top of page
Angled Chunks Flat.jpg

Stark and serene, the low sandstone coast west of Union Bay has drawn me more often than any other place around the lake outside of Minnesota. The bay sits at the eastern edge of Porcupine Mountains Wilderness State Park, or the Porkies as the place is often called, a nearly sixty thousand-acre preserve of forested hillsides with twenty-three miles of coastline near the southwestern base of the Keweenaw Peninsula. Tucked between forested hillsides and vast waters, the seven-mile stretch of coast between Union Bay and Buckshot Landing tells an epic story of ancient floods, droughts, and upheavals that fractured and upended the land. Mile after mile, it serves up a succession of cracked shelves, tilted outcrops, and shingle beaches, a world at once hauntingly tranquil and austere.

I set out from the campground in the bay a little after six-thirty one late July morning. The forecast calls for temperatures in the low eighties and barely a hint of a breeze, but with the air still cool and light the early morning sun comfortably warms my back. To the east of the bay storm waves and runoff have cut into the clayey bluffs that extend toward the mouth of the Union River while to the west a wide platform of brown sandstone moves north around a gradual bulge in the coast. Broad shelves angle up the shore, their vertical backs rising to two-and-half feet and sheltering scattered ninebarks, wild roses, harebells, and sedges. Jagged plates of broken rock rest on large slabs and at the edge of the forest a low ridge of shingles surrounds the trunks of aspen, mountain ash, and cedar.

Within a few hundred feet, the coastline narrows and softens along the water into smooth, claylike brown and lavender-tinted slabs and then tapers into a shallow cove lined with a steep slope of waterworn shingles. The slope is the first of many strips of loose stone that I’ll cross during my walk. While its base mostly consists of pebbles, its upper reaches are built from larger stones and plate-sized flats in assorted geometric shapes. Massive quantities of sandstone were crushed by the glaciers and shelves continue to break under the strain of storm waves, freezing and thawing waters, and heavy loads of winter ice. Cracked pieces end up swept into the lake, tumbled on the bottom, and pushed by heaving waves and ice into ridges on the shore.

From the slope’s crest, a thick bed of stones spreads inland across the forest floor before ending in a gathering of driftwood. Potted in red-brown shingles instead of a messy leaf litter, shrubs and saplings that I might otherwise overlook suddenly take on a new definition. Thimbleberries sport small clusters of ripening fruit that range in color from antique-white to pale pink and dark red, and a red-osier dogwood brightens the understory with what may be its final flush of white flowers for the season. Where the slope descends toward the cove’s far end, a stream flows out from under the stones while slightly inland a grove of black ash and sugar maple with a verdant carpet of lady fern fringes the purling waters. 

As I shift my gaze back toward the cove, a cedar waxwing takes off from a large boulder in the shallows. More cedar waxwings whistle from the forest and soon I turn to see several graceful birds with telltale black masks and peach-colored crests slipping in and out of the foliage. All day long, cedar waxwings will be my nearly constant companions, whistling and chirping a cheerful symphony in the broken-up shadows of the forest. 

Once past the small cove, the coast again widens into a low platform of sandstone that also includes large chunks and boulders of conglomerate. A long, broad area of mounded rock along the water helps break the force of waves, allowing mossy crevices on the inner platform to host young aspen, willow, and ninebark, harebell, goldenrod, and aster. Fleeting pools sometimes spread across the platform, but today I see only a single pool in a large dip with broken flats and water-logged mosses. On the lake’s southern shore, the bird’s eye primroses and butterworts that favor rock pools in Minnesota and Ontario mainly appear on the cooler and more exposed Keweenaw Peninsula to the north. The pool in front of me instead supports an attractive mix of rushes and sedges in muted hues of tan, saffron, yellow-green, and brown.

