TOP 10 LARGEST Rock Slabs

Rock. It doesn't break into flat sheets, it breaks away into rubble, which is why a perfectly flat base of stone is one of the strangest things a landscape can produce. But it is possible. So in this video, I'm going to count down the top 10 largest rock slabs. So let's start with number 10, Trolltunga, the only one that you can stand on. 700 meters above a Norwegian lake, a flat tongue of rock is sticking straight out into the air with nothing underneath it. It is the single most slab-shaped object in this entire countdown. It's called Trolltunga, and that's why we're putting it first. Because it's not a cliff face, it's just an actual slab, a discrete flat plane of stone with air above it and air below. The way it got there is pretty cool, and it's the mechanism behind every other entry in this video. Rock contains planes of weakness. In hard rock like granite, those planes are joints, which are fractures that form when the stone that's solidified under pressure deep underground is slowly unloaded. And as the material above it erodes away, relieved of that weight, the rock expands very slightly, and it cracks. It also cracks in sets of roughly parallel families of fractures, frequently meeting each other at close to right angles. And then the water gets into them. The water freezes, expands by about 9%, and levers the crack a fraction wider. It thaws and refills and freezes again. You do that a few hundred thousand times, a hairline joint becomes a crack, and a crack becomes a gap. But this is the interesting part. The rock doesn't crumble. It parts along that plane that was already inside it, and whatever comes away goes away as a single piece. What it leaves behind is the face of that plane, and that's the face that's flat because the weakness was flat. A glacier did the heavy lifting here. During the last ice age, this valley was filled with ice, and when ice retreats, it takes away the support it was providing to the valley walls, which is the moment a great deal of detaching happens. Trolltunga is what was left when the rock around a horizontal joint went away and the plate sitting on top of it didn't. When you arrive here, there is no railing, no barrier, no fence. There's just a flat rock, a line of people waiting to be photographed at the end of it, and 700 meters of nothing. A projecting slab of rock is like a cantilever, which is a beam supported at only one end. A cantilever has a specific weak point, so when you load the free end of a beam that's fixed at the other, the underside goes into compression and the top goes into tension. That's pretty much the wrong way around for a stone. Rock is superb in compression, which is why you can stack it into cathedrals and aqueducts, and it will stand for 2,000 years. But in tension, it's feeble, an order of magnitude weaker and full of the joints and flaws we've just been talking about. Which is why there are very few of these anywhere, and why the ones that exist are geologically young, and why none of them are permanent. Trolltunga is not a stable landform, it's the surviving end of a slab that's being leveled off, that was caught partway through the process. Which does kind of make it the odd one out in this video. Every other entry here is like a face, a plane that you stand back and look at from the bottom or the side. Trolltunga is the only one that you can stand on top of. So it's the only one where you're not looking at the scar, you're standing on the piece that stayed. Number 9. Carrara. 650 quarries, and the slabs are the product. Above the Tuscan town of Carrara there are these mountains with their sides cut off square. These are quarries run through the Apuan Alps above the city in the province of Massa and Carrara. The scale of it is difficult to understand from pictures. There are at least 650 quarry sites in this area and roughly half of them now are abandoned or worked out. And together, the Carrara quarries have produced more marble than anywhere else on the planet. Modern extraction is done here with a diamond wire. This is a continuous loop of cable that's studded with industrial diamond beads, threaded through the rock and run around a pulley system so it saws its way through solid marble, leaving a cut face that you could lay a spirit level against. The quarrymen will pick a line on the mountain, and the mountain is really divided along it, which means Carrara is the only place in this countdown where the flat surface is deliberate rather than inherited. Although, the choose word in that sentence was doing a lot of work, because the choosing is the skill. Marble is metamorphosed limestone. It carries the history of what happened to it, with veins, color changes, and most importantly, hidden fractures. A block can look perfect on all six sawn faces and contain a flaw running right through the middle of it, and that block is worth nothing to a sculptor, because the first serious hit will open it along the flaw, rather