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Posts Tagged ‘sand’

BY TIMOTHY A. SCHULER

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Mapping the historic dunes hidden beneath the surface of Chicago.

FROM THE FEBRUARY 2017 ISSUE OF LANDSCAPE ARCHITECTURE MAGAZINE.

A few years ago, Mary Pat McGuire, ASLA, became fascinated by the South Side of Chicago—or rather, with what was beneath it. She was flying back to the East Coast often, leaving from Midway Airport, and she started to notice “really interesting patterns along the coastline that looked like stripes, ridges along the shore. They were some kind of remnant,” she says, describing the landscape south of the city. “I just started to wonder, ‘What’s really going on here? What was this place?’”

McGuire, an assistant professor of landscape architecture at the University of Illinois at Urbana-Champaign, was already familiar with the South Side’s more recent history of white flight, shuttered industry, and disinvestment. Now, she became interested in the area’s geologic history, and how it might be put to work. The landforms she spied from the air prompted McGuire to look at early soil maps made by the U.S. Geological Survey. What she found were (more…)

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BY PHILIP WALSH

A new cash crop is shifting the contours of Wisconsin's countryside.

A new cash crop is shifting the contours of Wisconsin’s countryside.

From the March 2015 issue of Landscape Architecture Magazine.

Two saucers full of sand sit on my desk. One contains a heathery mix of grains that I scooped up from L Street Beach in South Boston. It’s a blend of dark, light, and medium stone, mostly quartz weathered from the granite mountains of New Hampshire. Viewed at a distance it’s just gray. The coastal sands of southern New England were originally washed down by glacial floodwaters when the Laurentide Ice Sheet began to retreat about 20,000 years ago. Sand is dynamic, particularly when acted upon by the ocean. And indeed, the effect of water on stone is the very genesis of sand. The action of millennia of waves and currents reshapes the grains themselves. This sand is “semiangular”: The grains are irregular and somewhat sharp edged, although the occasional near sphere of transparent quartz does crop up now and again, as I peer at it through a 10x loupe. It is very young sand.

The second dish of sand is quite another matter. It’s an even golden color, reminiscent of straw or lightly done toast. The grains are on the whole much finer than the beach sand, and even without magnification they have a remarkable consistency, almost a silky quality. Under the loupe the grains are almost all rounded, most nearly spherical. The saucer also holds several large lumps of aggregated sand, still damp when I collected them at a mine operated by Fairmount Santrol at Menomonie, Wisconsin. This is sandstone from the Wonewoc Formation, and the mine was originally prospected by a nearby glassmaking company. Some of the sand from this site still ends up as windows. When I gathered these lumps of sand at the quarry, still moist, the stone had the consistency of halvah and readily crumbled into a heap of the distinctive, fine golden grains. Now that the sample has dried it behaves more like the sandstone it is. The Wonewoc sandstone dates to the early Cambrian Period, about 500 million years ago. It was smoothed into its typical roundness and sorted into beds by the actions of shallow seas that lapped the shores of supercontinents that predate even Pangaea, the breakup of which continues to shape our globe. This sand is so old that the tides that refined it were governed by a shorter day and a year 400 days long. It is unthinkably ancient.

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