Fluid earth and glacial forms—clay slides, lava flows, sheets and caps of ice, glacial drift—extend themselves from time to time in rounded, tonguelike projections called lobes, sometimes vast in scale. Lobes of the great Pleistocene ice sheet, such as the Des Moines Lobe and the Green Bay Lobe, extended for hundreds of miles, leaving lobate moraines— curvilinear hills that snake across the landscape, marking the terminus of the ice and pauses in its position as the glaciers melted back thousands of years ago. Henry Thoreau, in Walden, riffs grandly on much smaller examples. Observing the forms assumed by thawing sand and clay in a raw railroad cut, he finds “moist, thick lobes” suggestive of internal organs verging into leaves, feathers, and wings of “the airy and fluttering butterfly.” “The very globe continually transcends and translates itself, and becomes winged in its orbit,” he exults, and concludes: “There is nothing inorganic.”

John Daniel