than where the chisel went. So the quarryman's real job isn't cutting. It's reading the face before cutting, deciding where the good stone is and where the saw should go. And that judgment is the difference between a block worth of a fortune and several tons of aggregate. This is pretty much why Michelangelo didn't order the marble from a catalog. He came to the mountains and selected the blocks himself at the quarry, which is a really cool detail. It tells you how much of the sculpture is decided before anybody even picks up a tool. Well, this has been going on for a very long time. Even the Romans worked this marble. They called it Luna marble, and it is standing in the Pantheon, in Trajan's column and in the column of Marcus Aurelius. In the medieval period, the Malaspina Marquis owned most of the quarries here, and they rented them to Carrara families who handled extraction and transport. Through the 15th to 17th century, Cybo and Malaspina families oversaw the industry. And in 1564, they created the Office of Marble, specifically to regulate who could take what. The prized grade is called statuario, pure, uniform, white marble. Michelangelo's David came out of these mountains between 1501 and 1504. So did the Marble Arch and the Victoria Memorial in London. By the late 19th century, Carrara Marble had become a significant center of anarchism, and the people carrying it were the quarrymen. They were the main actors of the revolt of January of 1894. Now, it's less surprising than it sounds once you think about the work here. Quarrying is skilled, physically punishing and extremely dangerous. Historically, that combination has produced some of the most radical labor politics anywhere. Well, that danger wasn't theoretical. In 1911, a cliff face collapsed at the Metoli quarry and killed 10 workers who were just sitting down to their lunch. As recently as a 2014 video, men were filmed working these faces with missing fingers and no protective equipment. Everywhere else in this countdown, the flat face is what got left behind. At Carrara, the flat face is the path that the saw took, and the material that was removed. It is in a mosque Mosque in Abu Dhabi is in the Pantheon, and it's standing in a gallery in Florence. 8. The Welsh Slate Quarries The one rock that's natively a slab. In northwest Wales, there are these mountains that have been disassembled into terraces. The reason the industry exists at all here is that the rock does split into flat sheets by itself. Penrhyn Quarry sits near Bethesda. Its main pit is nearly a mile long, about one and a half kilometers. It's about 1,200 feet deep. At the end of the 19th century, it was the largest slate quarry in the world. It has since been overtaken by operations in China, Spain, and the U.S., but it does remain the largest in Britain. Slate starts as mudstone or shale, fine-grained sediment full of platy clay minerals lying in every direction. If you bury it and squeeze it hard enough, in the kind of pressure that builds mountain ranges, those platy grains will rotate. They all swing round until they lie perpendicular to the direction of the squeeze, and once every mineral grain in the rock is aligned in the same way, the rock has acquired a continuous plane of weakness running all the way through. That property is called cleavage, and it's why a slate worker can split a block into a thin, flat, remarkably strong sheet with a chisel and a practiced tap. At Carrara, they saw the marble into slabs because marble has no opinion about where it should break. In Wales, they're not cutting sheets at all, really. They're just persuading the rock to come apart along a plane. That's pretty much why the quarries look the way they do. The galleries and terraces step down the hillside in these flat tiers because the extraction follows the cleavage, so the whole landscape ends up composed of plains. Throughout the 19th century, the industrial towns of Britain were growing faster than anywhere had ever grown, and every one of those terraced streets needed a roof covering that was waterproof, cheap, light enough not to need heavy timbers under it, and durable enough to be left alone for a century. Well, slate is all four of those things, and nothing else available at the time was. So, North Wales became the roof supplier of the industrial world, and the slate went out through purpose-built ports and railways to Britain's cities and then on to Europe, the The Americas and even Australia. At its height, nearly 3,000 quarrymen worked there, but the figure today is closer to 200. The human history of that place is dominated by one event. The Great Strike of Penrhyn began on the 22nd of November 1900 and it ran for three years. Makes it the longest industrial dispute in British history. It split the community completely between men who stayed out and the men who went back through the picket line. The way that division was marked has stayed with the place. Families put a sign up in their front