Martin Fisch/Flickr

The Atlas Mountains in Morocco are unusually high, given that they do not have roots that are deep enough to maintain them, according to standard models for mountain formation. However, a team of researchers who measured seismic data found the mountain range is floating on a bed of hot molten rocks which gives them extra buoyancy.

Meghan Miller and Thorsten Becker at the University of Southern California (USC), who published their work in Geology, suggest the layer of molten rocks flows beneath the lithosphere in the region, and may extend from the volcanic Canary Islands just off the western coast of Morocco. According to their model, the hot mantle is rising up and pushing the mountain range from beneath, which explains why the Atlas mountains are unusually high.

“Our findings confirm that mountain structures and their formation are far more complex than previously believed,” said Miller, assistant professor of Earth sciences at the USC Dornsife College of Letters, Arts and Sciences in a press release.

The standard model suggested that the higher mountains are, the deeper the roots they need to support them, similar to how the visible part of an iceberg above water is supported by a large mass of ice beneath the surface. This property is known as “istostacy.”

When the researchers measured the roots of the 4,000 metres high Atlas Mountains, they found them to extend to 35 km into the crust, slightly more than two thirds of what the traditional model predicts.

The researchers found the asthenosphere, which is the layer just below the lithosphere and which contains flowing mantle, was shallow beneath the mountains and pushed upwards when compared to the surrounding region, which the researchers suggest is due to the hot mantle rising up beneath the mountains.