Like the rushes, sedges, and sandstone, the conglomerate boulders and mounded rock along the water tend toward a quiet blend of earthen tones where clean of lichen and stain. The long mound has a broad top and an unevenly dipping back embedded with a tight assortment of cobbles and pebbles, but fronts the lake with a smoother surface that only includes patches of stones. Among the clean stones on its back are a walnut-colored cobble with soft chisel-like marks, an olive-green oval with a shorn-off face, and a chestnut-brown crescent with cream-colored flecks, all surrounded by smaller pebbles, granules, and grainy fingers of cemented sand. Additional attractive stones in a soothing palette of warm hues create horizontal strings on low tails of rock along the water. Though I’ve come not even a quarter of a mile, I spend half an hour photographing the stones before hiking on. 

The coast between Union Bay and Buckshot Landing is the longest stretch I walk on the lake’s U.S. side. Save for a few rustic cabins hidden in the woods, it has no structures, trail markers, or other obvious signs of the human presence. Though I’ve walked the entire distance several times, I also often turn around halfway. Sometimes rough waters submerge shingle strips and narrow stretches of rock, requiring cumbersome detours into the forest. Other times leaden skies turn to rain or I stop frequently enough to photograph or simply sit around that I make too slow progress to both reach the landing and make it back to the campground by early evening. With the lake calm and sky clear, today I’ve decided to set a steady pace to make it all the way to landing, only to find myself already lingering by the cove.

Whether it consists of cracking sandstone, shingle slopes, or pebble- and cobble-infused ridges, the coastal strip presents a worn land of broken forms. The sandstone shelves fracture easily along vertical cracks and horizontal bedding planes, causing sheetlike one- to two-inch layers to peel off in pieces and leave behind uneven, angular surfaces with rough edges. As I’ll discover on continuing down the coast, wherever they appear, the thick cemented heaps of cobbles and pebbles create taller and more robust outcrops than do the sandstone shelves. Yet they built up from broken bits of stone and cobbles and pebbles, the majority of which eroded from the ancient Porcupine Mountains. 

Remnants of highlands of andesite, basalt, and rhyolite that erupted during the latter Midcontinent Rift period, the mountains rise inland of the lake to create three parallel ridges whose arc-like shape inspired Ojibwe to call the area Kaug Wudjoo or ‘place of the crouching porcupine.’1 The eroding ridges gradually shed sediments that laid down a formation of rock known as Copper Harbor Conglomerate, named after the town of Copper Harbor at the Keweenaw Peninsula’s tip. Reaching a thickness of up to five thousand feet in the Porcupine Mountains, the formation is also exposed along the coasts of both the central and upper peninsula.2 Rivers that coursed down the initially barren volcanic highlands dropped thick, cobble-laden bars on a vast alluvial plain where the mountains level out during times of heavy runoff.3 Yet as erosion took its course, the rivers began to carry fewer stones and instead mostly left behind sands and during times of low or waning water fine layers of mud or silt. Bed after bed accumulated and ended up compacted and cemented into thick stacks of sandstone. The rocks of the Porkies contain little true conglomerate.4 The stretch I walk mostly consists of pebble-free sandstone, but heavier runoff still sometimes dropped rubbles of stones, leaving behind cobble-infused slopes and ridges.

As I continue west, I soon see more evidence of conditions on the ancient floodplain in the form of a few broad wave ripples on a steep slope of rock. The ripples are covered in a lightly shimmering satiny glaze of lavender-brown mudstone with a few small chips that reveal the less polished brick-red sandstone underneath. Slightly further across the slope, the flattish surface instead glistens with parallel, diagonal streaks that shift between blue-gray, brown, and mauve, remains of silty sediments that washed across the floodplain. The streaks are rich in tiny, reflective micas and on a bright morning like this create a dazzling accent to the duller surrounding rock. 

The slope gradually descends to a low-lying point with a cabin in the woods, one of eighteen rustic structures for rent in the park. Harebells, buttercups, and balsam ragworts dot crevices on the upper rock, but my gaze soon fixates on several large patches of mud cracks, also known as desiccation cracks. The patches are evidence of a time when fine muds in pools that formed after flood waters receded or during stages of low-water flow dried out and cracked.5 When runoff later resumed, fresh water-borne sands settled in the cracks, sometimes creating striking mosaic-like patterns of varied sizes, hues, and textures. While I probably miss as many as I actually spot, by the time I reach Buckshot Landing I’ll have seen over a dozen intact mudcrack patterns and many more fragments on loose slabs.

