In a new study, published in the journal Nature, an international team of scientists provides the first conclusive evidence directly linking deep Earth’s water cycle and its expressions with magmatic productivity and earthquake activity.
Water (H2O) and other volatiles (e.g. CO2 and sulfur) that are cycled through the deep Earth have played a key role in the evolution of our planet, including in the formation of continents, the onset of life, the concentration of mineral resources, and the distribution of volcanoes and earthquakes.
Subduction zones, where tectonic plates converge and one plate sinks beneath another, are the most important parts of the cycle — with large volumes of water going in and coming out, mainly through volcanic eruptions. Yet, just how (and how much) water is transported via subduction, and its effect on natural hazards and the formation of natural resources, has historically been poorly understood.
Lead author of the study, Dr. George Cooper, Honorary Research Fellow at the University of Bristol ’s School of Earth Sciences, said: “As plates journey from where they are first made at mid-ocean ridges to subduction zones, seawater enters the rocks through cracks, faults and by binding to minerals. Upon reaching a subduction zone, the sinking plate heats up and gets squeezed, resulting in the gradual release of some or all of its water. As water is released it lowers the melting point of the surrounding rocks and generates magma. This magma is buoyant and moves upwards, ultimately leading to eruptions in the overlying volcanic arc. These eruptions are potentially explosive because of the volatiles contained in the melt. The same process can trigger earthquakes and may affect key properties such as their magnitude and whether they trigger tsunamis or not.”