The high elevation of parts of the western United States could be a result of water percolating up from deep in Earth's crust, and changing the crust's mineral composition, making the rocks more buoyant.

Geologists have been hard-pressed to explain why Colorado and much of Wyoming have lifted by more than 2 kilometres over the past 75 million years. A team led by Craig Jones at the University of Colorado Boulder reanalysed data on the geology and seismology of the region and conclude that in lower regions, such as Montana, fragments of crustal rock contain dense minerals such as garnet. Beneath high-elevation areas, however, the rocks contain a different suite of less dense minerals. The authors suggest that these were produced by water reacting with the dense minerals and so making the crust lighter.

The water may have come from the dehydration of a deeply buried, ancient crustal slab.

Geology http://doi.org/2ps (2015)