When I first began visiting the lake, I had never heard of the Midcontinent Rift and knew little about the origins of volcanic, igneous, or sedimentary rocks. The Porkies coast rewarded me with far more generous clues to the land’s history than did its counterparts in Minnesota and Ontario. Except for in having hardened to stone, the mosaics bear a close resemblance to modern-day mud cracks, making their origins much easier to deduce than those of, say, a pillow lava or amygdule. The same could be said of the ripple marks, though maybe not the silty streaks. Deducing the origins of an outcrop of sandstone or conglomerate might require a bit more speculation, but the graininess and horizontal layering often visible in the former and the stones embedded in the latter would still provide more clues than could be easily found in an outcrop of granite or basalt. 

The largest mudcrack pattern around the point stretches to almost thirty feet, though it narrows to one end. Made of slightly angular, umber-brown pieces bounded by paler gray and red-brown cracks, it also includes a central area with light ripple marks, they too with cracks. I wander upslope toward a second pattern of mudcracks that disappears under a sturdy layer of overlying rock imprinted with astonishingly smooth, chocolate-brown squares separated by shallow grooves. In places, the surface of the squares has chipped to reveal thin, successive layers of mudstone, each not even one millimeter thick and creating a glaze that shifts between pearly white, pale peach, and mocha-brown. The layers easily flake off into fine slivers that lift into light currents of air and come to rest on the surrounding rock.

Most mud cracks that I’ll see during my walk span around three or four feet and have pieces that measure under two-and-a-half inches. The pieces often include a subtle mini-mosaic of thinner cracks or grooves and also come in a single dominant color, either brown, red-brown, maroon, burnt-orange, tan, or ivory depending on the extent to which their sediments were tinted by iron oxides. The more textured cracks, meanwhile, tend toward red-brown, gray, or clay-colored. The most striking patterns have glazed ivory pieces that have flaked off to reveal slivers of lavender or rose-tinted sandstone underneath. Even mud cracks that I’ve seen before often elicit a silent wow. Each mud crack offers a metaphor for an aesthetic in which beauty find its expression in the coming together of imperfect shards from a formerly parched patch of earth.

 

For the first mile and a half after leaving the bay, the coast lumbers steadily northwest, but eventually it dips lightly south and briefly levels out before settling into a gentle southwesterly trend. Though the rock occasionally widens, it mostly remains too narrow to provide much security for vegetation. Scattered flowers continue to lurk behind low shelves, and saplings of aspen, serviceberry, or birch sometimes bulge up from fissures in the upper rock. Here and there I even pass a creek or area of runoff with a light border of ferns, horsetails, and Canada anemones. Yellow sulphur butterflies flit in the sun as I seek the shady edge of the forest and bask in a sparing growth that appears luxuriant after a long stretch of bare rock.

Logging began in the Porkies in 1899 just west of Buckshot Landing at Lone Rock. During the next decade and a half, loggers cut over five thousand acres of white pine, cedar, basswood, and hemlock from the hillsides between Union Bay and the Carp River, five and a half miles to the west of Buckshot Landing.6 As often happened, fires later swept the cutover lands. The coastal forest had largely disappeared by 1916, but additional logging in other areas of the park staring in the 1930s eventually spurred efforts to gain protection for the area’s remaining old growth hardwood and eastern hemlock stands. The current park was established in 1945 and includes thirty-five thousand acres of old-growth sugar maple and hemlock forest, one of the largest tracts of this forest type in the United States west of the Adirondack Mountains.7 Giant trees blanket the rich, moist soils of inland slopes as well as valleys and ravines along the coast further west in the park. 

