Heart Mountain in Wyoming, United States, has been extensively studied, because Ordovician age carbonates (Madison Limestone), sit on top of a much younger (~50Ma) sedimentary formation (Willwood Formation). It is now largely accepted that this juxtaposition of old rocks on top of young is the result of gravity spreading and gliding. Field observations, such as slight internal deformations of the older formation, indicate the gravity gliding and spreading of the Madison Limestones. The specific details of the gravity spreading event are unclear, but it is thought that it was induced by the Laramide Orogeny, approximately 50 Ma. This caused the Madison Limestones to slide into the nearby Bighorn Basin, where it came to rest on top of the Willwood Formation. The cause for block motion is debated, with numerous models to explain how such a large block could have moved tens of kilometers down a slope of less than 2°. Models have ranged from lubrication by hydrothermal circulation, movement initiation from volcanogenic seismicity, to frictional heating dissociating CO2 from the carbonates, resulting in dramatically reduced friction. The last of these theories is among the most recent, and by far the most spectacular. The authors envisage initially slow sliding, likely as the result of a volcanic eruption, until frictional heating of the carbonate rocks creates a supercritical CO2 layer, decreasing the friction tremendously. From this point, the sliding would occur rapidly, perhaps as high as 150 km/h.