In flight fragmentation reduces bomb size range and hazard during explosive volcanic eruptions

The dataset contains both automatic and manual image analyses of four videos: from  (i) fountaining and (ii) spattering activities at the 2021 Tajogaite eruption of Cumbre Vieja volcano, La Palma, Canary Islands, Spain; from the 2021 Mount Etna eruption (iii) fountaining activity, Sicily, Italy); and from Strombolian activity (iv) in 2023 at Stromboli, Aeolian Islands, Italy.

This dataset consists of one MATLAB file and 15 CSV files. Fourteen CSV files are named according to the case studies  (e.g., T. fountaining, T. spattering, E. fountaining, S. Strombolian), the acquisition mode (Manual or Automatic), the data type (e.g., Collision, Fragmenting, Non-Fragmenting, Total), and specific case details. Notably, the "T.spattering_Manual_Collision" files are split into two categories (e.g., coarser, finer) based on bomb size classification of the colliding-pairs. Additionally, the "E. fountaining_Manual_Collision / Fragmentation" dataset is divided into two regions of interest (ROI1 and ROI2) to reflect separate analyzed areas described in the manuscript. The 15th CSV file, “FragmentingModes_All.csv”, aggregates bomb counts by fragmenting mode across all case studies and corresponds to Figure 3 in the manuscript.

Automated analyses were performed on five different frames: four used for measuring bomb velocity and size (saved in the MATLAB file “Fourframes.mat”), and a fifth frame used for measuring bombs velocity, size, and circularity (saved in the CSV files). The MATLAB file contains four matrices, named according to the case studies (e.g., T. fountaining, T. spattering, E. fountaining, S. Strombolian). Each matrix is composed of two columns: the first for velocity and the second for bomb size. The fifth frame’s data is saved in four separate CSV files for each case study, named as “namecasestudies_Auto_Total.csv”, where “namecasestudies” changes to reflect the specific case studies analyzed. Each CSV includes three columns: velocity, bomb size, and bomb circularity respectively.

Manual data collected in .csv files include the velocity, size and circularity and additional parameters such as: area, position, major axis and minor axis. In the “Fragmenting” files additional fields detail the fragmenting mode, the number of pyroclasts generated, and the fragmentation direction (upward, transitional, or downward). In the “Collision” files an additional field includes the number of pyroclasts produced.

The dataset is graphically represented in the manuscript, particularly in Figures 4,5, 6, and 7.