Geologists Just REVEALED What’s REALLY Hiding Inside Wyoming’s Devils Tower!

In a remote corner of northeastern Wyoming, there is a mountain that looks completely out of place. It rises almost straight out of the surrounding landscape, with enormous stone columns running from its base toward a surprisingly flat summit. From a distance, it resembles a giant tree stump. Up close, the rock looks almost engineered, as if someone had assembled thousands of enormous stone pillars into a single structure. This is Devil's Tower, one of the most unusual geological landmarks in North America. The tower rises about 1,267 feet above the nearby Belle Fourche River Valley. Some of its individual columns are hundreds of feet long and nearly 10 feet wide. Many have five or six sides, forming patterns so regular that visitors often struggle to believe they developed naturally. But what makes Devil's Tower truly unusual isn't just its appearance, it's the fact that geologists have spent more than a century trying to establish exactly how it formed. One explanation suggests it is the remains of a volcano that disappeared millions of years Another proposes that it developed entirely underground, when molten rock forced its way into ancient sedimentary layers. A more recent hypothesis even involves explosive interactions between magma and groundwater, yet they all attempt to explain the same enormous stone monument. What scientists do know is that Devil's Tower was once buried beneath the Earth's surface. The rocks surrounding it gradually disappeared, leaving behind a formation that looks as though it rose out of the ground. And understanding how that happened takes us back roughly 50 million years, to a time when Wyoming looked nothing like it does today. Today, Devil's Tower stands among forested hills, grasslands, and layers of colourful sedimentary rock. These surrounding formations Some were deposited during the Triassic and Jurassic periods, when the region experienced environments ranging from dry coastal plains to shallow seas. At different times, sand, mud and mineral-rich sediments accumulated in thick layers. Over millions of years, these deposits hardened into sandstone, shale and gypsum-bearing formations. You can still see parts of this history in the hills surrounding the monument. The different colours represent rocks formed under different environmental conditions long before the magma responsible for Devil's Tower appeared. During the Laramide Orogeny, a prolonged episode of mountain building that began around 80 million years ago, enormous tectonic forces reshaped western North America. The Rocky Mountains developed through major deformation and uplift while the Black Hills region was also raised and and structurally altered. Deep beneath the surface, conditions allowed magma to move upward through the crust. In the region around Devil's Tower, magma intruded into older sedimentary rocks. The exact path it followed remains uncertain, but at some point, a substantial quantity of molten material collected and eventually solidified. What is extraordinary is that the recognisable tower wasn't standing above the landscape when this happened. According to the National Park Service, the magma originally solidified at a depth estimated at approximately 1-2 miles beneath the surface. The landmark we recognise today would emerge much later after enormous amounts of surrounding material had been removed. Although its dark appearance and towering columns resemble some basalt formations, Devil's Tower isn't made of ordinary basalt. Geologists classify the rock as phonolite porphyry. Phonolite is an uncommon type of igneous rock, Rich in certain feldspar minerals and relatively poor in silica compared with many familiar continental rocks, if you examine a fresh piece of Devil's Tower rock closely you can see larger mineral crystals surrounded by much smaller ones. Some of its feldspar crystals measure around half an inch across. Large crystals can develop while molten material remains hot enough for minerals The finer material surrounding them records additional crystallization as the matter magma cools. The process isn't necessarily as simple as one period of slow cooling followed by one period of rapid cooling. Magma can experience changing temperatures, pressures, and chemical conditions as crystals grow. The tower is not an ancient sedimentary formation, a collection of fossilised trees, or a structure assembled from separate blocks. It is one enormous body of igneous rock divided by natural fractures. But rock composition alone doesn't tell them what the original magma body looked like. The same general type of molten material can cool inside a volcanic conduit, an underground intrusion, or another volcanic structure. Scientists had identified the material, but they still needed to reconstruct the environment in which it solidified. For many years, one explanation seemed particularly convincing. Devil's Tower might be the surviving neck of an ancient volcano. A volcanic neck forms when magma hardens inside the central passage of a volcanic system. Imagine an active volcano with molten rock moving upward through a conduit. Some of that magma reaches the surface, producing lava flows or explosive eruptions, while some remains within the conduit and eventually solidifies. After millions of years, the softer surrounding material may disappear, leaving the hardened rock that once occupied the volcano's interior. Viewed this way, Devil's Tower could represent the remains of a much larger volcanic structure. If a substantial volcano once stood here, scientists might expect to find large Lava flows, volcanic ash, or deposits of fragmented material associated with eruptions. Those deposits have not been clearly identified around Devil's Tower in a way that conclusively establishes a former volcanic cone. It doesn't prove that a volcano never existed. Erosion could have removed volcanic deposits along with the original mountain, but it makes the volcanic neck theory difficult to confirm. A volcanic conduit would have connected the magma to the surface. Evidence of such a connection could potentially help distinguish this explanation from other types of intrusion, so the old volcano theory remains a possible interpretation. But the National Park Service does not describe Devil's Tower as a conclusively identified volcanic neck. Instead, scientists have considered another possibility that doesn't require a surface eruption at all. Instead, it pushed upward through existing sedimentary rocks ...and became trapped underground... As more molten material accumulated, it