Although gas exsolution is a major driving force behind explosive volcanic eruptions, viscosity is critical in controlling the escape of bubbles and switching between explosive and effusive behavior. Temperature and composition control melt viscosity, but crystallization above a critical volume (>30 volume %) can lock up the magma, triggering an explosion. Here, we present an alternative to this well-established paradigm by showing how an unexpectedly small volume of nano-sized crystals can cause a disproportionate increase in magma viscosity. Our in situ observations on a basaltic melt, rheological measurements in an analog system, and modeling demonstrate how just a few volume % of nanolites results in a marked increase in viscosity above the critical value needed for explosive fragmentation, even for a low-viscosity melt. Images of nanolites from low-viscosity explosive eruptions and an experimentally produced basaltic pumice show syn-eruptive growth, possibly nucleating a high bubble number density.

尽管气体逸出是爆炸性火山爆发的主要推动力，但黏度对于控制气泡逸出以及在爆炸性和喷射性之间切换至关重要。温度和成分控制熔体粘度，但超过临界体积（> 30体积％）的结晶会锁定岩浆，引发爆炸。在这里，我们通过显示出意想不到的小体积纳米尺寸晶体如何引起岩浆粘度不成比例的增加，提出了这种公认的范例的替代方法。我们对玄武岩熔体的原位观察，在模拟系统中的流变学测量和建模表明，即使对于低粘度熔体，仅少量体积百分比的纳米晶也会导致粘度显着增加，超过爆炸碎裂所需的临界值。 。