The Central Andes is a key global location to study the enigmatic relation between volcanism and plutonism because it has been the site of large ignim briteforming eruptions during the past several million years and currently hosts the world's largest zone of silicic partial melt in the form of the Alti plano Puna Magma (or Mush) Body (APMB) and the Southern Puna Magma Body (SPMB). In this themed issue, results from the recently completed PLUTONS project are synthesized. This project focused an interdisciplinary study on two regions of largescale surface uplift that have been found to represent ongoing movement of magmatic fluids in the middle to upper crust. The loca tions are Uturuncu in Bolivia near the center of the APMB and Lazufre on the Chile Argentina border, on the edge of the SPMB. These studies use a suite of geological, geochemical, geophysical (seismology, gravity, surface defor ma tion, and electromagnetic methods), petrological, and geomorphological techniques with numerical modeling to infer the subsurface distribution, quantity, and movements of magmatic fluids, as well as the past history of eruptions. Both Uturuncu and Lazufre show separate geophysical anomalies in the upper, middle, and lower crust (e.g., low seismic velocity, low resistiv ity, etc.) indicating multiple distinct reservoirs of magma and/or hydrothermal fluids with different physical properties. The characteristics of the geophysical anomalies differ somewhat depending on the technique used-reflecting the different sensitivity of each method to subsurface melt (or fluid) of different compositions, connectivity, and volatile content and highlight the need for integrated, multidisciplinary studies. While the PLUTONS project has led to significant progress, many unresolved issues remain and new questions have been raised.

The vertical transport of large volumes of silicic magma, which drives volcanic eruptions and the long‐term compositional evolution of the continental crust, is a highly debated problem. In recent years, dyking has been favored as the main ascent mechanism, but the structural connection between a distributed configuration of melt‐filled pores in the source region and shallow magma reservoirs remains unsolved. In the Central Andes, inversion of a new high‐resolution Bouguer anomaly data over the Altiplano‐Puna Magma Body (APMB) reveals ~15 km wide, vertically elongated, low‐density, 3D structures rooted at the top of the APMB at 20 km depth. We integrate our gravity inversion with the available geophysical, geological, and petrological observations, and in agreement with petrological/mechanical considerations propose that, in this region of the Andes, partially molten granitic bodies ascend diapirically through the hot ductile mid‐upper crust.

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[1] Remarkable evidence of coupling between tectonic and magmatic events emerges from investigation of three tectonic earthquakes, aftershock sequences and eruption of Cerro Negro volcano, Nicaragua in 1999. Here, we explain this coupling through static stress changes following three Mw 5.2 earthquakes. We use focal mechanism solutions to estimate fault system geometry and magnitude of slip from these events, which are then used to calculate the change in minimum horizontal principal stress (s 3 ) for the region and the change in Coulomb failure stress on optimally oriented fault planes. Results of these simulations indicate that s 3 was reduced by $0.08 MPa and that Coulomb failure stress was raised by 0.001 to 0.2 MPa in the region. A Kolmogorov-Smirnov test demonstrates spatial correlation of Coulomb failure stress changes and triggered seismicity and volcanism, and suggests that these small changes in static stress can trigger subsequent geophysical events under appropriate circumstances. Citation: Díez, M., P. C. La

Magma is transported through Earth's solid crust by two different processes, diking and diapirism, although other mechanisms, such as porous and channeled fl ow, can transport melt through partially molten crustal areas. Dikes are ubiquitous indicators of the transport of magma in the shallow crust by brittle fracture, and there is ample geological and geophysical evidence supporting diking as a magmaascent mechanism through the crust. On the other hand, igneous diapirism, involving magma ascent by gravitational instability and requiring viscous or plastic fl ow of country rock ("hot Stokes" diapirs), is often invoked as a magma-transport mechanism restricted to the ductile upper mantle or lower crust. However, unequivocal geological fi eld evidence for igneous diapirism has proven elusive and has been a matter of considerable debate. We report geological and geophysical evidence showing that Pliocene sills emplaced in the upper levels of brittle continental crust of the Colorado Plateau in the San Rafael subvolcanic fi eld (Utah) became gravitationally unstable by mechanically altering the overlying sedimentary rocks. These sills grew into structures that we recognize as domes and plugs at the current level of exposure. Some of these plugs continued to transport magma to shallower levels of the continental crust and eventually acted as conduits feeding volcanic eruptions. Our geological and geophysical fi ndings indicate that gravitational instability is a viable mechanism for the initiation of magma ascent in the upper continental crust for small volumes of basaltic magma under specifi c conditions.