windows reading, there is no traitor in this house. While an earlier strike in 1896 had already lasted 11 months, and the outcome of all of it wasn't a win for either side, the disputes damaged customers' confidence in the Welsh slate as a reliable supply, and orders went elsewhere. But in July of 2021, the slate landscape of northwest Wales was inscribed as a UNESCO World Heritage Site. Extraction still goes on under Welsh Slate Limited, and it worked out to a part of the quarry that now carries a zipline, the Zip World Velocity 2, running over a flooded section of the pit. So basically, a mountain reduced to a staircase of flat terraces by men who stayed out for three years over the right to keep doing it is now protected by the United Nations with a zip wire strung across it. number seven the Bunda Cliffs the one you measure in kilometers along the southern edge of Australia the continent just sort of stops it's not a beach or a slope or a headland it's like a flat vertical wall of pale limestone standing 60 to 120 meters above the Southern Ocean the Bunda Cliffs extend about 210 kilometers along the Great Australian Bight the longest unbroken stretch within that That runs for roughly 160 kilometers. They are the eastern section of something larger still, the Great Southern Scarp, which contains about 820 kilometers. The name is Aboriginal. South Australia formally gazetted Bunda Cliffs in 2014 for the cliff line running from the Western Australian border to the Head of Bight, and the name is recorded as having been given to them by the Aboriginal people, who knew this coast for a very long time before really anybody drew a scarp on a map. Every other natural entry in this video is just hard rock that was split along fractures. This is not. The Bunda Cliffs are Cenozoic fossiliferous limestone, part of the Eucla Basin formation. It was sediment laid down on a seabed, layer upon layer, over millions of years, full of the shells of the animals that made it. Which means the planes inside the rock aren't really cracks, they're just bedding planes, the original horizontal surface between one One layer of sediment in the next. The southern ocean here is about as energetic as water can get, with swells arriving that have crossed thousands of kilometers of open water with nothing to slow them down, and that water undercuts the base of the cliff, cutting a notch into it. When that notch gets deep enough, the rock above doesn't slump or crumble, it just parts along a bedding plane and then drops away as a block. Then the sea removes the debris and starts the notch again. So, this really isn't an ancient feature that's been preserved, it's like a moving front, the live, working edge of a continent, and the flatness is the signature of the mechanism rather than a relic of it. Behind the wall is the Nullarbor Plain, which is where the other half of the story is. The name is from Latin, Nullus Arbor, no tree, and it's as literal as a place name gets, an arid limestone plain effectively treeless. The cliffs here are just simply the edge of the slab where the sea is cut into it. It's really the only slab in this video that you measure in kilometers rather than meters, and it's the only one where a flat face is not the side of a mountain. It is the side of a continent. Number 6. Pedra da Gávea. The inscription and the face are both weathering. 844 meters above Rio de Janeiro, there's a flat-topped rock with a human face on the side of it. And according to a story that's run well for over a century, an ancient inscription carved across one of its walls. Both of them, though, are erosion. Pedra da Gávea is a monolith of granite and gneiss standing in a forest. It's a granite dome with a flat top capped by a layer of granite roughly 150 meters thick, sitting on gneiss underneath. The granite dates to around 450 million years old, and the gneiss to about 600 million. It's described as one of the highest mountains in the world that ends directly in the ocean, and that's really why it's on this countdown. This is a vertical rock wall several hundred meters just dropping into the Atlantic with the city of six million people living around its foot. The name of it, though, came from sailors. Captain Gaspar de Lemos' expedition, he left Portugal in 1501 and sighted this mountain on the 1st of January, 1502. And what they saw in its silhouette was the topsail of a carrack, a gávea, the rock of the topsail. Well, it was the same voyage that looked to the mouth of the Guanabara Bay, decided it was a river, and then left the city with the name Rio de Janeiro. The inscription is the bigger of the two claims here. Markings on one face were argued to be Phoenician writing, which, if true, would put Phoenician sailors in Brazil and rewrite the history of the Atlantic Ocean. It's a wonderful idea, and it's really never gone away. But it is also settled. In the mid-1950s, Brazil's own Ministry of Education and Health published the geologist's conclusion. The