In northwestern Wyoming rises Heart Mountain, a rock formation that puzzled the scientific community for more than a century. Its summit consists of 500-million-year-old marine limestone strata resting anomalously atop much younger sedimentary rocks, just 50 million years old. Even more unusual: this massive block of rock, with an original extent exceeding 3,400 square kilometers, traveled nearly 50 kilometers from its source across a nearly horizontal slope of just two degrees.
Classical laws of rock mechanics and friction dictated that moving such a mass over virtually flat terrain was impossible without disintegrating the structure. However, recent geological research has solved the enigma by uncovering an extreme phenomenon known as frictional decarbonation:
- The magmatic trigger: About 48 million years ago, volcanic activity in the Absaroka field and a series of mega-earthquakes fractured the Earth's crust.
- A chemical reactor beneath the rock: Initial friction between the layers generated frictional temperatures exceeding 800 °C, causing the calcium carbonate at the base to decompose instantly into calcium oxide and copious amounts of carbon dioxide gas.
- Hovercraft effect: Unable to escape, the gas compressed under extreme pressures lifted the gigantic block, virtually eliminating all friction and allowing the mountain to slide at over 100 km/h in a matter of minutes.
The Heart Mountain cataclysm represents the largest known subaerial landslide on Earth, proving that landforms are not always sculpted over eons, but can sometimes be reconfigured in the blink of an eye.
Source: Journal of Structural Geology / United States Geological Survey (USGS)