forced its way into a relatively confined space. Eventually, the magma cooled, crystallized, and became a solid igneous body. This is the basic idea behind the intrusive origin of Devil's Tower. Intrusions can have very different shapes. Some form narrow sheets, others produce extensive underground bodies, and some spread between sedimentary layers. In 1907, geologists Nelson Wilson Horatio Darton and C.C. O'Hara proposed that Devil's Tower might represent the eroded remains of a laccolith. A laccolith develops when magma pushes between existing layers of rock and lifts the layers above it into a dome. If erosion later removes most of that structure, only part of the original igneous body might survive. That could help explain why Devil's Tower appears so isolated today. A different interpretation appeared in 1956, when US geological survey geologist Charles S. Robinson published a detailed geological investigation of the monument. Robinson favoured the idea that Devil's Tower represents a relatively small igneous intrusion, often described as a stock. Under this interpretation, the original body of hardened magma may have been broadly similar in shape to the visible tower. This explanation does not require a large volcanic cone or an enormous mushroom-shaped intrusion. Yet even Robinson's investigation could not determine every detail of the original magma body, and while the origin remained uncertain, the tower's extraordinary columns were providing another source of evidence. It isn't covered in random cracks. Instead, its surface is divided into long, mostly vertical columns, many of which have remarkably straight boundaries. These formations are produced by a geological process called columnar jointing. The process begins when molten rock cools. As its temperature decreases and it solidifies, the rock contracts. That contraction creates internal stress. When the stress becomes great enough, fractures begin developing through the material. Rather than forming completely random networks, these fractures can organize into polygonal patterns. Hexagons are common because networks of fractures meeting at roughly equal angles can distribute contraction across a cooling surface efficiently. Devil's Tower contains five-sided columns and other irregular shapes, and some columns change geometry along their length. That variation is an important part of the geological evidence. The fractures generally develop in directions related to how heat escapes from the cooling rock. Their orientation can therefore preserve clues about the thermal conditions inside the original magma body. Others bend or flare outward, particularly near the lower parts of the formation. These differences may reveal how cooling progressed through the intrusion. Individual columns can approach 10 feet in width, far larger than the narrow columns visible in many other famous examples of columnar jointing. The Giant's Causeway in Northern Ireland and Devil's Postpile in California are well-known examples of similar fracture patterns. Column size depends on several interacting factors, including cooling conditions, fracture development, and the physical properties of the rock. Slower cooling can favour wider spacing between fractures under suitable conditions, although the relationship is not identical in every igneous body. At Devil's Tower, the unusually large columns suggest a substantial mass of hot material that experienced a distinctive cooling history. Can their shape reveal whether the rock cooled inside an underground intrusion or within a volcanic structure? And it eventually helped inspire a very different theory about how the tower formed. In 2015, geologist Prokop Zavada and his colleagues published research proposing another possible origin for Devil's Tower. Instead of treating the monument simply as a stock or volcanic neck, They explored whether it could have formed within a maar-diatreme volcanic system. When hot magma encounters groundwater, the water can heat extremely rapidly. Under the right conditions, that interaction produces explosive expansion and fragmentation of the surrounding material. Such eruptions are called phreatomagmatic eruptions. They can excavate broad craters known as maars, with subsurface structures called diatremes extending beneath them. them. The researchers considered whether magma might have entered a crater or depression associated with this type of volcanic system. The magma could then have solidified into a large mass of rock. The idea was partly inspired by comparisons with a geological formation in the Czech Republic. Researchers examined the orientation and geometry of the columns, along with geological relationships and possible cooling processes. Their study suggested that Devil's Tower could have developed in an environment more complicated than a simple underground intrusion. But there is an important distinction. The 2015 research presented a hypothesis, not a final solution. The complete crater structure and the full sequence of volcanic events have not been established beyond doubt. Still, the study offered another way to interpret the surviving evidence. Different geological processes can produce somewhat similar final landscapes, and when millions of years of erosion have removed crucial evidence, reconstructing the original event becomes extraordinarily difficult. It concerns everything that is missing. Today, Devil's Tower stands high above the surrounding landscape. Its summit is approximately 5,117 feet above sea level and its steep walls make it look like a mountain that has been pushed upward, but the monument's present appearance is largely the result of erosion. These rocks were not equally resistant to weathering. Sandstone, shale and other sedimentary formations could be weakened and gradually removed by flowing water, chemical weathering, temperature changes and physical breakdown. The hard phonolite While porphyry resisted erosion more effectively, rainwater moved across the surface, rivers cut into the landscape, and weathered sediment was transported away, the ground surrounding the igneous body gradually became lower. Eventually, the hardened magma began emerging from the surrounding rock. According to the National Park Service, the processes responsible for exposing the tower began roughly 5 to 10 million years ago. The magma solidified tens of millions of years before the modern tower became visible. The spectacular monument people photograph today is therefore the result of two major geological processes separated by an immense amount of time, then erosion removed the surrounding material. One process created the