The lowlands along my walk, however, are dominated by second-growth forests, mostly of aspen, paper birch, maple, and fir with mixed stands also including white pine, cedar, yellow birch, and smaller amounts of hemlock. About three and half hours into my walk, I wander into the forest in search of a respite from the rising temperatures and unremitting sunshine of the open coast. A two to three-foot wave-cut bank separates the upper rock from a light stand of sugar maples that reaches back toward a hillside of hemlocks. Storm waves have scoured the earth free of duff and left patches of shingles up to a dozen feet behind the bank. No longer guided forward by the rocky strip, I loop inland between loose stones and black earth with meandering colonies of trout lily, wood anemone, wild leek, and fern. Eventually the duff reappears and is joined by light mosses and clusters of two-leaved toothwort, an herb in the Mustard family that produces white flowers in spring. 

Yet the vegetation soon diminishes again as the land rises toward the hemlock-studded hillside. I amble about in search of a log and sit down and pull out a well-worn, old edition of a book entitled Porcupine Mountains Companion by former park rangers and interpreters Michael Rafferty and Robert Sprague. Hemlocks, I read, are slow-growing trees that often live to be five hundreds years old.As they age, they gain stately trunks with dense canopies of feathery branches that keep sunlight from reaching the ground. While few herbs, shrubs, and other trees can tolerate the lack of light and acidic soils in their understory, clearings created by wind-downed trunks often become blanketed with saplings of sugar maple, an aggressive seed producer that shoots up quickly in the sun. Together, hemlock and sugar maple dominate the virgin forests of the Porkies.

Fittingly given the park’s name, according to my book, porcupines like to spend the long winters on the Upper Peninsula munching on twigs and inner bark of the two trees.9 The porcupines’ diet varies across the seasons, with spring in the park serving up aspen and maple buds, summer raspberry canes, leaves, and flowers, and fall acorns and nuts. Yet apparently, as I later learn, many porcupines loose their grip and fall from trees while reaching for buds at the thin ends of branches. Fortunately, their bodies are well buffered by a dense coat of quills, which even produces antibiotics to heal their impaled skin. I’ve sometimes seen porcupines in trees or lumbering across a trail, but have rarely taken much interest in them. What I read surprises me.

After fifteen minutes or so in the shade, pesky mosquitos disturb my peace and I put away my book and return to the open rock. At the end of the Midcontinent Rift period, the lands around the Porcupine Mountains crumpled up and fractured during a major episode of regional compression and faulting.10 The sandstone on which I walk was tilted to form the angled shelves and broken rows that dominate long stretches of the coast between the bay and landing. The angled shelves make for tough walking and already my feet are sore and my shirt soaked in sweat. As they rise out of the water onto the shore, the shelves create anywhere from one to three parallel broken-up rows with chipped upper edges that expose layers of underlying rock. In one place I make out a total of twelve layers ranging in thickness from one quarter of an inch to one and a half inch. Though mostly visible as fragments, some layers display solid gray or red-brown surfaces and others shimmering silty patches, wave ripples, or mud cracks. 

Elsewhere I pass rows of taller, steeper outcrops made of massive, upended chunks with backs that rise to five or six feet. Drawn to a faint movement at the base of an upended chunk, I startle a spotted sandpiper from a hidden nook. The bird takes off low over the water and soon turns into a blur of rapidly beating wings. Shortly thereafter, I come around a point and see a common merganser loafing with a brood on a low fin of rock in the water. I stop and slowly pull my binoculars from my pack, but have barely adjusted the focus before the hen makes a few clucks and one downy duckling after another slips into the water. The hen quickly follows and swims away from shore, sixteen ducklings settling into a single-file row behind her.

As I continue to wander fairly low on the rock, I eventually come across a slab with faint ripple marks covered in a scuffed satiny tan glaze. I first photographed the slab nearly twenty years ago, its smoothly glazed surface back then resembling a crisp topographical map with a bold design of continent-like ochre splotches with interior ridges and dark button-like islands. A few summers later I again photographed the slab. Yet when I chance upon it now I haven’t seen it in many years and have nearly forgotten about it. To my dismay, time has marked its passing on the surface of the slab as surely as on my aging skin. Extensive abrasion marks mar the formerly smooth glaze and the tidy map of continents and islands has faded, aggressively scoured by shingle-laden storm waves and ice floes.

