In the desert of northwestern Saudi Arabia, a sandstone boulder about the size of a small house stands split into two halves by a gap so straight it looks machine-cut. It is called Al Naslaa, and it sits roughly 50 kilometers (about 30 miles) south of the oasis town of Tayma. Nobody has pinned down exactly how the split formed, but the leading explanations are all ordinary geology. No lasers required.
The rock also carries ancient carvings of horses, ibex, and people, which makes it interesting to archaeologists as well as geologists. Here is what is known about it, what is still guesswork, and why the “laser” story keeps going around.
What you are looking at
Al Naslaa is one large block of sandstone that has come apart into two pieces of nearly equal size. Live Science and Wikipedia both put it at roughly 6 meters (20 feet) tall and 9 meters (30 feet) wide. The gap between the halves runs from top to bottom and is narrow, straight, and unusually smooth on both faces. Live Science describes it as “pencil-thin.”
The second odd detail is underneath. Each half rests on its own narrow pedestal, so the whole formation looks like it is balancing on two stubby feet. From a distance it can look as if the rock is hovering just above the sand.
The word to know here is sandstone. It is a sedimentary rock, meaning it formed from layers of sand that were buried, pressed, and cemented together over very long stretches of time. Those layers give sandstone built-in lines of weakness, and they also wear away at different rates. Both facts matter for explaining Al Naslaa.
Why the crack is so straight
Scientists have not studied Al Naslaa enough to settle the question, and the popular science write-ups are careful to say so. Still, the main candidate explanations are well understood from other rocks around the world.
A joint. In geology, a joint is a crack where rock breaks apart without the two sides sliding past each other. Joints form when the crust is stretched or squeezed by tectonic forces, or when rock cools and contracts, and they often run in remarkably straight, flat planes. If Al Naslaa had a joint running through it, the boulder would naturally separate along that line. The Wikipedia entry for the rock simply says it is split in two by a joint.
Movement in the crust. Live Science, citing the website Geology Science, notes that this part of Saudi Arabia occasionally experiences tectonic shifts, and one theory holds that a sudden movement fractured the block. In a 2022 Big Think piece, astrophysicist and science writer Ethan Siegel pointed out that features on the back of the rock do not line up perfectly from one half to the other, which hints that some faulting (a break where the sides do shift) may have played a part. He also noted a second crack on one side running parallel to the main gap, a possible clue that the rock has a set of parallel weaknesses.
Freezing water. A third idea is that water seeped into small cracks during a cooler period, froze, and expanded. Repeated many times, that can widen hairline fractures until they join into one clean break. This is called freeze-thaw weathering, and it splits rocks in cold climates today.
Whatever made the first break, something likely smoothed it afterward. A fresh fracture is usually rough. Researchers quoted by Live Science suggest that once the gap opened, it became a channel for wind carrying sand, which acted like slow sandpaper on both inside faces for thousands of years. Rain and runoff may have helped too. Al Arabiya English, reporting on the rock in 2020, likewise said windblown sand and periodic rain could have created the shape, while noting the exact cause has yet to be determined.
Big Think also pointed to the many small horizontal cracks across both halves. They do not match up across the gap, which suggests they formed after the boulder had already split, as each half weathered on its own.
Why it stands on pedestals
The narrow bases are the easier part to explain. Rocks shaped like this are common in deserts, where they are often called pedestal rocks or mushroom rocks. Windblown sand does most of its cutting close to the ground, and lower layers of sedimentary rock are often softer than the layers above them. Over time the base wears away faster than the top, leaving a heavy cap on a skinny stem.
Utah’s Balanced Rock and the chalk formations of Egypt’s White Desert are well-known examples of the same basic process. They also show how it ends. Erosion keeps going, and eventually the pedestal gets too thin to hold the weight. Al Naslaa will fall someday too, though no one can say when.
The carvings on the rock
Al Naslaa is also an archaeological site. Its surface carries petroglyphs, which are images pecked or carved into rock. Researchers have documented carvings of horses, ibex, and human figures, and Wikipedia notes that the rock’s south-east face is covered with them. HowStuffWorks highlights one image of a person leading a horse.
How old are they? The honest answer is that nobody knows precisely. Live Science says the engravings are thousands of years old but that exactly when they were made remains a mystery. The surrounding area has a long human history. Tayma is one of the old oasis towns of the Arabian Peninsula, with archaeological remains stretching back thousands of years.
Where the “laser” story comes from
Al Naslaa has gone viral on social media again and again, usually with a caption claiming it is a 4,000-year-old rock cut in half with laser-like precision. Al Arabiya English quoted one widely shared Instagram post that said nobody knows how it happened and hinted at a lost advanced civilization.
There are two problems with that framing. First, the “4,000 years” figure does not describe the rock itself. Sandstone forms from sediment over geological time, which is measured in millions of years, not thousands. At most, a few-thousand-year figure might fit the human story around the rock, such as the carvings. Second, there is no evidence of tool marks or cutting. The straight line is exactly what a joint or fracture plane tends to produce, and the smoothness is what you would expect after a long stretch of sand blasting through a narrow gap.
It is not the only rock like this, either. New Zealand’s Split Apple Rock, a granite boulder off the coast of the South Island, is split cleanly in two along a natural joint, as Big Think also noted. Al Naslaa is a rare and photogenic example of a common process, not an exception to geology.
The bottom line
Al Naslaa looks impossible at first glance, which is exactly why it gets shared so often. Look closer and the pieces fit known patterns. Sandstone with a built-in plane of weakness broke along that plane, wind and sand polished the inside faces, and the softer base wore down into two pedestals. The precise sequence and timing are still open questions. The rock is worth admiring as one of the clearest natural demonstrations of how patient erosion can be.
Sources: Live Science, Big Think, Al Arabiya English, HowStuffWorks, and Wikipedia.