When magmas remain underground, without erupting, those systems are called plutons. Part of what determines whether those magmas will erupt from plutons is how closely integrated the melt and the crystals are (also called how “mushy” the system is). This collaborative US-Swiss team will integrate field data, laboratory experiments, and computational numerical analysis to develop a model for understanding the physics of plutons and how crystals and melt interact within them. This project supports a team in the US, and a team in Switzerland. The field work, led by the Swiss part of this team, will occur in Adamello, Italy; Spirit Mountain, USA; and the Famatinian arc, Argentina). The Swiss team will look at the geochemistry and microtextures of the rock, and compare them with the experiments and numerical models created by the US team. Developing models to examine how melt and crystals separate in mushes is critical for understanding what leads to volcanic eruptions. The international collaborative nature of this work will provide unique training for the graduate students and postdoctoral scholars involved. Undergraduate Research Experience programs at Brown and MIT will engage even more students in the project. This collaborative U.S.-Swiss project is supported by the U.S. National Science Foundation (NSF) and the Swiss National Science Foundation (SNSF), where NSF funds the U.S. investigator and SNSF funds the partners in Switzerland. While developments in geochemist