Scientists Just Revealed What's Hidden Beneath Colorado... And It's Terrifying

Right now, deep beneath the Colorado Rockies, the ground is still rising, splitting, and sliding. A supervolcano once erupted here with a force thousands of times greater than Mount St. Helens. A mountainside near Lake City is creeping downhill as you read this. And in the 1960s, the US military accidentally triggered a swarm of earthquakes beneath the city of Denver, from a billion-year-old canyon to the tallest sand dunes in North America. The Mountains That Rose Inland The Rocky Mountains are one of North America's defining landmarks. But geologists have spent decades trying to explain exactly how they formed. Most great mountain ranges rise where tectonic plates collide. The Rockies are different. They rose hundreds of miles inland, far from any active plate boundary. Around 70 million years ago, an oceanic plate is believed to have slid beneath North America at an unusually shallow angle. Instead of plunging deep into the mantle, it scraped almost horizontally beneath the continent. The crust responded violently. Rock layers folded. Faults broke. Entire blocks of land were forced upward. Over millions of years, Colorado's mountains emerged from what had once been a much flatter landscape. Even today, scientists continue debating the details. One of the continent's most famous mountain ranges remains one of geology's greatest mysteries. Mountains Before The Mountains The Rocky Mountains may define Colorado today, but they were not the state's first mountains. Roughly 300 million years ago, another mountain range dominated the region. Geologists call them the Ancestral Rockies. Entire mountains were reduced to sand, gravel, and mud. Rivers carried those sediments across vast distances, where they accumulated layer by layer. Over time, the deposits hardened into stone. For millions of years, they remained buried and largely forgotten. Then, Colorado's modern mountains began to rise. The forces that created the Rockies pushed and tilted those ancient rock layers upward. What had once been flat sediment became towering walls of stone. Today, those remains form some of Colorado's most famous landscapes. Garden of the Gods, the Flatirons above Boulder, the towering red cliffs of Red Rocks Amphitheatre. Massive slabs of sandstone now stand nearly vertical, slicing into the sky like the fins of some enormous buried creature. The irony is remarkable. Some of Colorado's most iconic scenery is actually the graveyard of a mountain range that vanished hundreds of millions of years ago. The mountains we admire today were built, in part, from the remains of mountains that came before them. The Continent Pulling Apart Most people imagine continents as solid and permanent. They aren't. Beneath Colorado's San Luis Valley lies the Rio Grande Rift, one of North America's largest active fracture systems. For millions of years, forces deep within the earth have been reshaping this region. Faults slip, the valley floor slowly sinks, and pathways open for heat rising from below. The changes are almost impossible to notice in a human lifetime. Yet, they never stop. Standing in the San Luis Valley means standing on a landscape that is still under construction. The Earthquakes We Caused Earthquakes are supposed to be natural disasters. Colorado helped prove they don't have to be. In the 1960s, toxic wastewater from military operations was pumped deep underground at the Rocky Mountain Arsenal near Denver. Not long afterward, earthquakes began shaking the area. The injected fluids increased pressure along ancient faults buried beneath the region. Faults that had remained locked for thousands of years suddenly began to move. The result was one of the first clear demonstrations that human activity could trigger earthquakes. The discovery changed geology forever. Today, similar injection-related earthquakes have been documented around the world. But one of the earliest warnings came from beneath Colorado. The unsettling lesson was simple. Sometimes, the ground only needs a small push. Colorado's Youngest Volcano When most people think of Colorado, volcanoes rarely come to mind. Yet the state's volcanic story is far from over. Near the town of Dotsoro sits Colorado's youngest volcano. It erupted only about 4,000 years ago, practically yesterday in geological terms. The eruption began when rising magma encountered groundwater trapped beneath the surface. The water instantly flashed into steam. Pressure built rapidly. Then, the ground exploded. The blast carved out a broad crater known