Crowdsourcing human observations expands and enhances volcano monitoring records

Volcano monitoring is constrained by the distribution of sensors that record activity. Here, we explore the role of crowdsourcing to broaden acoustic monitoring records by surveying people across Aotearoa New Zealand about the sounds they heard following the 2022 climactic eruption of Hunga volcano in Tonga. We compare the 1930 survey responses to geophysical records of the pressure waves and find that they align well, both recording ~5-7 audible signals of varying amplitude with a peak of 60-80 decibels, arriving in two 30-minute phases ~3 hours post-eruption, travelling North-to-South. The crowdsourced observations fill instrumental gaps regarding the wave’s audible frequencies and contribute insights into interactions between the far-field acoustic wave and the social and built environment. Descriptions of short-lived impacts reveal that pressure waves are capable of substantial disturbances thousands of kilometers from the vent. We demonstrate that crowdsourcing can support traditional monitoring as a reliable low-cost method to capture perishable data.