markings are weathering that happens to resemble writing. Well, the face is the other one, and it is striking. From the right angle on one side of the mountain, it carries what reads unmistakably as a stylized human head. Forehead, brow, nose, chin, the whole lot. Now, that is differential weathering. The rock here is not uniform. Some parts of it are more resistant than others, so weathering removes material unevenly. Occasionally, the surviving shapes land in an arrangement that our visual system reads as a Because our visual system is extremely eager to find faces. Geologists file it under pareidolia. The Brazilian archaeologists don't treat the mountain as an archaeological site at all. Everything in this countdown is like a flat plain created by the rock along a weakness. But to a human being, a flat plain is the signature of being manufactured. We make flat things. Nature mostly doesn't. So our brain has learned to treat flatness, straightness, and regularity as evidence that somebody was there. Which is a very useful instinct almost everywhere. Except standing in front of a cliff. The mountain was named in 1502 by men who looked at it and saw a sail, and five centuries later, people look at it and see a carved inscription and a portrait. Nobody in all that time has had much success looking at it and just seeing a rock. 5. Half Dome The missing half is still there. Half Dome is 2,696 meters above sea level in Yosemite, and it's made of quartz monzonite. It's an igneous rock that solidified a long way below the surface, dated to the Cretaceous period, about 93 million years ago. What you're looking at is the inside of a magma chamber that cooled underground, and was later exposed and cut in by erosion. The name of it does an enormous amount of damage because it arrives with a complete explanation attached to it. This was once a whole dome, and a glacier came down Yosemite Valley, sheared off the northwestern half, and carried it away. Well, essentially none of that is right. The geological assessment is blunt about it. The appearance of a round dome that's lost its northwest half is an illusion, and roughly 80% that's supposedly missing is just still standing Four-fifths of it never went anywhere, so if nothing was sliced off of it, why is the face flat? Well, joints, as is everywhere else in this video. Where those joints are closely spaced, the rock is divided into manageable pieces and it comes away readily, so up the side of the mountain will develop a cliff aligned with the joint plane. Where the joints are widely spaced, the rock is massive and essentially unbroken, so it weathers instead of exfoliation, that's the onion skin peeling of curved sheets, and that process rounds a rock mass off into a dome, which does mean the same granite in the same mountain in the same weather can produce a sheer vertical face on one side and a smooth rounded dome on the other, for one reason, the spacing of the cracks inside it. Nothing was taken from one side, one side simply had planes in it and the other didn't. Glaciers, though, did play a small part, but a much smaller and more specific one than the story claims. Ice moving through Tenaya Canyon steepened and cleaned out the flank, removing material and leaving the wall standing. But the glaciers never reached the summit of Half Dome, and no glacier cut a dome in half. The ice carried the rock away that the joints had already prepared for carrying away. Josiah Whitney, the state geologist of California and the man the highest mountain in the lower 48 is named after, inspected Half Dome and pronounced it perfectly inaccessible. Well, in October of 1875, George Anderson got to the top. His method, faced with bare curving sheet of granite offering nothing to hold on to, was drilled with iron eye bolts into the rock and he hauled himself up one at a time. Confronted with a surface that had no features, he just installed some. So, the northwest face is not a scar of an ancient amputation, it is an active surface still coming off in slabs, and it's still getting marginally flatter and marginally bigger. Which means the missing half is, in fact, still going, just not in the way or at the speed or for the reason that the name implies. Number 4. The Troll Wall The top overhangs the bottom by 50 meters, In Romsdalen Valley in Norway, there's 1,100 meters of rock standing more or less straight up. And at its steepest, the top of it leans out past the bottom by nearly 50 meters. The Trollwall is the tallest vertical rock face in Europe, rises about 1,100 meters from base to summit, with its highest point, Stortroltind, standing about 1,700 meters above sea level. Now, the overhang figure is the one to talk about for a second because it's really difficult to picture properly. If you drop a plumb line from the steepest part of the summit ridge and it doesn't touch the wall on the way down, it lands roughly 50 meters out from the foot of it. Now, there's a volume of empty air between