The mountains only descend beneath the surface to a depth of 35 kilometers.
The standard model for mountains is that high mountains must have deep roots for support. The Atlas Mountains in Morocco, however, do not have deep roots, a press release obtained by EurekAlert reveals. Instead of being rooted to the ground, the Atlas Mountains are floating on a layer of molten rock. Scientists believe that this molten rock could perhaps originate as far away as the Canary Islands.
The hot magma flows beneath the region’s lithosphere, the outermost layer of the Earth. This is significantly different from typical mountain ranges, where the higher the mountain, the deeper its roots must be beneath the surface in order to support its weight.
“Our findings confirm that mountain structures and their formation are far more complex than previously believed,” said lead author Meghan Miller, assistant professor of Earth sciences at the University of Southern California (USC).
“Istostacy” refers to the concept that height and depth must be compatible in geology, Nature World News explains. A good example of this concept is an iceberg, which does not simply float on water but rather is supported by a large, underwater mass of ice. The imbalance of istostacy in the Atlas Mountains as well as the mantle dynamics mean that the Atlas Mountains are out of balance. The team used seismometers to measure the thickness of the lithosphere, specifically examining the area of the Atlas Mountains in Morocco. In total, they analyzed 67 different seismic events, measured by the 15 seismometers they had placed in the area. By analyzing the vibrations, the scientists were able to determine the thickness of the lithosphere and compare that to the height of the mountains to see whether the height and depth corresponded.
The Atlas Mountains do not have strong structural support underneath them. The mountains only descend beneath the surface to a depth of 35 kilometers. This is about 15 kilometers shy of what traditional modeling tells scientists is necessary in order to support the height of the mountains.
“This study shows that deformation can be observed through the entire lithosphere and contributes to mountain building even far away from plate boundaries,” Miller said.