| 16 Jun 2026
The physical and cultural traces of a 19th century volcano-collapse tsunami: New constraints on the magnitude and impacts of the 1888 Ritter Island tsunami, Papua New Guinea
Abstract. The lateral collapse of Ritter Island volcano, Papua New Guinea, on 13th March 1888, generated a devastating tsunami with observed effects at distances of up to 500 km. As the largest recorded volcano lateral collapse, the event is significant in improving our general understanding of volcano instability and associated hazards. Proximal records of the tsunami are limited to post-event reports of extensive coastal damage of nearby islands. Here, we present new field observations of tsunami deposits on these coastlines, supplemented by and interpreted alongside oral accounts from coastal communities (from 2004) and a reanalysis of contemporary reports. Our data reveal the widespread presence of massive and chaotic conglomerates deposited by the tsunami at sites up to 30 km from Ritter, with thicknesses of up to 2.0 m and extending up to 400 m from the shoreline. Such deposits may be indicative of large-magnitude landslide-generated tsunamis, and are generally structureless, coarsest and thickest near the coast, and contain mixed terrigenous and marine clasts, including corals, shells and benthic foraminifera. Isolated large coral blocks are also widespread tsunami inundation markers, reaching >200 m from the shore. The deposits extend to approximately half the maximum inundation distance indicated by oral accounts; the latter preserve precise detail consistent with the timing, spatial characteristics and impacts of the Ritter tsunami interpreted from prior geological surveys, distal accounts and simulations. Collectively, this study indicates that the impacts of the 1888 tsunami on proximal shorelines were larger than has been previously inferred from post-event reports. The maximum run-up height was likely many tens of metres on Sakar and Umboi and extensively exceeded 20 m on western New Britain. From the collated descriptions, we also estimate that ~2000–3000 deaths were caused directly by the tsunami. These new observations add to previous submarine surveys of the event, allowing the coupled process of landslide motion and tsunami generation at Ritter Island to be investigated more comprehensively.
The study focuses on the 1888 lateral collapse of the Ritter Island volcano, which generated a devastating landslide-related tsunami. The authors present new field observations of (relatively) proximal tsunami deposits found up to ca. 30 km from Ritter Island. These geological findings illustrate a greater and more detailed impact than that based on previously known reconstructions. These new data are supplemented by oral histories collected from nearby communities in 2004, based on oral tradition passed down for two-three generations. The integration of geological and anthropological data provides an improved understanding of this catastrophic event. The English is clear and the text reads well.
Major Comments
Reliability of oral accounts: The manuscript utilizes oral accounts shared by coastal communities in 2004. These interviews in my opinion are affected by a significant uncertainty because they were orally transmitted for two-three generations (i.e., ca. 115 years). Figure 6 summarizes all information, but a barplot or a table would be useful to put all sources side-by-side, quantitatively. Have you tried to add an uncertainty buffer to the presented data?
Other landslide-related tsunamis: The authors should consider referencing and discussing other well-documented works on past landslide-related tsunamis. Specifically, drawing comparisons with geological, historical and recent events at Stromboli (Italy) and Kolumbo 1650 (Greece) would provide valuable context.
Small sketches: Studied stratigraphic sections are currently represented using sketches and fence diagrams. The authors should enlarge these sketches significantly to improve legibility, possibly splitting them in more figures and moving the less important ones to Supporting Material.
Campaign photos: Some campaign photos are present but compressed in Figure 2. I suggest showing the photos side-by-side with the related sketches. Moreover, grain-size distributions are graphically reported, but I could not find tabulated percentile values, or at least the median and sorting.
Source island imagery: Figure 1 rightly shows the regional context, including the locations where field surveys and oral accounts were gathered. However, the manuscript notably lacks a dedicated figure or photograph of the source, Ritter island itself, and, possibly, an idea of its shape before and after the catastrophic event.
Discursive Results Section: The Results section is currently written in a highly narrative format. Because of this, it reads more like a "pre-discussion". The authors should make an additional effort to streamline this section a bit more.