[LINK] Marcia Bjornerud on the ancient beaches of Wisconsin

[rfmcdonald]

In her New Yorker essay "Meditations on an Ancient Beach", Marcia Bjornerud does a lovely job describing the genesis and the import of the Wisconsin Dells.

The billboards for water parks at the Wisconsin Dells begin at a radial distance of about two hundred miles, markers of the edge of an irresistible vortex into which most Midwestern parents will eventually find themselves drawn some blistering summer weekend. The place is a Vegas Strip for tweens, its resorts a shameless cultural and geographic mashup: Aloha Beach, Atlantis, Caribbean Club, Kalahari, Mount Olympus, Noah’s Ark. Which is why it can be startling to catch a glimpse—perhaps from the top of a three-story waterslide named for an Amazonian snake, out over the trespass-proof walls and crass façades—of the deep, winding pine-rimmed valley of the Wisconsin River and the honey-colored sandstones that are the Dells themselves. Some of the outcrops are undercut like anvils; others curve like the legs of a rococo table. The most recognizable is the mushroom-like Stand Rock, made famous by the nineteenth-century photographer H. H. Bennett, who captured an image of his son in mid-leap between an adjacent bluff and the formation’s flat summit.

The sandstones at the Dells can trace their beginnings to granites and gneisses of the southern Canadian Shield, a vast swath of rock that formed in the tectonic upheavals of the Precambrian, more than two billion years ago. Over the eons, erosion reduced the Midwestern mountains to sediment, and rivers, those compulsive custodians of the land’s surface, picked up the detritus. At the time the rocks at the Dells formed, five hundred million years ago, Wisconsin lay near the equator and was washed by shallow tropical seas. As the rivers meandered downhill and reached the shore, they jettisoned their sedimentary load in a systematic way, starting with the coarsest material—sand, which settled into beaches—and continuing with finer grains of silt and clay, which plumed out into open water. Wind and surf further sifted and rounded the grains. They became remarkably spherical and uniform in size. From the top of that slide, the machine-generated waves of the water park begin to look like an unintentional historical reënactment.