Land formations across the West are changing because of the land's own weight, according to a new study by geologists.
Published in the new issue of Nature, the study contradicts the long-held belief that mountains were built and brought down only by tectonic plate activity.Instead, it found parts of the West subjected to high amounts of "gravitational potential energy."
Measurements of sound waves bounced into the Earth's 100-mile-thick crust and upper mantle showed the western United States topography acted as a "viscous" fluid over millions of years.
The gravitational energy locked in the continent has been spreading in places such as the Great Basin of Nevada and western Utah and the Sierra Nevada in eastern California, geologists said.
"The western United States may be the single best example of an area that has deformed much differently than one would expect from traditional plate tectonics," University of Colorado geologist Craig Jones said.
In Colorado, some of the highest amounts of the energy were measured from Leadville south to the San Luis Valley. A large "fault scarp" at the Great Sand Dunes National Monument indicates an earthquake with a magnitude of more than 7 hit the region about 10,000 years ago.
"It looks like gravitational potential energy is trying to drive southern Colorado apart," said Jones, lead researcher in the study.
But more research is needed, he added.
In an accompanying article in the magazine, Philip England of the University of Oxford said the distribution of density inside the continents appears to influence their deformation.
"The continental crust floats on the denser mantle as icebergs float on water," he wrote.
Working with Jones were Jeffrey Unruh of William Lettis and Associates of Walnut Creek, Calif., and Leslie Sonder of Dartmouth University.