin, a place she knows intimately. There, a distinctive, somewhat glassy purple rock stands out spectacularly against the green trees and blue lake at Tewakącąk (known on settler maps as Devil’s Lake State Park). This rock is quartzite—a metamorphic rock consisting almost entirely of quartz, once buried deep beneath the surface. But this rock’s texture and markings reveal that this was once sandstone, whose origins were a tropical white-sand beach along an inland sea.
The Tewakącąk quartzite exemplifies Earth’s unique planetary mechanism for preserving and delivering its layered memories to the surface. It’s easy to imagine a planet where sediment piles up and volcanoes erupt, burying old rocks deeper and deeper, so that the only strata accessible are the most recent. On some planets, this is how sediments remain forever—the oldest rocks’ secrets are buried deep beneath the surface, never to be exhumed.
But here on Earth, plate tectonics disrupt this inexorable cycle. When plates of the Earth’s crust move and collide, some rocks involved are pulled deep into the Earth to melt and, eventually, form new igneous rocks. But others, like the Baraboo sandstone, are chaotically crumpled, folded, and wrinkled up into mountain ranges, where they very slowly erode to leave fresh windows into the past. The purple quartzite at Tewakącąk is one of these windows, the exposed core of an ancient mountain belt, where the intense heat and pressure at the heart of those now eroded mountains transformed the Baraboo sandstone to purple quartzite. Improbably, 1.6 billion years after the Baraboo beach was buried, lithified to stone, then violently crumpled into the heart of a mountain belt and metamorphosed, you can still touch its original ripple marks and be transported to an ancient shore, feeling the wind and waves that tossed the grains now part of this iconic purple stone.
In this way, Marcia tells us, rocks become storytellers. The quartzite at Baraboo tells a story of past environmental change. By tracking the shape of ripple marks in different layers, or strata, preserved from its sedimentary past, geologists can discern how the flow of water changed over a billion years ago. They can also see changes in the strata that show how sea level rose, as the lowest layers appear to be remnants of a calm-watered estuary or fossilized soil, while the top layers reveal the gradual inundation of those sandy beaches. These are tales the rock tells of past environmental change. By learning these stories at places like Baraboo, or from sediments on the ocean floor or ice cores taken from the poles, we come to better understand the limits and reactivity of Earth systems. Stories are the way humans pass down intergenerational memories and lessons. As Marcia imparts in Baraboo, the Earth also uses stories to pass down knowledge, if we learn how to listen.
Imagine you and all your classmates have now made it to the top of the sinuous hill. From this vantage, you can see that the sides are steep like a knife’s edge, and it does indeed wind across the marsh’s otherwise flat profile. As you catch your breath from the climb, Marcia begins to ask some questions to get the creative problem-solving started: “Now, how do you think this snake-shaped hill got here? Pose some hypotheses—it’s okay if you’re wrong.” There’s some silence. You have half an idea but don’t want to be the first person to say something wrong. The quiet becomes strained, everyone hoping somebody else will guess first. Finally, a voice behind you, tentative and questioning: “Maybe it was a river?” Ah, now the collaborative thinking has begun, but no, it can’t be a river. The shape is right, the curvature and the type of sediment are right … but rivers cut into the landscape and leave a valley, they don’t create a hill. Even though it was wrong, this answer breaks the silence, and now students are genuinely curious and eager to tackle this mystery.
Learning to listen to the Earth and its stories is difficult. Earth is a messy place, and its stories are complicated, intertwining, and cyclical. And, as Marcia tells us, a geologist or student of Earth systems has “to be open to the possibility that you’re going to see rocks of any habitat, anywhere. … You have to be familiar with all of these species of rocks and then be able to conjure up in your imagination what habitats those rocks represent.” As an Earth scientist, you must have the skills to interrogate and discern the vast library of rocks and minerals you might find at the Earth’s surface. You also need the imagination to take these identifications and weave them together into a coherent plot that tells a story of the environmental situations that could create such rocks and landforms. By applying these skills, you can begin to hear the Earth speaking to you.
Marcia has spent her career seeking ways to help her students learn these skills. It’s not an easy task. Some students, like Marcia herself, come to geology without thinking of themselves as scientists. In fact, sometimes it is exactly this feeling that guides them to geology in the first place: Biology, chemistry, and physics, with their test tubes and theoretical equations, seem too intimidating, but geology seems more tangible and hands-on. Students learn, eventually, that geology integrates all these fields, as it takes physical, chemical, and biological processes to make rocks, but the approachability of geology brings students in the door. Once they’re inside her classroom (or outside on her field trips), Marcia’s work begins.
Marcia’s educational philosophy is inspired by her own experience as a young geologist. She wants “everybody to feel welcome, and to know that they bring all the skills they need to do this particular science.” Her goal is to “try to coax out of people the latent scientist … in everybody.”
The detective work required on their first field trip each fall builds self-confidence in her students, who arrive in the marsh with no formal training in geology but, by the end of the day, have succeeded in reading the story of a landscape. Interspersed with this heuristic approach, Marcia delivers knowledge directly to the students. But by enabling moments of self-derived epiphany, she hopes her students “develop the habits of mind, confidence, and the instinct of how to go about thinking about the Earth.”
This is not to say Marcia thinks everyone should become a professional geologist. She believes that “the habits of geologic thinking are important for anybody,” ranging from the practical—“understanding where your drinking water comes from, or what climate change is going to mean for your particular community”—to the intangible—“that there is spiritual or some kind of existential comfort in understanding where you are in a local and more global sense.” For Marcia, geology offers a way to satisfy a “hunger to reconnect with place, this intrinsic, if unmet, need to feel connection.”
