The migration of volcanic activity in the Tharsis region of Mars could have been caused by rotation of the planet’s outermost rigid shell relative to its internal layers, according to a study online in Nature Geoscience. The possibility of large-scale horizontal motion of this shell ? which behaves similarly to a single tectonic plate ? has not been previously demonstrated.
Shijie Zhong used three-dimensional numerical models to simulate the slow churning of Mars’s interior in response to the cooling of the planet. The results suggest that a plume of hot material rising through the planet’s interior led to the earliest volcanism in the Tharsis region, simultaneously triggering rotation of the outer shell. As the shell moved southward over the stationary plume ? like a sheet of cardboard over a candle ? it shifted the location of the volcanism.
Although this motion is similar to the movement of a tectonic plate over a plume on Earth, such as the Hawaiian hotspot, Mars is composed of only a single plate that moves as a whole relative to the interior of the planet.