the rock and the vertical that would comfortably contain an office block. The rock is what's known as nice, cut by large corners, concave roofs, and crack systems, and the thing every account of this wall agrees on is that it's loose. Rockfall here is not an accident, it's the normal condition of this north-facing face in this state. In September of 1998, a series of large rockfalls significantly changed several of the climbing routes. Now, routes on this wall had been established, named, graded, and then written into guidebooks, and they just stopped existing because the rock they consisted of just left. Which is really the point about slabs that's easy to miss when you're looking at a picture. A face like this isn't a landform in the sense that a mountain is. It's a process that you just happen to catch in the middle, and the flatness isn't the finished state. It just happens to be the current state. The first ascent of it in 1965 came down to a race that almost nobody outside Norway knows about. A Norwegian team of Ole Einarson, Leif Patterson, Odd Eliassen, and Jon Tigeland got up first, finishing one day ahead of a British party of Tony Howard, Jonny Mat, and Bill Tweedale, who were on the wall at the same time and whose line became the Rimen Route, the popular way up. Two expeditions independently on the biggest wall in Europe, separated by about 24 hours. But then there's the parachuting, because that overhang makes this one of the defining sights in the history of the sport. 50 meters of overhang means somebody stepping off the face has clean air beneath them from the first instant, with no wall to be blown back against. Which is precisely what a jumper wants, and precisely what almost no cliff provides. The Finnish jumper Jorma Oster made the first parachute jump from the wall in 1980, and it became a destination after that. Eight base jumpers are known to have died at the Troll Wall, though, the most recent of them in 2012. Jumpers reportedly still use it most summers and reportedly still tend to be gone before the police arrive. Which basically leaves the Troll Wall as a great illustration in this video of a thing that's very hard to accept while standing at the bottom of it. That wall is not solid, it's not finished yet, and it is not safe. It's a kilometer of rock in the middle of coming apart, and the reason it looks so impressive... is that it's doing so neatly. Number three El Capitan The reason it's so smooth is that it throws pieces off. At the western end of the Yosemite Valley, there's a single piece of granite that rises more than 3,000 feet out of the ground. It's the rock face everybody pictures when they hear the word. El Capitan formed from magma that cooled somewhere between 120 and 185 million years ago, most Most likely in a subduction setting where one tectonic plate was sinking beneath another. Later brought to the surface by erosion and uplift, glaciers through Yosemite Valley stripped away the rock and around it, they just left the granite standing. It has two main walls, the southwest and the southeast, with the nose running down between them as a projecting prow. And El Capitan is most commonly described as the largest granite monolith in the world. It's a defensible claim, but that's a bit narrower. It is the largest granite monolith in the United States. And it's not really the highest granite feature in its own national park because Half Dome at number 5 is still higher above sea level. So the most famous rock wall on Earth holds a national record rather than a global one. Think back to Half Dome, where the whole explanation came down to joint spacing, closely spaced fractures on one side that produced a cliff, widely spaced fractures on the other producing a dome. El Capitan is what happens when you take the second case to its limit and apply it to a wall. The granite here is exceptionally massive, there are very few through-going fractures in it, which means there's very little to interrupt the surface. And that's pretty much why it matters so much to climbers. Because it's the opposite of intuitive. A heavily jointed cliff is frightening, but it's full of features. Cracks to put protection into, ledges to stand on, and places to stop and sleep. A massive unjointed cliff offers almost none of that. El Capitan is not hard because it's steep, but because it's blank. The documented hazards on El Capitan include fatal falls and rock falls called by flakes of rock that peel away from the surface. That's known as exfoliation. Curved sheets of granite will detach parallel to the face. Sometimes they're small, but sometimes they're tons at a time and they drop. Each one takes on an irregularity and leaves the wall marginally flatter and marginally larger than it was. Which means the smoothness isn't a finished quality that the rock happens to have. It's the continuing result of the wall shedding its own surface Its climbing history is now the most watched in the sport, and it began with