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A large proportion of the magmas erupted at continental arc volcanoes are andesites, which are regarded as a major component in the formation of continental crust — consequently, it is important to understand andesite petrogenesis. Here, an alternative view of andesite petrogenesis is presented, based on a review of quenched glassy melt inclusions trapped in phenocrysts, whole-rock chemistry, and high-pressure and high-temperature experiments; this new view resolves several puzzling aspects of arc volcanism.

In mature continental rifts, magma intrusion appears to accommodate significant crustal extension. Here, radiometric ages for lavas suggest that this style of focused magmatic accretion and rifting remained stable in the Ethiopian crust for at least ~200 kyr, prior to the onset of true oceanic spreading.

Serpentine subducted below the Lesser Antilles volcanic arc supplies water to the arc, controlling the location of seismicity, volcanic productivity and thickness of crust.

Titanium concentrations in zircon crystals reveal a link between the world’s largest copper resources and magmas with very high-water contents.

Lavas erupted from individual volcanic centres often have one of two distinct compositions. High pressure and temperature experiments on lava samples collected from St Vincent Volcano in the Caribbean, combined with thermal modelling, show that this compositional bimodality is generated by volcanic systems with low heat and water content.

Past volcanic eruptions along the densely populated Ethiopian Rift valley remain poorly constrained despite the present day hazard. Hutchison et al. show that a large volcanic flare up along a 200 km section of the rift occurred between 320–170 ka dramatically affecting the landscape and hominin population.

The global frequency of volcanic eruptions is inversely proportional to the volume of magma erupted in a single event. Numerical modelling of magma reservoirs evolving in Earth’s crust shows that frequent, small eruptions are triggered by injections of magma into the reservoir, but rare, giant supervolcano eruptions are triggered by magma buoyancy.

Imaging of the mantle transition zone beneath the Lesser Antilles shows a basalt-rich region within the subducting slab near the proposed location of a subducted extinct spreading ridge, implying ancient tectonics play a role in influencing slab trajectories.

Most of the world’s copper comes from porphyry ore deposits. Laboratory experiments suggest that these deposits form in a two-stage process over thousands of years, from the interaction between sulphur-rich gases and metal-rich brines.

Seismic imaging of subducted plates offers a way to improve plate tectonic reconstructions. Here, Braszus et al. use new ocean-bottom seismometer data from the Lesser Antilles to locate subducted spreading centres and faults thus providing a new understanding of the evolution of the Caribbean plate.