as a mar, which remains visible today. Colorado's volcanic past is far younger than most people realize. The Spanish Peaks and Their Dykes Rising dramatically above the southern plains are the Spanish Peaks. At first glance, they appear to be ordinary mountains. They aren't. The peaks are remnants of ancient volcanic activity. But the most remarkable features are the giant walls of rock extending outward from them. These formations are called dykes. Millions of years ago, molten rock forced its way into underground fractures. The magma cooled and hardened. Later, erosion stripped away the softer rock around it. What remained were enormous stone walls radiating outward across the landscape. Seen from above, they resemble the spokes of a giant wheel. Few places on Earth reveal the hidden plumbing of an ancient volcano so clearly. The Black Canyon of Deep Time At first glance, the Black Canyon of the Gunnarsson looks impossible. Its walls plunge nearly straight downward into darkness. Some sections are so narrow that sunlight reaches the bottom for only a few minutes each day. That darkness is what gave the canyon its name. But the real story lies in the rock itself. At the bottom of the canyon are some of the oldest exposed rocks in North America, around 1.7 billion years old. When these rocks formed, complex life had not yet appeared on Earth. For immense spans of time, these ancient rocks remained buried deep underground. Then the Gunnarsson River began cutting downward, slowly, relentlessly. Over millions of years, it carved through the landscape and exposed a chapter of Earth's history normally hidden far beneath our feet. Towering above the canyon is the Painted Wall, the tallest sheer cliff in Colorado. Dark volcanic rock dominates its face, while pale pink bands slice through it like giant brushstrokes. Those streaks formed when molten rock forced its way into fractures more than a billion years ago. The magma cooled underground and remained hidden until erosion revealed it. Today, the cliff rises more than 2,000 feet above the canyon floor, like a giant stone fortress. Few places on Earth allow you to see nearly 2 billion years of geological history exposed in a single landscape. The Royal Gorge West of Canyon City, the Arkansas River cuts through a deep chasm known as the Royal Gorge. Its granite walls rise more than 1,000 feet above the river below. What makes the gorge remarkable is how it formed. As the rocky mountains slowly rose, the river somehow maintained its course. Instead of being diverted, it carved downward, year after year, century after century, million after million years. The river sliced deeper as the land continued rising around it. The result is one of the most spectacular canyons in the American West. What happened next took millions of years. A river slowly defeated an entire mountain range. The Canyon That Drops Rocks Glenwood Canyon is one of the most beautiful landscapes in Colorado. It is also one of the most dangerous. The canyon's steep walls constantly battle gravity. Rock falls are common. Wildfires weaken slopes. Heavy rain triggers mudslides and debris flows. Massive boulders occasionally crash onto roads and rail lines below. Every year, engineers work to stabilize sections of the canyon. And every year, nature reminds them who is really in charge. Travelers passing through Glenwood Canyon are moving along the floor of a landscape that is actively falling apart. The canyon may look permanent, but it is still being carved, broken, and rebuilt before our eyes. The Tallest Dunes in North America Against the foot of the Sangre de Cristo mountains rises one of the strangest landscapes in America, the Great Sand Dunes. Some tower nearly 750 feet above the valley floor, making them the tallest dunes in North America. The sand originated in ancient lakes and riverbeds left behind after the Ice Age. Over thousands of years, powerful winds pushed those grains across the San Luis Valley. The mountains trapped the sand, preventing it from escaping. Slowly, the dunes grew into a vast sea of sand surrounded by snow-covered peaks. A desert that somehow became stranded in the middle of the Rockies. The Roof of the Rockies Colorado is the highest state in America. More than 50 peaks rise above 14,000 feet. These mountains are known simply as the 14ers. The highest of them all is Mount Elbert, standing 14,440 feet above sea level. At those elevations, the air becomes dramatically thinner. Every breath contains less oxygen. Even healthy visitors can quickly find themselves exhausted. Altitude sickness can strike