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       The team we gathered to build our timber frame house was a group of artists working construction day jobs, and when it came to setting our stone foundation, they all agreed Tom should take the lead. A lanky guy with a graying ponytail, Tom carried a dog-eared copy of Living the Good Life with him everywhere. Helen and Scott Nearing’s self-published 1954 chronicle of their move to rural Maine has been the bedrock for many a back-to-the-land journey, and includes a how-to guide for building a strong, straight stone wall.

       Doug and I were feeling our way toward building the greenest house we could—both a home and laboratory of sustainable shelter ideas with a carbon footprint the size of a baby’s bootie. That meant passive solar design, and locally sourced, natural materials. We were inspired by the generations-old limestone foundations of faded red barns along our country road.

       Thirty years earlier, during Doug’s postdoc in the Netherlands, we lucked into renting a 300-year-old farmer’s cottage along the edge of what was originally a Roman road. It stretched our sense of what a house could be to include axe-hewn timbers supporting wattle-and-daub walls and a thatched roof. We ate our meals, tucked our daughter into bed, and dreamed through the long winter nights in a structure that has sheltered families for centuries. So when it came to constructing our own house, no envelope-pushing idea seemed like a bridge too far. We were determined to lay the foundation for a home that might last as long as that Dutch cottage.

       The land that the Nearings went back to was rich in a hard, igneous rock created some 400 million years ago when magma cooled and solidified deep underground. Our own rock is somewhat softer—soft being a relative term if you drop a chunk on your foot. Our bedrock was formed about 500 million years ago when Wisconsin lay near the equator beneath a warm, shallow sea teeming with creatures whose shells drifted to the ocean floor, bonding with quartz sand, and compressed over eons.

       We paid a visit to Swiggum Quarry about ten miles away. Some of their limestone was broken into pieces of about the right size, and they glowed a pleasing, yellowish tan on that sunny morning. I was totally on board when I realized this kind of rock can be chock full of fossils— especially trilobites—that flourished into thousands of shapes and sizes, from three inches to three feet, in that ancient sea. Primeval precursors of insects and crustaceans with a pleasing pattern of triple ridges down their backs, trilobites grew by molting—each little fellow leaving a series of exquisite exoskeletons in its wake.
       Wisconsin’s state fossil, the Calymene celebra, was an adorable little trilobite scavenger who could have fit into the palm of your hand. If they were around today, you might keep a few scuttling across the bottom of your aquarium. Good luck catching him before he burrows under the sand!

       Peter Brannen, in The Ends of the World, dubbed trilobites the standard bearer for the Paleozoic era. They survived the End Ordovician mass extinction 444 million years ago, and the Late Devonian 360 million years ago, but burrowing could not save them from the End-Permian Mass Extinction about 250 million years ago. Called the Great Dying, 96 percent of all species then alive were wiped out of existence. Intense volcanic activity in Siberia threw sulfur and CO2 into the atmosphere, causing brutal global warming and acid rain [1].

       Trilobites that had scurried across the sea floor for 300 million years were suddenly slime, along with those who had crawled onto land and evolved into reptiles—some as big as the dump truck that delivered our stone. By the end of the Permian, nearly all of them had perished [2].

       The world in which trilobites thrived is long gone, but their fossils show up around here in places where roadbeds have been cut through the hills. Some of the richest roadside fossil viewing in our state is just minutes away from our land. We’d ordered a truck full of rocks and received a treasure trove of relics in the bargain.

       Tom was not pleased with the quality of our rock when he saw the pile next to our house site. We belatedly learned that the rock from Swiggum Quarry is not generally considered attractive enough for building or landscaping and is usually crushed for roadbeds.

       O.K. So our stone was not ideal, but when you’re building a house with a sod roof, you are already (apologies to R. Frost) far down the path off-the-path of the path less traveled by. We forged ahead, helping Tom set up plywood forms and began to set stone knee walls that were basically straight and definitely strong.