a siege rather than a sprint. The Nose was first climbed in 1958 by Warren Harding and his partners, and the way they did that tells you what they were up against. The ascent wasn't a continuous push, it was spread across 18 months, in installments, with the team retreating and returning, fixing ropes up the wall as they went, and the final effort alone took 12 days. Total time spent on the rock came to 47 days. Harding's team drilled and hammered their way up, placing hardware into the blank granite to create holds and anchors in the rock that refused to provide any, which is the same answer that George Anderson arrived at on Half Dome 80 years earlier, with eye bolts. The nose is the great line. Alex Honnold climbed a freerider route in 2017 with no rope and no equipment to catch him, which remains the most widely known single act in the sport's history. Sela Schneider became the youngest person to have known to climb it in 2019. And in 2024, Babzy Zengirl flashed Freerider, which deserves a bit of translating because to a non-climber it just sounds less impressive than it actually is. A flash means climbing the route cleanly on the first attempt, with no prior practice of it. On 900 meters of granite at that difficulty, it had been regarded as essentially out of reach. So the wall is famous for being blank, but now has been climbed without a rope and climbed, first try, within seven years. But it's still peeling, continuously, which is the only reason it was ever blank enough to be worth the climb at all. 2. The Great Trango The first man up the East Face died on the way down. In the Karakoram, above a glacier in northern Pakistan, there's a wall 1,340 meters high that holds the record for the greatest nearly vertical drop on Earth. Now note that word, nearly, it's doing a great deal of work there. The Greater Trango Tower stands 6,286 meters and is the highest point of its group, with three summits, the main, the east at 6,231 meters, and the west at 6,223. Besides it is the Nameless Tower, sometimes just called Trango Tower, at 6,239 meters. The rock here is granite, and the east face of Great Trango, specifically its east-southeast headwall, measured at 1340 meters. That's the wall in question. Let's put some scale for that figure. It's more than four times the height of the Eiffel Tower, standing as one continuous face. It's about a third taller again than the Troll Wall at number four, which is the tallest thing of its kind in Europe. And unlike the Troll Wall, which has a main road running along its valley, the foot of this one sits on a glacier at 4,000 meters, which means the largest near-vertical rock face on the planet is seen in person by only a handful of people each year. Its climbing history is one of the greatest sequences in mountaineering, and it starts beside the main event. In 1976, the Nameless Tower was first climbed by a British party of Joe Brown, Mo Antonin, Martin Boyson, and Malcolm Howells. The following year, Great Trango itself was climbed for the first time by the South Face by Galen Rowell, John Roskelly, Kim Schmitz, Jim Morrissey, and Dennis Hennick. But the East Face was the prize, because it was the biggest of all. In 1984, two Norwegians, Hans Christian Døseth and Finn Dale, made the first ascent of the East Face to the East Summit. They both died on the ascent. It took eight more years before anybody climbed it and came home. In 1992, Xavier Bongard and John Middendorf completed the first successful ascent of, and returned from, the East Summit by a route they called the Grand Voyage. It took them 18 days. The same year, Nick Federus and Glenn Singleman climbed Great Trango, then jumped off of it, base jumping from 5,955 meters, which remains the highest recorded base jump start. The rest of the record keeps going. Catherine Destivelle made the first ascent by a woman in 1990, free climbing it. Eternal Flame on the Nameless Tower was climbed almost entirely free in 1989, and then fully free by Huber Brothers in 2009. Alex Lowe, Jared Ogden, Mark Sinek put up parallel worlds on the West Summit in 1999. And in 2024, Chantal Astorga, Christina Lustenberger, and Jim Morrison made the first ski descent of Great Tango by the West Face. There is also one more name attached to the East Face. Rolf Bagnold repeated the Norwegian route on it and died in the summer of 2008, one of the 11 climbers killed on K2 that August, about 30 kilometers away as the crow flies. Number one, Mount Thor. It leans out over your head by 15 degrees. In the Canadian Arctic on Baffin Island, there's this cliff that hangs out over its own base for 1,200 meters and nothing on Earth is steeper than that. Mount Thor rises to 1,675 meters. Its drop is 1,200 meters, about 4,100 feet, which is the greatest vertical drop anywhere in the world. The cliff overhangs at an average angle of 105 degrees, 15 degrees past vertical for the entire height of it. It's in a national park on Baffin Island in Nunavut. The rock is solid