Oldest description of a caldera-forming eruption in Southeast Asia unveiled in forgotten written sources

As one of the most powerful volcanic events of the Holocene era with a Volcanic Explosivity Index of seven, the 1257 CE eruption of Samalas volcano in the Rinjani Volcanic Complex had large consequences for Lombok Island (Indonesia) and its surrounding area. This huge eruption with an enormous volume of ejected material (4435 ± 5.5 × 106 m3), was recorded in local written sources, called Babad, that were compiled around the sixteenth century and contain oral stories and myths. In this study, we present two written sources, namely Babad Lombok and Babad Suwung, which undoubtedly refer to the 1257 CE ultraplinian eruption of Samalas volcano. In addition to detailed analysis of the volcanic deposits, interviews with old Javanese linguists and museum employees were carried out to clarify the meanings of some words as well as the genesis of the Babads. The results from field observation and interviews were analyzed and compared with previous research. Babad Lombok describes the process of the Samalas eruption, the formation of the Segara Anak caldera, and the impacts of the voluminous ash fall and pyroclastic flows on Lombok Island. Meanwhile, Babad Suwung describes the impacts of the 1257 CE volcanic eruption on Talkuwang (Taliwang), on the western coast of Sumbawa Island. This description encompasses several volcanic processes including fallout and pyroclastic surges. The exegesis of Babad Lombok and Babad Suwung could be the oldest observations of a caldera-forming eruption in Southeast Asia. They also document the oldest pyroclastic surges in the world after those of Vesuvius as described by Pliny the Younger in 79 CE.