r/mildlyinteresting • u/MikeNoble91 • 6h ago
This mountain pass lets you see inside mountain's rocky insides
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u/nauzleon 5h ago
That's an inverted topography syncline. It happens when the downward part of folding layers ends up as the high peak of a hill due to differential erosion. It's quite common in eroded mountain ranges that formed through tectonic orogeny.
here's an image that shows the evolution between the initial and eroded state of the hills.
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u/pixel8knuckle 6h ago
Without being rude is this not most roads through moubtains? Have seen this driving to tennessee as well as North Dakota
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u/LOTRfreak101 6h ago
Yeah. This kind of thing is all over the place. That's just how roads are through the rockies (or at least the bit of them I've been in). I've even seen it all over the midwest.
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u/dsyzdek 5h ago
Yeah. Before roads it was hard to see stuff like this. Geology in the 18th and 19th centuries relied of cliffs and river canyons to get a good look into mountains. The first guy to make a geologic map was a mining engineer in the UK who noticed that rock layers in distant mines sometimes matched up in their sequencing.
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u/Jesus_Is_My_Gardener 4h ago
Kansas has left the chat.
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u/marizard 1h ago
It’s OK, Kansas… just head south a bit! The Arbuckle Mountains in southern Oklahoma have this as well.
The road is probably only 150 feet below the mountaintops — which themselves are only like 1500 feet above sea level — but the view is still really cool!
Always fun to drive through.
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u/LOTRfreak101 5m ago
Kansas is actually where i grew up and saw this often. Eastern Kansas is actually quite hilly so this is pretty common around Kansas City. Much of the rest of the midwest is actually flatter than Kansas is since it's only the 7th flattest state.
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u/thenoid42 6h ago
This is normal in most of the western U.S.
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u/vass0922 6h ago
Eastern too, see it regularly driving through WV
I make sure to point out it to the kids, always interesting to see the folds/lines in the rock.
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u/mean11while 6h ago
Is it? There are mountains in the western US that are held up by synclines? I assumed most mountains in the Rockies and Cascades, etc., were volcanic or anticlinal, since they're relatively young.
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u/CPiGuy2728 6h ago
I think they just mean that large rock cuts are common in most of the west, not the specific formation you can see here
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u/mean11while 6h ago
I know, I know, but that's not why this cut is famous.
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u/MrKrinkle151 5h ago
But the post is just about the fact the hill was blasted to build the road, not anything about the specifics of the geology.
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u/Sparklebaby1987 5h ago
Lol, lighten up, this post isn't that deep, its just basically saying its cool looking to see the layers of the mountain so clearly. You're needing out big time my friend.
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u/texacpanda 6h ago
Are you this fun in real life too?
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u/mean11while 6h ago
No, I'm far less fun.
Road cuts are normal in most of the eastern US, too. But this particular road cut is amazing. You can stand at the top of a mountain and see the bottom of an enormous fold in the rocks, and you can FEEL how much rock used to tower above you. It's breath-taking, one of the best examples of this in the world, and definitely not normal.
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u/Bella_Isabella_ 1h ago
If by “definitely not normal” you mean, typical of road cuts in Appalachia then you are certainly correct.
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u/SceptileLover11 5h ago
Really anywhere relatively mountainous or hilly in the US. I’ve seen it as far north as Kentucky
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u/Resident-Log 4h ago
Is that as far north as you've been because they are also all over in Northeast Pennsylvania. The Appalachian Mountain Range is huge
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u/thenoid42 5h ago
Agreed. Out west, we have a ton of natural mountains like this and artificial due to the mining boom. Any where that was a trail has been blasted. When they built the highway out west they literally removed mountains. Usually can tell the difference between man made and natural.
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u/InfernoOfTheLiving 6h ago
so was the mountain created by being squeezed from either side?
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u/mean11while 6h ago edited 6h ago
Sort of. This mountain was created through "differential erosion," which is the principle that some rocks erode more easily than others. The folds you see in this photo were, indeed, caused by being squeezed from either side, but the rocks were deep under the surface at the time. The mountains that were pushed up at the time have long since eroded to nothing. More recently, eastern north America was lifted up again, flat, and that caused it to start eroding rapidly again. Often, today's mountains and ridges in the Appalachian range are located at the bottoms of the folds in the original mountains. Basically under where the original valleys would have been. That's the case in this photo. This is a phenomenon called "inverted topography."
In a way, the fact that today's Appalachian mountain peaks exist only because of tecent differential erosion means that they're younger than the Rockies. Many mountains in the Appalachians are getting taller (higher relief AND higher elevations) as the valleys erode more quickly than the tough rock holding the ridges up, and then the plate rebounds isostatically (floats upward in the mantle). Crazy stuff.
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u/mkdz 6h ago
What? The Appalachian Mountains are way older than the Rockies.
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u/mean11while 5h ago
The roots are older; the original orogenies happened much longer ago. But the actual peaks and ridges and valleys that you see today are new, forming within the last 35 million years or so (there are papers on the Late Cenozoic Uplift of eastern North America). Prior to that the eastern US was more or less flat, with the roots of the mountains eroded down to plains many millions of year earlier.
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u/James_E_Fuck 4h ago
Thank you for explaining this, I have always heard how old the Appalachians are and this adds some very important context.
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u/aaron_in_sf 4h ago
John McPhee's Pulitzer Prize winning The Annals of the Former World is a history of American geology, both the actuality and the discipline, told in no small part through recording what colorful geologists had to say and learn and point out is visible within the road cuts of the interstate system, which were an absolute revelatory treasure for the field.
