Methods used to reconstruct the vent geometry via trajectory tracking. (a) ‘Cut-off angle method’ (CAM): by analyzing all straight (unbent) trajectories of high-speed particles, the cut-off angle, i.e., the maximum of all possible ejection angles ε, can be determined and used to constrain the inner vent radius r and the depth z of their origin. (b) ‘Trajectory intersection approach’ (TIA): by measuring the exit angles γ and δ of two straight trajectories within an individual pulse and their horizontal distance s at the exit of the vent, it is possible to determine the depth of the intersection point z. A comparison between the different pulses reveals possible vertical (∆z) and horizontal variations (∆x) of the intersection points. (c) In contrast to traditional ballistic trajectory approaches, both methods presented use only straight trajectories, i.e., flight paths of high-speed particles (indicated in blue). Bent trajectories (marked in red) are neglected.