Devilish Geology at the Devil’s Marbleyard

The Route to the Devil's Marbleyard

The Route to the Devil’s Marbleyard

Geology was my first love. As a young girl, I discovered a treasure trove of seashells on top of a mountain and ever since, I’ve been  in love with the rise and fall of the lay of the land. Now 30 years old (almost 31!), with a degree in geology and a fair bit of geo-minded traveling under my belt, I can usually stand at an overlook, summon my experiences with orogeny and erosion and tell a fairly accurate story about how the landscape came to be.

From my essay Into the Ojito Wilderness: After wandering around the badlands, we climbed up a steep trail to the top of the mesa and headed northwest, towards a massive eroded anticline with views of Cabezon Peak, a magnificent volcanic neck that I climbed last spring.

Sitting on the edge, my textbook knowledge of anticlines – a convex dome of geologic layers – gradually aligned with the giant scoop-shaped valley in front of me. Here there was once a dome, but over time, the raised center had eroded away, leaving a long, deep, dark red trench capped by a thick angled layer of white crystalline gypsum. A geology lesson, in the flesh!

Self portrait with Dio, the Anticline & Cabezon Peak

Self portrait with Dio, the Anticline & Cabezon Peak

My geology prowess is not invincible, however. Occasionally, I stumble. A few weeks ago, on my first trip to the Devil’s Marbleyard in Virginia, I totally wiped out.

Devil's Marbleyard D.O.G.

Devil’s Marbleyard D.O.G.

Located near the geology-gifted town of Natural Bridge, Virginia, the Devil’s Marbleyard is a jumbled morass of refrigerator, car and bus-sized boulders, strewn over eight acres on the side of a mountain.

When I see fields of boulders, I think glaciers. When ice moves over a landscape, it tears up the underlying rocks and carries them along, often depositing boulders far from their source. I’ve seen a lot of glacial moraines out west and most recently, in Rhode Island. With ice on my mind, the tracks in the rocks, all running parallel, looked like glacial striations: scratches gouged out when two rocks are rubbed together by moving ice.

Parallel lines in sandstone

Parallel lines in sandstone

As it turns out, I was wayyy off. For starters: glaciers never got as far south as Virginia during the last Ice Age. Duh. The Laurentide ice sheet advanced from the Arctic as far south as New York City and Chicago, but no farther. The Appalachian Mountains may have held some ice, but the peaks were roughly the same height 10,000 years ago as they are now, so we’re not talking Rocky Mountain-esque glacier fields (which are fast disappearing).

Nate & Baeya in the Marbleyard

Nate & Baeya in the Marbleyard

So what happened here? As it turns out, the bizarre and beautiful geology of the Devil’s Marbleyard tells a story of ancient beaches, extinct worms, supercontinents and ice crystals. According to the U.S. Geologic Survey, the white rocks of the Marbleyard began as a white sand beach, much like the Outer Banks of North Carolina, around 500 million years ago. The sand was riddled with worms, which left behind copious worm-track tunnels as they moved through the sediment.

Over a period of several hundred million years, the beach was buried and the quartz-rich sediments were compressed and baked into quartzite, one of the hardest metamorphic rocks on the planet. A few of the worm tracks were preserved, all in one parallel plane; tracks in other orientations were obliterated.

Looking back down into the Natural Bridge valley

Looking back down into the Natural Bridge valley, worm tracks on the left. This rock is classified by the USGS as Antietam Quartzite.

Then around 325 million years ago, the continental plate under what is now North America (then known as Euramerica) began colliding with the African plate (known as Gondwana), eventually forming the supercontinent Pangaea and pushing up the Appalachian Mountain chain to Himalayan heights.

For more than 200 million years, the hard quartzite of the Marbleyard lay intact, within the bowels of the mountains, until it was eroded to the surface, largely still in one piece. Then, ice went to work on the rocks, but not in the spectacular glacier-driven methods I imagined. Instead, tiny ice crystals found their way into cracks and fissures in the rocks, perhaps along the ancient worm-trails, and when the ice expanded, it cracked the rocks. Eventually, the entire quartzite ridge tumbled downslope, creating the Devil’s Marbleyard.

The moral of this story: given enough geologic time, worms can bring down mountains!

White Rocks, Blue Sky

White Rocks, Blue Sky

The Devil’s Marbleyard is a great day hike, around 3 miles round trip on the Belfast Trail. You can also connect with the Appalachian Trail from the Marbleyard. Dogs are permitted off leash, but they’ll need to have some serious rock-hopping skills to follow you into the Marbleyard.  The rocks are fairly stable for scrambling, but a few move underfoot and I did hear a couple of minor rockfalls. Click here for directions to the trailhead. 

My dogs deciding for themselves whether they want to follow me into the Marbleyard.

My dogs deciding for themselves whether they want to follow me into the Marbleyard.

Wise Bowie's decision.

Bowie’s wise decision.

Dio being a little bit reckless.

Dio being young and a little bit reckless…

The Devil gets credit for a lot of cool places. Just in the past year, I’ve visited the Devil’s Towerthe Devil’s Postpile, his Punchbowl and now his Marbleyard. Someday, I’ll visit his Causeway

About theblondecoyote

Mary Caperton Morton is a freelance science and travel writer with degrees in biology and geology and a master’s in science writing. A regular contributor to EARTH magazine, where her favorite beat is the Travels in Geology column, she has also written for the anthologies Best Women's Travel Writing 2010 and Best Travel Writing 2011. Mary is currently based in western Colorado. When she’s not at the computer she can usually be found outside -- hiking, skiing, climbing mountains and taking photographs. Visit her website at
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17 Responses to Devilish Geology at the Devil’s Marbleyard

  1. Pingback: Home Sweet Homewood « Travels with the Blonde Coyote

  2. richard says:

    thank you for the great geology lesson.

  3. Chris Major says:

    Great reading, thanks!
    Mighty worms!

  4. Did you ever think of organising the Geology tours?

  5. Fantastic read…my son is jealous!

  6. I especially like the photo “Bowie’s Wise Decision” – it is easy to tell that he’d really like to be out there with you, but knows it isn’t a good idea.

  7. beeseeker says:

    Remember being at the DEvil’s Postpile – just checking out the link now:
    but why does the Devil get all the good place names 🙂

  8. beeseeker says:

    “Worms can bring down mountains”

  9. ritaroberts says:

    Loved this post and the geology lesson Mary Those massive boulders look about the same as they are here in Crete on the high mountains.I know rabbits move archaeology evidence but didn’t realise worms could be as distructive where there’s rock. Brilliant post thankyou.

  10. Pingback: Appalachian Trail: the Devil’s Marbleyard to the James River « Travels with the Blonde Coyote

  11. Shel says:

    Just hiked the Devil’s Marbleyard today. It was thrilling to read about the origin of the “marbles.” Never would have imagined wormholes. Will have to visit again, with a different perspective and look for the ancient trails. Thank you!!

  12. Art scott says:

    Been there several times with the boy scouts. Came up the back side of the mountain. From the road, you don’t think the boulders are that big.

  13. Pingback: Devil’s Marbleyard 8/28/16 – {slightly feral}

  14. Roger Young says:

    Hiked there about three weeks ago and well worth the time. Wondering about the geology of the marbleyard I came across this website. Very interesting about the worms. Thanks for the post.

  15. Robert says:

    Thanks for the Geology lesson! I went 2 days ago for the first time ever and climbed it! I had a ball! I came down and ate, looked up at it and said, “This is too fun NOT to climb again”! So I climbed it a 2nd time! My thighs are hating on me today, but it was worth it! I wondered about the Geology

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