More than 14,000 Icelanders emigrated to North America between 1870 and 1914 CE. Mass movement from Iceland accelerated the year after the explosive eruption of Askja in 1875, and both contemporary and recent commentators have linked the two circumstances. Despite an abundant scholarship on Icelandic emigration in this period, the direct and indirect roles of the eruption as a possible stimulus remain unclear. Here, we engage critically with a range of contemporary source materials as well as meteorological and climatological information to re-assess where Askja fits into the picture of Iceland's first wave of mass migration. We find that emigration was undoubtedly fuelled by the hardships of Icelanders and their growing contacts with countrymen already in the Americas, and that the highest proportions of emigrants came from counties most directly impacted by the Askja eruption. However, it also emerges that the eruption served as a lever for interested parties in Britain and Canada to persuade large numbers of desirable migrants to settle in North America. Our study highlights the opportunities that discrete episodes of volcanic activity present to probe the complex interrelationships of nature and society.