The fine glaze had always been destined to wear away. Yet I instinctively want to preserve familiar areas of rock as I remember them, to hold on to the illusion that the shore exists as a stable, timeless place, impervious to the wear-and-tear, loss, and change that move across my own life. I stare long and hard at the ravaged design, the faded promise of its once clear map, and can barely force myself to take a final photograph. Were I to encounter the slab for the first time today, however, I probably wouldn’t see a washed out map but instead an abstract pattern with fine etch marks and curving daubs of lingering glaze. I wonder how many years will pass before I next see the slab, or if I’ll even recognize it when I do.

 

By late morning, I’ve begun to cross more areas where the rock slants at steeper angles and sometimes also grows more fractured, with myriads of small angular dips and corners that leave barely enough level ground to step on. With the sun by now blistering overhead, the air has turned oppressively hot and still and the walk has begun to feel relentless. The strip moves back and forth between solid and broken rock, with long strips of shingles separating stretches of angled sandstone. By the time I reach the landing, I’ll have crossed a total of nine shingle, boulder, or cobble strips, as well as several smaller areas of loose stone. Most strips are fairly level, but a few create steep ridges that surround the lower trunks of aspen and birch in full leaf. Sandstone dominates their stones, but smooth granites, basalts, and other rocks are also common. 

Many strips look discouragingly long when seen from their near end. But once I set out, the waterworn stones create a soothingly uniform surface for the eye. With little vegetation to speak of, they relieve me of my tendency to ceaselessly scan and stop to photograph or record. Occasionally I bend down over a cracked cobble with a finely banded interior, and once I nearly step on a garter snake that slithers out from a dip between two boulders. But mostly I move slowly forward while softly resting my gaze on the ground. By the time I return to the solid outcrops, my impatience has given way to a nearly meditative calm.

Much of my walk consists of moving between rocky points that shield the coast beyond from view, making it nearly impossible to tell how far I’ve come from the bay. But I know from past walks that a little over halfway to the landing the outcrops rise to a series of massive slopes that create welcome landmarks and places to rest. I begin to eagerly anticipate reaching the first slope and as I round point after point, my steps grow heavy at the sight of another shingle strip or long stretch of low shelves. Yet eventually I reach the first slope. The slope climbs steadily out of the water toward a hillside and then drops its vertical back into a patch of wild ginger and thimbleberry on the forest floor. As it rises upward, it gradually transitions from an uneven mix of short sandstone walls, dips, and slabs to a broad cobble-infused top with scattered cedar, jack pine, and white pine, and a mat of bearberries and wintergreens by which a fox has left scat.

I drop my pack in the shade of a pine and circle around. While the cobbled top gives the slope its stature and heft, the abundant walls and crevices further down on the rock harbor young serviceberries, a soapberry and patch of barren strawberry, and other low-growing vegetation. But even the more sheltered upper slope has the scrappy feel of a place wracked by fierce winds and storms. I soon return to my pack and sink onto the rock. A few long branches provide just the shade I’m looking for. As I pull out my lunch, the lake lies pearly and flat under the glare of the sun and a bald eagle soars out from over the forest, barely pumping its wings as it glides in a giant loop over the water and back toward land.

 

As I’ve been walking west, a long escarpment has gradually risen inland of the coastal plain, forming the northernmost of the three ridges that make up the Porcupine Mountains. The escarpment is made of sedimentary rock and capped by thin flows of basalt that briefly re-erupted from the Midcontinent Rift after much of the Copper Harbor Formation had already been laid down. Called the Lakeshore Traps, the basalt flows are inter-layered with sedimentary rocks that include pure metallic copper deposited in cracks and open spaces by hot, mineral-laden waters that were squeezed up from deeply buried volcanic rocks within the rift. More native copper ended up in the cavity-riddled tops of the older basalt flows and the interflow sedimentary rocks that underlie the Porcupine Mountains and extend in an arc up the Keweenaw Peninsula, where far larger copper deposits formed.11 These deposits contain the world’s largest source of native or pure metallic copper.

