Dating young lava flows is essential for understanding volcano’s eruption frequency, yet challenging due to methodological limitations of commonly used dating techniques. Ruapehu (Aotearoa New Zealand) has produced many lava flows during the Holocene, but constraints on the timing of these eruptions are scarce. Here, we combine paleomagnetic dating and relative stratigraphy to deliver new eruption ages of 18 lava flows with low-to-high error window ranges between 500 and 2700 years (at the 95% confidence level). Our data indicate that the large lava flow field located on the Whakapapa area (northwest Ruapehu) was emplaced during at least three distinct eruptive episodes between 10.6 and 7.4 ka. Two of these episodes closely followed a large collapse event that affected Ruapehu’s northern edifice, and generated large volumes of lava between 10.6 and 8.8 ka, with the third episode producing less voluminous lava flows between 8.1 and 7.4 ka. Following a smaller collapse of the southeastern sector of the edifice at ca. 5.3 ka, several low-volume lava flows were emplaced during at least two distinct eruptive episodes prior to ca. 1.0 ka, which supplied the Whangaehu valley (east Ruapehu) with lava. The youngest age inferred from our data represents the youngest eruption age provided for a lava flow outside Ruapehu’s summit region. This research provides greater detail to the Holocene effusive chronology at Ruapehu, shedding light on partial cone reconstructions after edifice collapses during the early and late Holocene, and the time relationships between trends observed in its effusive and explosive activity.

Volcanic meteo-tsunamis, though rare, can pose significant threats to people, as exemplified by the 2022 Hunga Tonga – Hunga Ha’apai (HT-HH) eruption in the SW Pacific. While various studies have delved into the complexities of such phenomena, none have explored analogous scenarios in regions with potential occurrence of large eruptions near or under the sea. We focus on coastal areas along the South China Sea (SCS), among the most densely populated on Earth and historically prone to volcanic activity, including the catastrophic 1883 Krakatau eruption. Here we strategically chose one intra-basin volcano, KW-23612 in the northern SCS, and three extra-basin volcanoes, Banua Wuhu in the Celebes Sea, and Kikai and Fukutoku-Oka-no-Ba in the northern Philippines Sea (southern Japan), from which we simulated volcanic meteo-tsunamis with scaled intensities of the HT-HH event, to assess which countries around the SCS could be more at risk from the occurrence of such phenomena. Our results show that the worst-case scenarios are produced by eruption/tsunamis from the northern SCS, producing offshore waves up to 10 cm offshore Macau and Hong Kong, and up to 20 cm offshore Manila. In contrast, countries bordering the shallow Sunda Shelf (Malaysia, Thailand, Cambodia, and southern Vietnam) seem less at risk from volcanic meteo-tsunamis, though we observed some amplification effects along the deeper Singapore Strait. This study is the first of its kind in the region and sets the basis to investigate amplification effects, and shallow coastal dynamics at key locations, after integrating higher resolution bathymetry data.