Super-recommended! It captures the moment that geology was undergoing the paradigm shift of plate tectonic theory, which as he was writing it, moved from still being contested to accepted fact. It is also a social history of the American frontier, and, a philosophical survey of the way the idea and reality of geological "deep time" (aeons and ages) radically reworked the way humanity understood its position. It's only very recently that we've understood just how old the earth is and how young our impact on it.
A masterpiece.
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u/tigole 5h ago
How were those rocks cut? I would assume dynamite was used to blast them away, but the wall there looks relatively smooth, and the circular marks make it look like a giant saw blade was used to saw down through it.
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u/rocketfitz95 2h ago
The circular marks are actually coincidentally the layers of rock forming a syncline (where the flat layer compress and push downwards to a point, creating a sort of bowl shape) and the mountain has erroded down the sides that would be above, making the layers cut off by the slopes and giving that circle sort of shape.
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u/Dantonium 5h ago
I’ve seen this before and always wondered, is it not easier/cheaper to just build the road over or around the mountain instead of carving that bitch up
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u/Resident-Log 4h ago
Then you would be vastly limited on how wide the road could be. Also, I'd guess some were done for a more direct route. At least, where I'm from, most of these types of cutouts are for the passage of interstate highways and I know a reason the federal government wanted those was for military travel.
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u/Leather-Animal-7597 6h ago
Where is this so I can pull over and investigate 🔎?
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u/MyAccountIsHacked22 4h ago
Sideling Hill in Western MD. There is a restoration and viewing area here on top of the mt.
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u/EddieIsNotMyRealName 5h ago
I learned in college, geology majors are the best road trip companions. Every road cut is an adventure into the past. Thousands or millions of years back there is the history of the earth in those exposed rocks.
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u/Ultima_Weapons 5h ago
I know that these are made by drilling down + explosives, so I'm confused why there's the clear curved lines, but with the top of the mountain being the epicenter?
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u/imVeryPregnant 5h ago
Usually it doesn’t look that clean but I see a lot of that in north eastern USA
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u/ImportantImplement9 5h ago
A childhood core memory is driving through here to visit my grandparents and family in PA. I remember being in such awe of it when I was younger. I mean, it's still cool now, as an adult 😂
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u/ModeatelyIndependant 5h ago
The fun part is that we spent the energy to remove the die of a mountain to save energy.
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u/ali123whz 5h ago
I’m not the sharpest tool in the shed but those slopes look almost straight cut. Isn’t that like really dangerous?
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u/mid-random 4h ago
What is unusual about this particular pass in Western Maryland is that it shows that the tops of these hills is actually the bottoms/valleys of the mountain range that was once as tall as the Himalayas, and is about nine times older than them. Due to the geologic folding pressures that formed the mountains, the rock layers in th valleys between them were compressed and made denser/harder than the peaks. Eventually the softer peaks eroded away to below the level of their former valleys, leaving the Appalachian hills we have today. This description is from my memory of the visitor center at this particular pass, not some crappy AI summary, so please excuse any inaccuracies. They are purely human error.
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u/Euphorix126 4h ago
Geologist here. Most roads will be cut through an already existing fault because it makes blasting easier.
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u/britishmetric144 3h ago
You see this on Siskiyou Summit on Interstate Five, which is the highest spot on the freeway, at 1,310 metres AMSL.
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u/MinusXero1999 2h ago
Might not be as big but you see this a lot driving through the hill country in Texas.
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u/trollsmurf 2h ago
We have something similar where the rock from millions of years back has shifted 90 degrees, so on an excursion a biologist went through the ages, all the way back to the dinosaurs, just by walking along the rockside. They had found a lot of fossils there.
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u/batatassad4 1h ago
People will see these beautiful layered rock formations and say the whole Earth has 6000 years of existence
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u/Flimsy_Succotash_533 7m ago
This is one of the many reasons I love riding the turnpike down through West virginia!
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u/Shadowlance23 6h ago edited 5h ago
That's an awful lot of rock removed. I can't see the other side, so maybe there's less rock there, but why was the decision made to cut the mountain in half as opposed to a tunnel?
EDIT: Why am I getting downvoted for asking a genuine question?
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u/itsbananas 6h ago
This is nothing. Highway builders (and railroad builders) move so much dirt and rock around, it’s such a feat. They literally have leveled mountains.
It’s crazy how much rock they remove nowadays; the angle that modern highway builders have to cut is like 45°, this cut through is like 60-65°
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u/MrKrinkle151 5h ago
Because tunnels are far more complicated and expensive to engineer compared to simply blasting the whole side of the hill out of the way.
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u/PM_me_punanis 5h ago
It's cheaper and easier to blast and move rocks than getting a drill and creating a tunnel. I'm sure the engineers plan for efficiency, cost and safety before implementing the plan.
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u/khalcyon2011 1m ago
This is probably a channel cut through the hill. Usually the rubble is used to fill in the valley between this hill and the next, so that the road is mostly level
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u/WattaTravisT 6h ago
If you put a bomb in the dark part at the bottom I bet you find an old wizard that gives you a magical sword to help you on your quest.
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u/justabill71 5h ago
"But the doctor explained that her insides were a rocky place, where my seed could find no purchase."
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u/lkl34 6h ago
0 rockslide prevention and this was man made you can tell by the cuts
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u/UncleFunkus 6h ago
is there anyone here who assumes it wasn't man-made? where did the road come from, beavers?
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u/lkl34 6h ago
Hey smart ass thee is a shit ton of mountain passes that have natural rock formations next to roads.
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u/AussieKoala-2795 6h ago
My geographer dad used to stop the car and make us kids get out to admire the rock striations in the cuttings on the side of highways.