without warning. Headaches, nausea, confusion. In severe cases, fluid can build up in the lungs or brain. Every year, hikers underestimate these mountains. Many are forced to turn back. Some never make it down. The danger isn't always visible. Sometimes, it is simply the air itself. Dinosaur Kingdom Long before Colorado became a land of mountains and ski resorts, it belonged to giants. During the Jurassic period, vast floodplains stretched across much of the region, and those floodplains were filled with dinosaurs. Near Morrison, Dinosaur Ridge preserves enormous footprints left nearly 150 million years ago by animals that vanished long before humans appeared. Colorado also helped launch America's fascination with dinosaurs. Fossils discovered here included famous species such as Stegosaurus, Apatosaurus, and Allosaurus, transforming the state into one of the world's most important dinosaur regions. Elsewhere, Dinosaur National Monument preserves a wall containing more than 1,000 dinosaur bones, many still embedded exactly where they were buried millions of years ago. And in southeastern Colorado, the Picket Wire Canyonlands contain the largest documented dinosaur track site in North America, with more than 1,000 footprints crossing an ancient lakeshore. The dinosaurs vanished, the mountains rose. Entire ecosystems disappeared, yet their tracks and bones remain, preserving a world that once belonged to giants. The Petrified Forest of Florissant West of Pikes Peak stands one of the strangest forests in America. Its trees are made of stone. At Florissant Fossil Beds, giant redwood stumps still stand where they grew millions of years ago. Some measure more than 10 feet across. 34 million years ago, volcanic eruptions devastated the region. Ash and mud buried an entire valley. Normally, the forest would have rotted away. Instead, it was preserved. Minerals slowly replaced the wood, cell by cell, until the trees became solid rock. Today, visitors walk among the remains of a forest that died before humans existed. The trees are gone, their stone ghosts remain. The Vanished Inland Sea Colorado's eastern plains seem about as far from the ocean as a place can be. But, during the age of dinosaurs, much of the state lay beneath a vast inland sea. Known as the Western Interior Seaway, it stretched from the Arctic Ocean to the Gulf of Mexico. For millions of years, giant marine reptiles hunted through warm, tropical waters where cattle now graze. Massive clams rested on the seafloor. Ammonites drifted through the currents. The evidence remains buried beneath the plains. Every farm, highway and grassland stretching across eastern Colorado exists on what was once the bottom of an ancient ocean. The Ice Age Time Capsule In 2010, construction workers near Snowmass Village made an extraordinary discovery. Beneath the ground lay the remains of a lost world. Scientists soon uncovered mammoths, mastodons, giant ground sloths, ancient bison and dozens of other Ice Age animals. The fossils had been preserved within the sediments of an ancient mountain lake. For thousands of years, they remained untouched. The discovery became one of the most important Ice Age fossil finds in North America. For a brief moment, Colorado gave scientists a perfectly preserved window into a world that no longer exists. Colorado's Mineral Wealth Much of Colorado's history was shaped by forces that no longer exist. Millions of years ago, magma rose through the crust beneath large parts of the state. The heat fractured surrounding rock and sent mineral-rich fluids through underground cracks. As those fluids cooled, valuable metals crystallized deep below the surface. Gold, silver, copper, lead, zinc. The result was the Colorado Mineral Belt, one of the richest concentrations of mineral wealth in North America. For millions of years, those resources remained hidden underground. Then, people found them. Mining towns appeared across the mountains as prospectors rushed in search of fortune. Some of the richest discoveries occurred near Cripple Creek, where gold deposits formed around the remains of an ancient volcano. Later, uranium deposits in southwestern Colorado fueled another boom during the Cold War. Colorado's wealth came from deep beneath the earth, and like many treasures, it carried a price. The Creeping Mountain Near the town of Lake City, an entire mountainside is moving. The Slumgullyan Earth Flow is one of the largest active landslides in North America. For centuries, millions of tons of rock and soil have slowly crept downhill. The movement is slow enough for forests to