Velocities at different intensity levels in the spectral line at which the bisectors are calculated (corresponding to different atmospheric heights) for the centre of the dark core plotted over time. The upper plot shows the velocities of IBIS 2 granule, inferred from the 6173.0 Å line. The lower plot shows the velocities of IMAX 3 granule, inferred from the 5250.2 Å line. The left dashed line marks the time at which the dark core is visible for the first time, and the right dashed line marks the time at which the exploding granule is split into a new generation of granules.