Book Review: Great Lakes Rocks: 4 Billion Years of Geologic History in the Great Lakes Region
Great Lakes Rocks: 4 Billion Years of Geologic History in the Great Lakes Region
Stephen E. Kesler
I began Stephen E. Kesler’s Great Lakes Rocks: 4 Billion Years of Geologic History in the Great Lakes Region before I left for that area in late August and have, at the tail end of November, finally finished—not as slow as name your geologic process, but a good bit slower than it normally takes me to churn through 259 pages of text and notes. The pokey pace is no reflection on Kesler’s work but rather a twisted mirror image of life these last three months: weekdays filled with way too much work that accomplishes little beyond a paycheck, and weekends consumed by chores—including a large-scale project to order the chaos of the garage and transform boxes and bags of rocks and fossils sprawling indeterminately across shelving and floor into a thoughtfully sorted, labelled and stored collection that will allow me to once again park my truck inside for the winter—and the occasional day or field trip to provide a little spice to the usual gruel. Put another way, I’ve been busy, and so on this second day of a four-day Thanksgiving holiday, I found thirty minutes to polish off the last chapter of Kesler’s work and sit down at the keyboard.
Kesler is a professor emeritus of Earth and Environmental Sciences at the University of Michigan, and from the first page of the book, I found myself wishing I could have taken one of his classes. He has a gift for putting science in a human, temporal context, weaving it into both history and geography to explicate how geological processes result in mountains and lakes, rivers and plains, oceans and continents and how the rocks and minerals that compose these mega-features alternately shaped and were shaped by their evolution. Like many other geology books, this one covers the full sweep of Earth’s history, but by narrowing his focus to the Great Lakes region, Kesler finds the space to home in on the specific events within the broader story that explain local features such as fossils in Michigan, banded iron formations in Minnesota, glacial gravels in Wisconsin, and the depth and breadth of the eponymous lakes themselves.
The arrow of time moves resolutely forward, and we are riders on the very tip of that point where now meets not yet, our vision of the moment as clear as circumstance and comprehension allow, what has come before possible only in the light of what is so long as we are guided by the principle of cause and effect and not the improbable magic of miracle and make believe. When the end point of a story is known and continuity required for its telling, the author may start either with the known and work backward to account for this ending or with some earlier point that unfolds to yield the current end. Kessler chooses the former path, starting from the present and declaring in the first subheading of his second chapter that “Surface Features Reflect the Underlying Geology” (15). And so we move from surface to the geological subtext that has created the view from our windows today: the retreat of the last glacial ice sheet that covered much of the Great Lakes region during the Pleistocene, leaving behind the multiplicity of lakes and wetlands that dot Ontario, Manitoba, Wisconsin, Minnesota and Michigan. The chapter is entitled “Landscaping the Continent,” and beyond describing the geophysical processes of glacial retreat that pitted the earth and filled in these pits with melting water, Kessler notes the effects of human “landscaping” as well, citing the changes our species have made—from potentially hunting species to extinction to definitively polluting the waters and destroying vast swathes of habitat via mining, farming and other activities—and cautioning against potential ends that await if we lack the will to trace consequence to cause and act accordingly.
Throughout the six following chapters, nature in the form of physics, chemistry and biology takes center stage, contemporary humans appearing as a sort of geological Greek chorus teasing out and commenting on the action as we move back toward the very beginning of the planet. With the exception of the first chapter, all of Kessler’s chapter titles begin with a present participle, and thus we move from freezing (in the Pleistocene) to flooding (in the Mesozoic and Paleozoic) to rifting (in the Mesoproterozoic) to building (in the Paleoproterozoic) the North American continent to making the craton (in the Archean) at the heart of the continent to making the crust (in the Hadean) that comprises that craton. As with all geological timelines, there are gaps and educated guesses about why those gaps are present and what might have happened within them, but here the narrowing of scope from the entire planet to a particular region provides a simulacrum of continuity—especially since so much of this history has been or is currently being studied by a host of scientists tracing everything from the depth and length of Mesozoic and Paleozoic coal seams to the Paleoproterozoic meteor impact that generated the Sudbury igneous complex to the U-Pb isotopic analysis of Archean zircons in Minnesota gneiss. Geological study of the Great Lakes region is clearly a vibrant pursuit, and Kesler has a certain grasp of the players in the field and their findings.
The text is fairly friendly to a lay reader, but Kesler does not steer clear of complicated topics that must be addressed in order to explain the findings. The book is not a graduate-level text by any means, but neither is it the field identification guide its title suggests: you will find some pictures of rocks, but if you’re looking for sexy shots of some sweet Lake Superior agates or something to help you distinguish between diabase and gabbro, this ain’t the book for you. (If your proclivities/needs fall into either of the aforementioned camps, I suggest you try either Lake Superior Agates Field Guide and/or Lake Superior Rocks and Minerals Field Guide, both by Dan R. and Bob Lynch.) As is, sadly, often the case with geology books, photos are generally in black and white, and even in the “special” color section, they are printed on matte paper and not gloss, so the quality is middling. The quality of the diagrams Kesler includes, however, is far higher. These are the pictures that are worth a thousand words in helping the reader envision and understand how past events are embodied in the region’s rocks and landscapes.
The final chapter of the book, “Sustaining the Continent,” discusses the future geology of the Great Lakes region. Earlier this year, I stared down yet another future-facing end chapter of another work and wondered if I would ever read a science book from the 21st century that didn’t conclude with a dire warning about unchecked climate change and the end of the world as I know it until it occurred to me that of course I wouldn’t. Science draws hypotheses from observation and tests those hypotheses to measure effects generated by causes. Ideally, this measurement is the result of experiments in which the initial state at the start of the experiment is known and specific changes to that state are induced by the experimenter in such a manner that variances in specific parameters can be tied to specific outcomes. The world, however, is not such a laboratory. We began an experiment without knowing the world’s initial state—without, in fact, even the awareness that we were launching an experiment upon it. We have been just stumbling around imperfectly living our lives in some strange state of conscience in which we are at once small and inconsequential compared to the vastness of our home and mighty masters who can bend nature as we will. The future cannot be known until it is the present, but just as the present it contingent on the past, the future is contingent on the present. Kelser ends by noting that, as a species, “we will likely persist” (258). Whether that persistence is thriving or surviving remains to be seen.