granite, pre-Cambrian, with the dates on it running somewhere between 570 million and 3.5 billion years old. First though, let's settle the question left hanging at number two because these two cliffs are confused constantly. Great Trango's east face is bigger, 1340 meters against Thor's 1200, but Trango holds the record for the greatest nearly vertical drop. Thor holds the record for the greatest vertical drop. Those are two separate records, and the reason they're separate is that Thor's face isn't vertical. The whole thing is overhanging. You stand on the summit, you lean out and drop a stone, it won't touch the rock on the way down. It'll just fall 1200 meters down. In every case so far, we've had a flat plane that was created by rock parting along an internal fracture, a joint in granite, a bedding plane in limestone, even a cleavage plane in slate. The detaching mass slid or toppled outward and downward off the front face, and what was left behind stood vertical or leaned back. You can't really produce an overhang that way. Material doesn't slide off the underside of a leaning wall. For a face to overhang, the rock that used to be there had to leave while carrying the weight of everything above it, which means the joint plane it parted along was dipping back into the mountain, rather than out of it. When the slab went, it went outward and intact, with a kilometer of granite left sitting over the gap it vacated. That's why 105 degrees is close to the ceiling. You lean a rock wall further out than that, and the stone above the overhang has to hold its own weight across a gap in tension. We talked about that problem at number 10, standing on Trolltunga. You push past the angle a certain point, the roof cannot hold itself. It'll fall. Overhang collapses, and what you're left with is an ordinary vertical cliff. So Mount Thor isn't just the steepest cliff in the world, it's approximately as steep as a cliff is allowed to be. The most extreme slab on the planet is sitting more or less exactly on the physical limit for slabs. And then there's who climbed it first, which is a great footnote in this video. The first ascent was made in 1965 by Donald Martin and Lyman Spitzer on an Alpine Club of Canada expedition led by Pat Baird. Lyman Spitzer was an astrophysicist at Princeton. In 1946, before NASA existed, before anything had been put into orbit, he wrote the paper laying out the case for operating a telescope above the Earth's atmosphere, and then spent decades arguing for it until it happened. The Hubble Space Telescope is substantially his idea, and the Spitzer Space Telescope carries his name. Donald Morton was an astronomer too. So basically, the first two people to stand on top of the most overhanging cliff on Earth were astronomers, and one of them is the reason we have space telescopes. The wall did keep its reputation afterwards. The West Face was first climbed in 1985 by Earl Redfern, John Bagley, Eric Brand, and Tom Bepler. Yasushi Yamanoi soloed the West Face in 1988. Jason Smith soloed it again in 1998. Bill Borger, John Furneaux, they made the first free climb of the Southwest Buttress in 2012. And the name of this park around it is the right note to end on. Uyutuk. It means roughly the land that never melts. So if we run back through all of it, Trolltunga is a cantilever of stone loaded in the one direction rock is worst at resisting. Carrara has at least 650 quarries where the flat faces are the path the saw took and the material removed is standing in the Pantheon. Penrhyn's Great Strike ran for three years, the longest industrial dispute in British history, over a rock that was only ever valuable because it had a plane built into it already. The Bunda Cliffs hold a flat vertical front across 160 unbroken kilometers. Pedra da Gávea's famous inscription and its famous face are just both weathering. Half Dome still has something like 80% of its missing half, and the only difference is between the wall and the dome is how closely the cracks are spaced. The Troll Wall shed enough rock in September 1998 to delete established climbing routes from the guidebooks. El Capitan is blank because it's continuously peeling itself flat, and Great Trango has the greatest nearly vertical drop on Earth, first climbed by two men who didn't survive the ascent. Every single one of them is pretty much the same object underneath. Not a lump of rock, it's a plane. And a plane is not something that was built or carved or gradually worn smooth. It's the surface which a rock was already divided. Which means that none of these are really a monument, they're all absences. We just simply got to the habit of photographing the wall that stayed behind, and calling that the feature. And on Baffin Island, the absence leans out over your head by 15 degrees, because the piece that left took a kilometer of granite's worth of support away with it, and what remains is holding on in tension. Which is the one thing that Stone was never any good at.