       Each stone was contemplated, then pivoted to fit its flattest side against the frame, more or less snugly next to its siblings. We shoveled concrete into the gaps, and let it set up before pulling away the forms and moving them on to the next section of wall. Because our stone was not as flat and smooth as Tom would have wished, concrete often oozed and hardened between the rock faces and the plywood. Every day of fitting stone was followed by two days of chipping concrete. The perfect tool for this dirty job turned out to be some of the smaller chunks from our rock pile.

       Squatting in front of our growing wall, pounding away errant concrete globs, I felt as close as I’ve ever been to prehistoric humans who hollowed out canoes and shaped their own shelters with a rock in hand, though honestly, for someone with a cell phone in her hip pocket, it got a bit tedious. Bang upon endless bang. Each impact transferred through the bones in my hand and resonated up my arm. An hour of chipping felt like an epoch, but the wall slowly took shape, and the rock pile shrank.
       We had almost enough rocks for the job, but Tom and I eventually had to take his rusty pickup back to the quarry to find the best stones we could for the final push. Rick, the quarry man on duty, weighed our empty truck at the entrance and warned us to work fast because they were setting up to blast deeper into the rock face that day.
       We wound our way through the lifeless, lunar landscape till we found a pile that looked promising and were picking through it for usable chunks when Rick roared up in a gigantic dump truck. Time to get out of the quarry. Now!
       Dropping the rocks we were holding, we hopped into Tom’s truck and raced after him to where Jerry, one of the explosives technicians, was waiting at the entrance. He phoned his partner. Three warning honks reverberated, then a crack like doom shook the valley.

     Jerry told me he blows something up just about every day. Swiggum Quarry, he said, gets “shot” about twice a year. He grinned when I asked him if his partner had plunged a handle to detonate that mayhem. Explosions these days, I learned, were triggered by a hand-held device with two yellow buttons and a red light.
     No sticks of TNT either. Acetic acid, the main ingredient in his explosives, was transported by tanker trucks. Jerry and his partner always mixed the explosives on site, so as not to be driving around with a volatile load that could come to a bad end on a train track or in a highway pileup.
     Before the dust drifted away, Tom and I rushed straight for the new blast site. My nerves were still jingling from the explosion, but I was excited at the prospect of fresh rock. Local and fresh? How good can roadbed rock get?
     As we approached the avalanche, Tom looked at me with a raised eyebrow. We were both struck by a distinctly pungent smell. I stopped and closed my eyes. I knew that smell, though I had never smelled it in Wisconsin. Could we be inhaling the long- trapped scent of an ancient ocean? I filled my lungs deeply and held it as long as I could.
     That overpowering sense of sea breeze dissipated quickly as we searched, and soon we were sweating in the same hot, dusty air we had been breathing before the blast. We loaded the pickup with enough rock to finish our foundation, got weighed again, paid 12 dollars, and left.
     The next few days, as I mindfully fitted those rocks into the last of the wooden forms, I found myself inhaling hopefully as I hefted each stone, dreaming about that long-lost sea bottom under my feet.
     Later that week I called up Richard Slaughter, the Director of the University of Wisconsin-Madison Geology Museum, who maintained that I could not have been inhaling odors of an ancient ocean. Though Paleozoic seas might well have smelled a bit like their modern counterparts, I was assured that any such smell in our limestone had been washed away by millions of years of fresh groundwater.
     Still, ten years later, when I look at our sturdy, fossil-studded foundation, I believe that I did once inhale the last breeze of a lost world where trilobites scuttled freely across a warm and friendly ocean floor, as if they could go on forever.

[1]Brannen, Peter. The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth’s Past Mass Extinctions. New York, NY: Ecco Press, 2017.

[2] Ibid.

A science writer focusing for the past 15 years on environmental issues, DENISE THORNTON currently writes for The Aldo Leopold Foundation and has a blog (www. Denise and her partner pour themselves into prairie and woodland restoration on their 44 acres in the Driftless Area of Wisconsin, where they live cozily and with clear consciences in the branching, unmilled timber frame, straw bale, passive solar, sod roofed house referred to in her essay.

ETHAN LAHM attended the University of Colorado Boulder as a Senior earning his Arts Practices BFA when he submitted his work to Changing Skies. In his free time, he enjoys drawing, painting, petting dogs, and exploring the Boulder area. Ethan also hopes to make comic books one day!

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