Possibly as early as seven thousand years ago, Indigenous peoples around the lake used  hammer stones, wooden pry bars, and fire to extract copper from pits in the ground.12 Over a thousand pits have been found on Michigan’s Isle Royale.13 More copper was gathered in chunks that had been loosened from the parent rock and dropped by the glaciers. From what I read in my Porcupine Mountains Companion, the soft native metal was heated and shaped into axes, spearpoints, ornaments, and other items, though the extent of early mining operations and possible trade-related activities isn’t well documented. French missionaries reported seeing pieces of copper on the lake bottom and in the hands of Indigenous peoples in the 1660s, confirming the rumors of earlier explorers about the metal’s presence. But aside from an unsuccessful venture in the 1770s, the first significant EuroAmerican mining operations didn’t begin until after the publication of Michigan state geologist Douglass Houghton’s 1841 report on the copper potential of the Keweenaw region.

 

The report set off the country’s first mining rush and in 1842 the U.S. government pressured local bands of Ojibwe to sign the first Treaty of La Pointe, which opened up the western Upper Peninsula to a stampede of miners and prospectors. For roughly four decades, profitable mining of larger masses of copper to the north and south of the park made Michigan the country’s leading copper producer. The Porkies, too, were divided into a patchwork of mining claims and dozens of small ventures were started on inland hillsides.14 Most, however, proved unprofitable. After breaking and hauling endless heaps of stone to the surface, the miners soon turned their backs on the shafts, trenches, camps, and even small towns they had built. Little mining took place along the coast, leaving the forests to my back to mainly conceal old tote roads and camps from the lumbering era.15

I finally put away my book, step back into the sun, and continue down the coast. The rocky strip continually remakes its character and just when it seems to become hopelessly fractured or uneven it levels out and gleams with the streaks of a silty patch or softens into claylike slabs with fine bands in delicate hues of ochre, rose, brown, or blue. Isolated collections of lavender, pink, and gray cobbles unexpectedly appear in the rock, as do weblike veins of white quartz or pale flakes of mud carried by water or wind.16 The latter crisscross an expansive area of exquisitely smooth, almond-brown rock that I soon reach after leaving the slope. Filling in myriads of thin cracks and inch-wide fissures, the quartz creates delicate webs, honeycomb-like hollows, and wedges that gleam in pale pink and peach. In thicker fissures, it surrounds angular fragments of orange-brown rock with a fine white lace, or forms larger white chunks embedded with shards of darker sandstone. The place feels full of ease and light, restoring my spirits in time for the next stretch of angled, fractured rock.

As I move closer to Buckshot Landing, I cross a long strip of shingles that extends for over three quarters of a mile. At its tallest, the strip rises sharply inland for up to thirty feet before ending in a crest of pebbles and driftwood and extending a two to three foot-thick bed of pebbles a full eighteen feet into the forest. I climb onto the crest as a cascade of clanking stones slip out from under me and turn to look back down the coast. Fathoming the volume of loose stones that makes up only this single strip is almost beyond my ability, let alone the immense quantities of broken rock that must rest on the lake bottom. 

Toward its far end, the slope nears a small point and descends to a more level strip of small boulders that encroaches on a pond abutting the forest. Pushed by waves and ice, the boulders have advanced inland and partly buried a cluster of dogwood and alder and left a few willow stems poking up like forlorn sprigs. To the west, more boulders cover the bottom of a channel of water that connects the lake to an inlet ringed by a tangle of uprooted trees. A sandpiper wades in the channel, holding its brown-spotted white chest an inch or so above the water as it dips its bill up and down. Since it doesn’t seem to mind my presence, I stop to watch it until it eventually steps out of the water and takes off for a downed log at the far side of the inlet, leaving me free to cross the channel on a narrow rim of boulders a few feet inland of the lake.

After picking my way between fallen trunks and outcrops, I finally reach the beach just east of Buckshot Landing. The landing, according to my Porcupine Mountains Companion, takes its name from a man named John “Buckshot” Miles, who apparently lived in the village of Ontonagon to the east and in the early 1900s had a cabin by the landing.17 A rental cabin for park visitors now sits in a clearing in a birch grove behind the beach. Having reached the end of my walk along the coast, I’ll soon turn inland to follow the Lake Superior trail for three miles out to the road, ascending a series of old cobble beaches and outcrops that mostly lie buried under the forest, and then continue downhill on the pavement back to the campground at Union Bay. 

