* This week “Problematica” visits the oldest intact surface rocks in the United States— the Morton gneiss (pronounced “nice”) in Morton, Minnesota. Misadventure ensues. All the photos in this post are from my trip unless otherwise indicated. Problematica is written by Max Dresow…
To see the oldest intact surface rocks in the United States, first park up the road from the Morton Inn. Don’t bother looking for a sign or commemorative plaque: you won’t find one. Instead, just walk up the hill.
What you see when you arrive at the Morton Outcrops Scientific and Natural Area in Morton, MN
If you’re like me you'll be wearing old running shorts and flip flops. Don’t be like me. The hill you need to climb is thick with tallgrass and scruff, a ragged patchwork of prairie natives and hardy invaders. Indian grass dominates the first hundred feet or so. That’s easy enough to tramp through, and you might even find yourself thinking that your shorts-and-sandals combo is alright. Still, you feel a pang of regret.
The way up. The sign on the hill says nothing about the gneiss. It simply indicates that this is a protected natural area and lists rules of conduct
You walk on. Butterfly weed grows here and there, providing splashes of orange amid the ochre. Prairie clover waves above the ripple of grass, happy and purple. The commonest wildflower is Canada goldenrod, a bushy little perennial that belongs to the same family as the sunflower. Its clusters look festive and sag under their weight. Then there is leadplant, heath aster, purple coneflower. Yellow, purple, orange— the prairie has a reputation for monotony, but that’s only in wide-angled contemplation. Zoom in and it’s decked in as many colors as you like, and stunning in its variety. It’s a shame there’s so little of it left.
A purple coneflower (left) and butterfly weed (right)
Further up the hill your troubles begin. Here the wildflowers thin out and nestle into the shade of more assertive (and, it has to be said, less attractive) plants. I don’t know their names but they’re green and sharp and look like invaders. Your ankles begin to take a beating.
Then you see it. Pink and gray with laminated swirls and little white flecks. This is the Morton gneiss, peeking out from the hillside like flesh smiling from a wound. You tell your son that it’s over three-and-a-half billion years old: a high-grade metamorphic rock squeezed to the surface about 100 million years ago. He's two and doesn't care. Your wife, who is holding your 10 month old, says she can’t go any further. She wishes you luck and returns to the car, while you push on through the tangle, now holding the two year old against your chest.
At last you near the top. The shivering of grass announces the presence of a chipmunk, or maybe a snake. You curl your toes. Then, further up the path, a beer bottle. Teenagers have been here too. With a little hop you mount the ridge and look around. Atop the hill gneiss is everywhere, forming an inconsistent pavement. A small promontory commands a view of the Morton Inn and, beyond it, Highway 19. This is gneiss too. Surprisingly there is a new plant community, forming what ecologists call a “Crystalline Bedrock Outcrop Prairie.” Rock spikemoss, little barley, and California geranium all flourish amid the bedrock. And within the rock, ephemeral pools support flattened spikerush and Carolina foxtail. Some of the depressions are little potholes that formed in torrents of water not so long ago, geologically speaking. They seem beneath the dignity of a rock so cosmically old. But you suspect that to a rock, any erosion is a kind of indignity.
The rock on which you’re standing is a composite of quartz, feldspar, biotite, and amphibole. It formed more than three-and-a-half billion years ago when molten material cooled to form granite deep in the belly of the Earth.* Later, this granite was caught in the vice of plate tectonics, re-melting it so that pink feldspar could wind its way into the fabric. Gradually it hardened only to heat up again, adding still more colors to the swirl. Then, about 100 million years ago, it was squeezed to the surface. The dinosaurs flourished, the dinosaurs died. Newly confident mammals pawed at the rock. Then, ice. Glaciers flowed back and forth at intervals across the future northern states, covering the gneiss in glacial sediments. Finally, about 12,000 years ago, Lake Agassiz burst, unleashing a massive bulldozer called the Glacial River Warren. This cut a deep gorge through what is now the Minnesota River Valley, removing the sedimentary apron, exposing the gneiss, and making those damned potholes.
[* Individual zircon crystals from the gneiss have been dated to 3,524 ± 9 Ma. This makes the gneiss not only the oldest intact surface rock in the United States, but one of the oldest rocks on the planet. The oldest intact surface rocks on the planet are closer to 3.8 billion years, although some studies claim older ages for rocks in the Canadian Shield.]
