For Love of Lakes

Agassiz’s Gift

· · 36 · · Agassiz’s Gift Therealvoyageofdiscoveryconsistsnotinseekingnew landscapes,butinhavingneweyes. MARCEL PROUST Five hours after leaving home I turn off the highway onto a county road and drive for one mile to where the road tees. I pull the car onto the shoulder and open my map to get my bearings. I am searching for a ghost lake, a lake that no longer exists. Perhaps, in some subconscious way, my childhood fascination with a storybook tale of a boy who swallowed the sea, so his people could walk unhindered over the sea floor to gather fish for food, explain why I am here. How exciting, I thought, to walk the bottom of a lake. What strange new things one might see. • • • A great valley several miles wide cuts a broad swath through the corn and soybean country of south-central Minnesota, slashing south then east from the state’s western border for 300 miles. Its line runs remarkably straight, as though whatever created it had serious intentions. My family moved to a small town on the floor of that trough when I was six. On move-in day, as my parents carried our few belongings into the north side of the white · · 37 · · duplexthatwastobeourhome,Ibecamefascinatedbytheblufflineofhuge hills that dominated the landscape along the north edge of town. Steep ravines separated the hills. A gravel road climbed one ravine to flat farmland above. Morton Creek arose out of another, its waters eventually reaching the chocolate flow of the Minnesota River at the edge of town. The Minnesota at Morton is not a large river. I once watched a man wade across in hip boots. The river wanders aimlessly through farmland in a ludicrously oversized valley, as though it is lost. The town sits at the edge of a bedrock platform protruding above the valley floor. A knoll of bedrock extends the school playground into a rolling terrain of rounded rock knobs. I did not understand then, nor when we moved away seven years later, that the immense valley in which we lived spoke of momentous events of the past. I could not know then that, but for a gigantic lake farther up the great valley, there would have been neither exposed bedrock nor steep hills on which to scramble. Lake Agassiz, named for a bright Swiss natural history professor, extended north from the head of this valley at the Minnesota–South Dakota border nearly a thousand miles to northern Saskatchewan and six hundred miles northeast into Ontario. Although its shoreline changed over time, Lake Agassiz is the largest lake to have existed in North America. This great lake, in its time, covered an area four times the size of present-day Lake Superior, the largest existing freshwater lake in the world. Lake Agassiz is no more, though large lakes in Manitoba and northern Minnesota occupying its deepest depressions remain as reminders of the great lake’s expansive past. • • • My second association with the ghost lake came when we later moved out onto Agassiz’s former bottom in northwestern Minnesota, where, as Laurie Allman has written, “The landscape is level enough that caterpillars crawling across the road stand out as topographic relief.” I must have heard of the lake by then, but sense it, feel it, believe it? How can you see lake when your eyes tell you of towns and fields of corn, sugar beets, flax, and sunflowers? • • • agassiz’s gift landscapes· · 38 · · I have come to discover the great lake for the first time, to establish a perceptual relationship with a ghost. I cannot touch its water, nor watch its whitecapsroll,norhearthemsmashagainsttheshore.Icannotsniffitssmell and I cannot taste its sweet waters. Can one experience such a lake? Louis Agassiz, the lake’s namesake, once tried to establish such a relationship with a ghost. His ghost was not a lake but a thick sheet of ice. On July 24, 1837, this brash up-and-coming scientist jolted the scientific world. He set aside his planned address on fossil fishes and laid before the gathered naturalists of the Swiss Natural History Society an audacious idea. Thick sheets of ice of continental proportions had once moved across the land, he said. Glaciers had sculpted the landscape. Nonsense, chorused fellow scientists as word of his claim spread. William Buckland, prominent English geologist, had launched a fullscale investigation early in the 1800s to explain how landscapes came to be. At the outset, like most scientists of his day, Buckland had no doubt that the catastrophic biblical flood had...