Before leaving the coast, however, I wander a short distance west along the landing, a narrow inlet shielded by tall, angled outcrops. A shingle beach soon gives way to an alder-studded strip with a slender band of rock bounding the inlet. I wander toward the inlet’s far end, climb onto a hump of rock, and look down the coast at an airy mix of aspen and birch and a row of outcrops in the water. Two miles in the distance, marooned several hundreds of feet from shore, the tiny islet of Lone Rock punctuates the horizon with a pair of thick, angled backs. My face is burning from the sun and the long return walk back to the bay still lies ahead. But a part of me wants to keep threading my way toward Lone Rock, step by step taking in the upended rows and fractured slabs, the brokenness and stark contrasts that give the Porkies coast its captivating beauty and depth. 

__________

1. Michael Rafferty and Robert Sprague, The Last Porcupine Mountains Companion: The Story of Michigan’s Porcupine Mountains Wilderness State Park, 5th edition (Back to Nature Store, 2020), 9.

 

2. Robert C. Reed, “Porcupine Mountains Wilderness State Park, Michigan,” Geological Society of America Centennial Field Guide-North-Central Section, 1987, 2,  https://www.michigan.gov/-/media/Project/Websites/egle/Documents/Programs/OGMD/Catalog/05/GIMDL-GSA87B.PDF?rev=c4aa418d65ff43e499b341a5ca0d8375#:~:text=Rock%20formations%20of%20the%20Porcupine,principally%20from%20Hubbard%20(1975).

3. Rafferty and Sprague, The Last Porcupine Mountains, 38.

4. Laurel G. Woodruff, William F. Cannon, Suzanne W. Nicholson, Klaus J. Schulz, and Robert Wild, “Geology of the Keweenawan Supergroup, Porcupine Mountains, Ontonagon and Gogebic Counties, Michigan,” 59th Institute on Lake Superior Geology Proceedings, v. 59, Part 2. Field Trip Guidebook, edited by T.J. Bornhorst and R.J. Barron, 2013, 75.

5. Douglas R. Elmore, ”The Copper Harbor Conglomerate: A Late Precambrian Fining-Upward Alluvial Fan Sequence in Northern Michigan,” Geological Society of America Bulletin 95 (1984): 613.

6. Rafferty and Sprague, The Last Porcupine Mountains, 251.

7. “Porcupine Mountains,” Michigan Department of Natural Resources, accessed February 10, 2024, https://www.michigan.gov/dnr/places/natural-areas/porcupine-mountains.

8. Rafferty and Sprague, Porcupine Mountains Companion: Inside Michigan's Largest State Park, 3rd edition (White Pine: Nequaket Natural History Associates, 1995), 105.

9. Rafferty and Sprague, Porcupine Mountains Companion, 139.

10. Rafferty and Sprague, The Last Porcupine Mountains, 42-44.

11. “Michigan’s Copper Deposits and Mining,” Geography of Michigan and the Great Lakes Region, Michigan State University, accessed May 4, 2021, https://project.geo.msu.edu/geogmich/copper.html; Rafferty and Sprague, The Last Porcupine Mountains, 45-46.

12. “The Red Metal,” Porcupine Mountains Wilderness State Park, Visitor Center Display.

13. Greg Seitz, “Prehistoric Copper Mines and Long Human History Earns Isle Royale National Historic Designation,“ Quetico Superior Wilderness News, March 22, 2019.

14. Mines and Mining Locations, Map, Rafferty and Sprague, The Last Porcupine Mountains, 178.

15. Mines and Mining Locations, Map, Rafferty and Sprague, The Last Porcupine Mountains, 178.

 

16. Elmore, “The Copper Harbor Conglomerate,” 613.

17. Rafferty and Sprague, Porcupine Mountains Companion, 278.

bottom of page