Marcia’s work to facilitate this sense of connection doesn’t end at the border of Lawrence’s campus. Her first book, Reading the Rocks: The Autobiography of Earth, published for a general audience in 2005, reveals the planetary history that Earth tells, and how we can read this history. In 2018, she published Timefulness: How Thinking Like a Geologist Can Help Save the World. This book explores the idea that pervasive chronophobia, or being “unwilling to think honestly about the power of time to change us and the world,” is the source of many environmental problems. She proposes the antidote of “timefulness,” the understanding that “everything is made by time and will continue to be altered in time … learning to live with that rather than somehow battling it or thinking we can do an end run around it or just ignore it.”
In 2022, she published the aforementioned Geopedia, and she is currently working on her fourth book, Turning to Stone: Discovering the Subtle Wisdom of Rocks. Marcia has also contributed to the New Yorker and written for the New York Times, Wall Street Journal, and Los Angeles Times, among many other publications. She’s appeared on numerous podcasts and radio programs. Through her writing, Marcia hopes to help her students and fellow Earthlings see their world in a new, richer, and more wonderous way.
The excitement builds as you and your classmates zero in on an answer. “Could it be a beach, like this was the shoreline and the waves pushed up all this debris?” A good thought, but beaches aren’t generally so curvy. Then you remember all those strange, foreign rocks your classmate noticed earlier at the base of the hill. Beaches don’t usually have rocks from lots of different places far away, you posit. A peer excitedly offers an idea: “Don’t glaciers bring rocks from far away? And wasn’t Wisconsin covered by glaciers in the Ice Age? Maybe this all got dumped here by the flowing ice and the glacier bulldozed it into a hill?” Not a bad guess. But wouldn’t that process jumble up all the different grain sizes? Why did you see layers? Even so, something about the glacier idea makes sense. You’ve seen photos of rivers on top of the ice in Greenland. “What if these rocks were moved here by a river on the surface of the glacier? Then when it all melted, this was left behind?” Just as your thought was sparked by your peer’s idea, the student next to you seems inspired by your proposal. “That seems close, but I don’t think the nice layers could have survived all the melting. Could there have been a river under the glacier? Since water always takes the path of least resistance, maybe it was easier for the river to erode up into the ice than to cut down into the land below?” You notice Marcia smile. The class has done it! Marcia confirms that you’re standing on top of what geologists call an esker, the deposit of a subglacial drainage channel. Of your epiphany, she’ll later write, “They can now hear the roar of turbulent water in the ice tunnel, flowing fast enough to move boulders. The esker is speaking to them, sharing its memories.”
While eskers are a common landform in formerly glaciated landscapes such as those in southern Wisconsin, if you live in this area, you might never have seen one—but that’s not because they were never there. The esker Marcia takes her students to tells us why they’ve vanished. The quarry in the side of the esker’s hill takes advantage of the subglacial river’s work to sort the sediment into deposits of sand and gravel that are valuable for construction. These have been so heavily mined that precious few remain in southern Wisconsin to tell us their story. The disappearance of these subglacial channels that once flowed beneath kilometers-thick ice sheets, thundering with heavy loads of boulders, gravel, and sand, demonstrates the immense power humans hold to act as a geologic force.
Bearing this in mind, Marcia leaves us with a parting message: We are all Earthlings, and being an Earthling means more than being human. Humans are not the only Earthlings—animals, plants, and rocks are Earthlings, too—and there are no boundaries between Earthlings; we are all united as cohabitants of our shared planet, with a shared lingua franca of the Earth. As Earthlings, we are each responsible for listening and seeing ourselves in relation to each other, and for acting with the knowledge that we are part of a system greater and more storied than ourselves, our species, and even our time.
Reading Rocks: A Primer
If you’ve had any introduction to geology, you’re probably familiar with the three main rock types: sedimentary, igneous, and metamorphic. Each carries memory in its own way.
Sedimentary rocks are deposited in layers directly through environmental processes. Each layer, or bed, is an integration of all the environmental conditions the sedimentary particles experience on their journey to their eventual bed—eroded from a rock, perhaps, into a smaller particle that tumbles down a hill into a river, where it is carried downstream until it’s deposited somewhere along the way along with countless other particles. In this way, sedimentary rocks have a near-continuous memory of past environmental change.
Igneous rocks hold more catastrophic memories. These rocks cool from molten magma, initially either erupted into Earth’s atmosphere (extrusive volcanics) or upwelled less violently into the planet’s crust (intrusive). Both forms express the composition of Earth’s interior, surfacing memories of what lies deep beneath our feet. While intrusive igneous rocks solidify slowly over time, petrifying memories of their cooling journey from the Earth’s mantle to its surface, extrusive volcanics cool almost instantaneously when they erupt into air or water, and record both their birth and Earth as it was in that moment of ossification.
Metamorphic rocks’ memories are perhaps the most complex. These rocks, plunged from the surface back into the Earth’s interior as the crust deforms (such as when tectonic plates collide), are then transformed into new rocks by heat and pressure beneath the surface. Metamorphic rocks have two stages of memory, the first at least partially rewritten by the second as if the rock formation were a planetary palimpsest or a poorly erased chalkboard. Looking at a metamorphic rock, we can read the story of both a distant past Earth and the rock’s more recent path from surface to depth and back, tracing a journey through the heat and pressure it encountered during its metamorphosis.
Earth’s geologic system miraculously preserves these myriad memories in ways we can access across the world.