grow on its surface, yet fast enough to tilt and distort the trees themselves. From above, the landscape appears frozen in place. It isn't. The mountain is still flowing like a river of stone. Avalanche Country Colorado's mountains attract millions of visitors every year. But beneath all that beauty lies one of the state's deadliest natural hazards. Avalanches. Every winter, enormous quantities of snow accumulate across the Rockies. Most of the time, the snow remains stable. Sometimes, it doesn't. A weak layer suddenly fails, and an entire mountainside breaks loose. Within seconds, millions of pounds of snow can race downhill at highway speeds. Colorado records more avalanche fatalities than almost any other state in America. The same mountains that inspire adventure can become deadly without warning. The Deadly Bells The Maroon Bells are often called the most photographed mountains in Colorado. Their twin peaks rise above alpine lakes and forests, creating one of the most famous views in the American West. From a distance, they look perfect. Up close, they tell a different story. The mountains are built from weak sedimentary rock that fractures and crumbles with alarming ease. Loose blocks break away unexpectedly. Entire sections of slope can collapse beneath climbers' feet. Over the years, numerous accidents and fatalities have earned them a grim nickname. The Deadly Bells Their stunning beauty masks dangerously unstable rock. And few places capture Colorado's dual nature more perfectly. Beautiful and dangerous. The Mountains That Exploded Today, the San Juan Mountains are among the most beautiful landscapes in North America. Towering peaks, deep valleys, endless forests. But their origins are violent. Millions of years ago, the region was one of the most volcanically active places on the continent. Repeated eruptions buried the landscape beneath lava and ash. Entire mountains formed, collapsed, and formed again. Gigantic magma chambers accumulated beneath the surface. Volcanic activity reshaped the region again and again. The mountains visitors admire today are not simply mountains. They are the surviving fragments of an ancient volcanic kingdom. A landscape built by fire. The Supervolcano of the San Juans Hidden within those mountains, lies the scar of one of the largest volcanic eruptions ever discovered on Earth. Roughly 28 million years ago, an immense magma chamber accumulated beneath southwestern Colorado. For thousands of years, pressure continued building. The molten rock expanded. Gases dissolved within the magma. The crust above slowly weakened. Then, the system failed. The eruption that followed was almost beyond imagination. Vast quantities of magma exploded from the Earth. Pyroclastic flows raced across the landscape. Ash darkened the sky. And when the eruption finally ended, the emptied magma chamber could no longer support the ground above it. The surface collapsed inward. The result became known as the La Garita Caldera. One of the largest volcanic collapse structures ever identified on Earth. Imagine standing in Colorado, as the ground suddenly collapsed into a crater dozens of miles wide. Entire landscapes would have vanished beneath clouds of ash, rock and superheated gas. It was one of the most violent moments in the geological history of North America. The eruption that dwarfs the rest. The La Garita eruption produced a deposit known as the Fish Canyon Tuff. Scientists estimate that roughly 5,000 cubic kilometers of volcanic material erupted during the event. For comparison, Mount St. Helens released less than one cubic kilometer. Thousands of cubic kilometers of magma blasted into the atmosphere. Pyroclastic flows swept across the landscape. Ash darkened the sky over enormous distances. Human civilization has never witnessed an eruption on this scale. Yet Colorado bears the scars of one. The land that never stopped moving. It is tempting to see Colorado's mountains as permanent. But permanence is an illusion. The Rockies are still rising. The Rio Grande Rift is still reshaping the continent. Landslides continue creeping downhill. Avalanches continue remaking mountainsides. And deep underground, the heat that once powered supervolcanoes has never completely disappeared. Tonight, while millions of Coloradans sleep, those forces will continue their work. A mountainside will move. A fault will accumulate stress. A river will carve its canyon a little deeper. Colorado looks timeless. But it is not a landscape frozen in time. It is a geological event still unfolding. And that may be the most unsettling fact of all.