You try to remember all this as your son does a happy little dance. But really only one detail matters. 3,500,000,000. The Morton gneiss is over three-and-a-half billion years old. That is about the age of the very oldest fossils, and is definitely on the list of the most impressive things about Morton. So why does it feel like the rocks are basically hidden?
* * *
In Morton, the grass grows through the sidewalk cracks. An old tractor wheels heavily through town. A hybrid sedan glides by without stopping. Very few sounds disturb the monotony of the afternoon. There are 400 souls here, but I don’t see a single one. Perhaps they’re sheltering from the heat, or else working in one of the buildings adorned with gneiss from the quarry. Anyway, no one is outside, and certainly no one is bushwhacking their way up the hill behind the inn.
The abandoned Morton high school building near the outcrops. Notice the gneiss on the facade (photo from internet)
The first thing you notice when you arrive in Morton is the sign. It’s made of a slab of polished gneiss and would do credit to a settlement much larger than this one. (It’s a really nice sign.) Apparently the people of Morton are proud of their gneiss. I’ve since learned that it’s been quarried since 1884 (the year the town was incorporated) and that it adorns such buildings as the Adler Planetarium in Chicago and the Zion Lutheran Church right here in Morton. It’s also on the liquor store. Morton is literally the town gneiss built. But then why are the outcrops so anonymous? An unhappy thought springs to mind. Perhaps the people of Morton don’t believe that the rocks are over three-and-a-half billion years old— this is rural Minnesota, after all. Or maybe they just don’t care. Anyway, I’m taken aback. The world’s biggest twine ball has its own gazebo and yearly celebration in nearby Darwin. Shouldn’t the oldest surface rocks in the United States have a sign and proper walking path?*
[* There is a sign in Granite Falls where the gneiss also outcrops.]
Two buildings clad in Morton gneiss: Morton Liquor and Adler Planetarium (photos from internet)
When we get home I call my dad. I realized as I drove that Morton is not too far from his hometown of Wabasso, Minnesota. I started wondering if he knew about the town, and perhaps even the gneiss. He didn’t know about the gneiss, but I learn that he once crashed a motorcycle not a hundred yards from the outcrops. (Dad evidently got his motorcycle certification in the parking lot of the now-abandoned Morton High, near the inn.) He also tells me that his grandmother, Annie Dresow, lived in Morton for a number of years near the end of her life. Dad used to visit her during summers and enjoyed climbing on her giant retaining wall. He even drove through Morton a few years ago to see how things had changed. Evidently they hadn’t changed much, although the retaining wall was smaller than he remembered. Time has its way with things, if not through slips of memory then through hard wind and heavy rain. I think of the gneiss, anonymously eroding as cars and tractors roll past on Highway 19. I wish drivers knew it was up there. But I suppose it doesn’t make much difference either way.
The stones on that hill are mind-bendingly old. They are also mundane— just a huddle of rocks covered in lichen the color of bathroom tile. Some plants favor the gneisses, and a whole mess of birds seem to enjoy shitting on them. But except for a few geology buffs the Morton gneiss is not a valued part of Minnesota’s natural heritage. I feel indignation pressing against resignation. What is the value— the real value— of some old rocks? And why do I, as a Minnesotan, feel a flicker of pride that they lie within the boundaries of my state? Probably I’ll never visit them again. Maybe I won’t even recommend it. Still, I’m glad I made the trip.
Time has a fascination of its own, independent of the stuff that fills it up. I could intellectualize this, but I won’t. Anyone who has marveled at the night sky understands the feeling: an inarticulate reverence for enormity, a wild yelp in the darkness. You weary at the prospect of expressing the feeling in words. But to express it in words would debase it, so you don’t try.
References
Minnesota DNR: “Morton Outcrops SNA.” https://www.dnr.state.mn.us/snas/detail.html?id=sna02051
More on the Morton gneiss: https://kirkby.esci.umn.edu/displays/basement-atrium/morton-gneiss
“The Most Beautiful Building Stone in the Country”: https://geologywriter.com/streetsmartnaturalist/stories-in-stone-blog/the-most-beautiful-building-stone-in-the-country/