The mountains are sitting atop a layer of molten rock that flows beneath the region's lithosphere, perhaps all the way from the volcanic Canary Islands just off northwestern Africa, researchers at the University of Southern California said.
"Our findings confirm that mountain structures and their formation are far more complex than previously believed," lead author and earth science Professor Meghan Miller said.
Currently accepted models for the Earth's lithosphere suggest the height of the Earth's crust must be supported by a commensurate depth, much like how a tall iceberg doesn't simply float on the surface of the water but instead rests on a large submerged mass of ice.
"The Atlas Mountains are at present out of balance, likely due to a confluence of existing lithospheric strength anomalies and deep mantle dynamics," study co-author Thorsten Becker said.
Miller and Becker used seismometers to measure surface vibrations to "see" into the deep subsurface below the mountains.
The crust beneath the Atlas Mountains, which rise to an elevation of more than 13,000 feet, reaches a depth of only about 25 miles, about 9 miles shy of what the traditional model predicts, they said.