The Last Word On Nothing

My husband and I went to Scotland to celebrate our 25^th wedding anniversary. We walked on footpaths in the Highlands and noticed all the ways the landscape  differed from our favorite hiking trails in New York.  My naturalist skills extend to birds and plants. It was hard to ignore the rocks, but I did my best.

I could handle the random boulders, likely erratics left alone in a field by a retreating glacier. I can go 14 thousand years back. But geologic time? It’s overwhelming. Except that time I reported on some fossils from the Devonian period. Evidence of Earth’s oldest trees were discovered near Gilboa, New York, less than an hour’s drive from my home. I loved reporting the story and I came out with a toehold in geology.

Later in our trip, on the Isle of Arran, we happened upon the Arran Heritage Museum in Brodick. The eclectic collection included a wall with Highlander weaponry, a corner with various lichens used to dye tartan colors, and a whole room devoted to geology. I entered tentatively and scanned the first panel, knowing that I could turn around and walk out — or skip ahead to the Devonian, where I could surely comfort myself looking at fossils, such as the cute and stripey trilobites. The displays, organized on a geologic timeline, included text and pictures on the walls and rocks in glass cases below. I meandered along, vaguely looking at descriptions of rock types and earthly forces. I felt overloaded and yet, I kept scanning, essentially looking for a new toehold. I found it on the next wall, where I read about rising magmas — which we would call lava had they pushed up through the Earth’s surface.

In Scotland, the magma didn’t break the surface in the Tertiary period, but erosion has laid them bare for us to see today. Tertiary igneous dykes. I voiced the term and repeated it like a mantra. I pointed John to the description, again practicing the moniker. A brute force method of remembering a foreign-to-me phrase.

The next day we explored some walks recommended by our B&B hosts. First we tiptoed around sheep droppings to get to the stone circles of Machrie Moor in the rain. Next we walked through some woods to the beaches on the south shore of the island. The sun was out and we prowled the rocks at the water’s edge. We spied limpets and barnacles and discussed commercial uses of seaweed. I strolled on the beach toward a distance set of rocks. That’s when I noticed the rock formations that appeared as jetties,  weirdly black, weirdly smooth, and seemingly one mass.

Lightbulb moment: Tertiary igneous dykes!

Over breakfast the next day, our B&B host, a trained geologist, told us about a famous geologic structure on the island — Hutton’s unconformity.  I love the feel of a new-to-me word — unconformity — so I listened. Near the tiny village of Lochranza, James Hutton, a British geologist noticed an unusual feature:  a set of rock formations atop a different set of rock formations. Essentially, one layer of rock formed and then experienced an uneven uplift (it is angled relative to the ground). Another layer of material was laid and hardened (Cooked? Pressed? Parboiled? I don’t know this stuff!) into its rock formation, horizontally, on top of the first layer. To Hutton, this sandwich of features indicated multiple protracted periods of time. He used the unconformity to argue that the Earth was much older than the Bible would have it — millions of years, not thousands.

Intrigued, we studied our map as our host showed us where to find the unconformity on a map.

Yet another footpath on yet another day threatening rain. We walked towards the rocky beach of Hutton’s discovery. We walked and looked. I remembered our B&B hostess warning us: “It’s very easy to overlook. Even when you’re looking right at it, it’s not that obvious.” John remembered the photo our host had showed us, where it looked really obvious. I wasn’t certain that photo was from this spot. (After Arran, Hutton found other, more obvious and instructive unconformities on other Scottish shorelines.) I recalled our host saying that it was easier to see from a boat, which had me scrambling over wet rocks next to the lapping waves. John stayed on the path, certain we should be looking at the bluffs set back from the shoreline.

We walked and looked some more. We were sure we’d passed the spot, but we continued on the footpath that led us along the coast. We climbed up the hillside for a better view of the water, we built cairns with beach rocks, and we ate our pack lunch. Then we retraced our steps and recommitted our efforts to look for the unconformity. Which means we reiterated our stances — near the water vs on the bluffs, practically undetectable vs fairly obvious. Ah, marriage.

In one spot the rocks were clearly different. Some indeterminate rocks at ground level, with red sandstone perched on top. (You see how easily I slipped in the red sandstone? That’s an easy one for a nongeologist.) The top layer of all the large formations were black. The color contrast was plain to see, however we weren’t supposed to be looking for color shifts.

We were looking for angles. Picture me, standing atop a shelf of rock. It’s easy to imagine how that structure was lifted at an angle from deeper down in the Earth. The striations on the rock sides match the angle of the lift. I’m looking westward, with my right arm bent to match the angle, low toward the sea, high towards the land. I move my left arm to take an opposing angle and my eyes scan the shoreline for a match.

Maybe there? Hmm. There? I’m not sure.

I called to John to explain what I’m doing, what I’m seeing. He’d become transfixed by the red sandstone layer I’d noticed earlier. He was trying to make it fit what we were told.

We continued our search, setting out separately and coming together to debrief. We agreed that even if we didn’t find the unconformity, we have enjoyed the search. And I realized: I’ve spent the last hour studying rocks like I never have before. I would stare at a jutting ledge and try to conjure up some story of its formation.

We spotted an older couple watching us. It turned out, they were looking for Hutton’s unconformity too. We compared notes — or, more precisely, the mishmash of what we think we’re looking for, what we remembered from what we’ve been told.

And then, they pulled out a postcard with a photo of the unconformity from this very beach. Suddenly it was just a matter of search and find. With renewed vigor, we clambered about the rocks some more.

John won the search. The four of us regarded it and I resisted the temptation to shrug. We went on a discovery mission as novices, with conflicting information, and found our prize.

The fact that I was underwhelmed by what I saw was a function of my ignorance. Imagine how much Hutton had studied and imagined and studied and hypothesized and studied and theorized in order to spy this and understand its significance. I can see dark colored rocks jutting from the ground at one angle; and on top of them a large rock, flatter and lighter in color, at a different angle.

(I don’t know enough to call the dark ones basal metamorphic rocks, much less Dalradian schists of Precambrian age. Or to recognize the top one an unconformably overlying sedimentary rock of the Lower Carboniferous. But I can look it up on the Internet.)

There’s something more though. Even though we were redeemed, I acknowledge the peculiar power of inhabiting uncertainty. John and I did not know if we’d find the unconformity, and we decided to be happy with the search nonetheless. We went in with clues, observed carefully, and sometimes asserted with shaky confidence that we knew what we were seeing. Through wandering and wondering, I’ve acquired a little bit of new knowledge and new curiosity.

And a couple of new toeholds.

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From Jill:  I’m a health columnist at the Washington Post and an associate editor at HealthNewsReview.org. My husband and I live in Albany; we usually head north to hike in the Adirondack mountains. I’ve heard tell that the rocks there date back a billion years, but I’ve yet to investigate any further. My twitter handle is @juadams. 

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Photos, in order: rock cairn on Arran beach; Tertiary igneous dyke!; Tertiary igneous dyke closeup; and finally, Hutton’s Unconformity.  All taken by author.