Rocks in Earth's middle mantle flow very slowly, at rates of only a few millimeters per year. This slow flow is important because it helps to drive plate tectonics and other geological processes. However, the mechanisms that cause rocks in the middle mantle to flow so slowly have been poorly understood.

A new study by researchers at the University of California, Berkeley, has shed light on this mystery. The researchers found that the rocks in the middle mantle are very strong and that they only flow when they are subjected to very high stresses. These high stresses are caused by the weight of the rocks above the middle mantle and by the movement of the tectonic plates.

The researchers also found that the flow of rocks in the middle mantle is affected by the temperature and composition of the rocks. The hotter the rocks, the more easily they flow. The composition of the rocks also plays a role, with some types of rocks being more likely to flow than others.

The findings of this study provide new insights into the mechanics of rock flow in the middle mantle. This knowledge could help to improve our understanding of plate tectonics and other geological processes.

Source:

* "Why rocks flow slowly in Earth's middle mantle" by Jessica L. Warren and Nicholas J. van der Meer, published in _Nature Geoscience_.