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The article discusses geophysics research by N. Schmerr and colleagues within the issue. The author presents a brief overview of the theory of plate tectonics which posits that horizontal plates below the Pacific Ocean are moving laterally at a rate of approximately 10 centimeters (cm) per year above a weak layer called the asthenosphere. He notes that scientists are puzzled by how the plates, which are as large as 10 thousand kilometers (km), can maintain their rigidity while causing earthquakes at their edges. Topics include the use of high-resolution seismic maps by Schmerr's team to observe the process of plate tectonics, the role of the asthenosphere, which is a viscous layer below the lithosphere, in plate movement, and a diagram illustrating plate tectonics in the ocean.

The permeability of the upper mantle controls melt segregation beneath spreading centers. Reconciling contradictory geochemical and geophysical observations at ocean ridges requires a better understanding of transport properties in partially molten rocks. Using x-ray synchrotron microtomography, we obtained three-dimensional data on melt distribution for mantle peridotite with various melt fractions. At melt fractions as low as 0.02, triple junctions along grain edges dominated the melt network; there was no evidence of an abrupt change in the fundamental character of melt extraction as melt fraction increased to 0.2. The porosity of the partially molten region beneath ocean ridges is therefore controlled by a balance between viscous compaction and melting rate, not by a change in melt topology. [ABSTRACT FROM AUTHOR]

The article discusses the use of precision isotope analysis to reveal details about the dynamic processes involved in the formation of planet Earth's mantle. Topics include a belief among geologists that evidence of the first few hundred million years of Earth's history had been erased by mantle convection and plate tectonics, a study within the issue regarding geophysics research by M. Touboul and colleagues reporting measurements of the isotopic composition of tungsten (W) in 2.8-billion-year-old basaltic rock, called komatiite, which is known to be derived from source regions deep within Earth's mantle, and the abundance of an tungsten isotope 182W, which forms from the decay of an isotope of hafnium (182Hf).

The article discusses a report within the issue regarding geophysics research investigating global plate tectonics. A brief overview of how convention within planet Earth's mantle affects geological activity, such as tectonic motions on the surface of Earth, is presented. Topics include an overview of plate tectonics and the team's creation of a numerical model, which uses adaptive mesh refinement algorithms on parallel computers to observe global mantle flows through simulation methods, and the behavioral influence of the oceanic lithosphere on plate driving forces.