Seamounts (Global, ≥1000 m prominence)

When data quality and completeness allow, likely in the mid-2030s, we will begin a full global analysis of seamounts with ≥1000 metres of topographic prominence. This will form the final part of the Ribus trilogy.

A first-order estimate of the global total is already possible. Based on the oceans covering ~71% of Earth’s surface, and with 7,151 terrestrial Ribus identified, a simple scaling suggests on the order of ~15,000 submarine equivalents. This figure has recently received striking independent support from the study A Global Dataset of Bathymetric Features Identified with Prominence and Isobaths Analysis (Souche et al., 2026), which identifies 15,204 seamount-like features meeting comparable criteria from the GEBCO 2025 Grid.

This work represents an important and welcome step: a global, reproducible, prominence-based extraction of submarine features at unprecedented scale. However, it remains dependent on the current generation of bathymetric data, which is still uneven in resolution and coverage. As a result, while the overall magnitude is likely close to correct, the precise identification, delineation and validation of individual features will require substantially improved datasets.

Two named examples in British waters help to ground this discussion. The Anton Dohrn Seamount rises to a summit depth of approximately −536 m and has an estimated topographic prominence of 1,477 m. Based on present data, it therefore comfortably qualifies as a submarine Ribu and stands as one of the more substantial and clearly defined isolated features in the region.

By contrast, the Hebrides Terrace Seamount has a summit depth of around −986 m and a prominence of roughly 723 m based on current GEBCO 2025 Grid values. While still a significant structure, it falls below the 1000 m Ribu threshold and would not be included in a global Ribus catalogue.

In this part of the North Atlantic, where bathymetric coverage is relatively dense and high-quality, these figures are unlikely to change dramatically. The greater uncertainties lie elsewhere, in the vast and still sparsely mapped regions of the global ocean, where comparable features may yet shift classification as better data becomes available.

The aim of the Ribus project will be to move beyond automated extraction towards a fully curated and conceptually unified global catalogue of submarine Ribus, comparable in rigour and clarity to those already established for land and other planetary bodies.

Stay tuned.