On 3 June 1991, a deadly cloud of hot gas and rock spewed out of Japan’s Mount Unzen. Among the 43 people consumed by it were scientist-filmmakers Maurice and Katia Krafft. They left behind over 200 hours of footage from their decades of work, which Herzog draws on for this stunning eulogy. From 1977’s La Soufrière through to 2016’s Into the Inferno, Herzog has long been fascinated by these violent natural events and his deeply personal voiceover is a fitting memorial to two people who gave their lives in the pursuit of both science and the pure cinematic image.