rock, the other revealed it, but without erosion there might never have been a visible tower at all, and erosion is still changing the landscape today. But some of the best evidence of the monument's continuing geological history lies much closer to the ground. Around the base are extensive deposits of broken rock. Geologists call this material talus. Some fragments are small enough to hold, while others are enormous sections of columns that separated from the tower at some point in the past. Then, though phonolite porphyry resists erosion better than the surrounding sedimentary rocks, its exposed surface is constantly affected by weathering. Water enters fractures between columns. During freezing conditions, water trapped inside cracks can contribute to mechanical weathering as it freezes and expands. Over long periods these processes can weaken sections of rock. The National Park Service reports that small rocks fall from Devil's Tower regularly, although no major column fall has been witnessed in recorded history. The large blocks around its base reveal that substantial failures occurred sometime in the past. The monument is still changing, even if most changes happen far too slowly for a visitor to notice. Meanwhile, rain and rivers continue eroding the surrounding sedimentary landscape. The Belle Fourche River transports material away from the area, helping shape the valley that makes the tower appear so prominent. The landscape surrounding Devil's Tower continues to erode. The same geological forces that helped expose the monument will continue modifying it far into the future. Devils Tower may look completely isolated, but it isn't the only unusual igneous formation in this part of Wyoming. Several miles to the northwest stand the Little Missouri Buttes. These smaller formations are composed of related igneous rock, and are generally considered part of the broader magmatic history of the region. Devil's Tower was not necessarily the result of a completely isolated magmatic event. During the geological period when these intrusions developed, magma was moving through portions of the regional crust. Some may have formed narrow conduits. Still others could have solidified in larger, irregular underground masses. The visible separation between Devil's Tower and the Little Missouri Buttes today may not fully represent the arrangement of magma beneath the ancient landscape. However, similar rock composition does not automatically prove that these formations were physically connected underground. Even without a demonstrated connection, the nearby buttes help scientists place Devil's Tower within a broader geological setting. The Tower may be extraordinary in appearance, but the magma responsible for it was part of a larger chapter. In the history of Northeastern Wyoming, after all these investigations, it might seem surprising that the original shape of Devil's Tower remains uncertain. Scientists know what the rock is made of. They have studied the surrounding sedimentary formations and identified the role of erosion. So why can't they simply determine whether the tower was once a volcanic neck, a stock, or part of a larger intrusion, the difficulty lies in the evidence that no longer exists. You might identify the materials used to construct it and understand how those materials were arranged. Geologists face a similar challenge at Devil's Tower. The surviving rock provides direct evidence of magma crystallization and cooling, but erosion has removed much of the original setting. A volcanic cone, if one existed, may have disappeared. Contacts between different geological units may be concealed underground or no longer preserved. Researchers can examine fractures, analyse minerals, compare the rock with nearby intrusions, and use geophysical methods to investigate what lies beneath the surface. Each technique contributes another piece of information, This is why scientific papers often present interpretations rather than absolute conclusions. A theory becomes more convincing when it explains multiple independent observations and survives attempts to test it. For Devil's Tower, the central facts are well established, but the precise emplacement mechanism is still discussed. There has been no universally accepted discovery proving that one of the competing models explains every feature of the formation. It reveals how much geological history can be lost while the rocks themselves survive. Long before modern geologists began investigating Devil's Tower, the formation was already an important place for indigenous communities. Many Native American nations maintain cultural and spiritual connections with the monument. Traditional names associated with the site include Bear Lodge and Bear's Teepee, reflecting histories and relationships that extend far beyond geological classification. In 1906, President Theodore Roosevelt designated Devil's Tower as the first national monument in the United States. Its protection helped Preserve a landscape that combines extraordinary natural features with deep cultural significance. Yet standing beneath the formation creates an almost misleading impression. The giant pillars seem strong enough to survive unchanged forever, but the tower itself is only a temporary stage in an extremely long geological process. Its surrounding rocks were gradually removed, and weathering continues to reshape the formation. The original magma body may have extended deeper, wider, or in a different direction than the visible structure suggests. That is what makes Devil's Tower such an extraordinary geological landmark. They are looking at what remains after tens of millions of years of geological change. And that brings us back to the question that has fascinated researchers for generations. The clearest answer is that it is an ancient body of phonolite porphyry formed from molten rock and eventually exposed through erosion. Its giant columns are cooling fractures preserved in the hardened magma, but whether the original magma formed a small stock, part of a laccolith, a volcanic conduit, or a more complicated volcanic structure remains an open geological question. The mystery isn't whether the rock came from magma. The mystery is what the original formation looked like before the surrounding landscape disappeared. And perhaps the most remarkable thing about Devil's Tower is that the answer may not be hidden inside the mountain. It may have been carried away one grain of sediment at a time by millions of years of erosion. What remains today is an enormous natural record of a geological event whose complete history has not yet been recovered.