Top row: continuum images of three different exploding granules during the formation of the dark core recorded with the IBIS instrument. Second row: image in the background again shows the continuum image. Areas with a wavelet power for normalised line-core intensity oscillations in the Ca II 8542 Å (first two exploding granules) and Na I 5896 Å (last granule) lines are marked by contours, with the averaged power in the period range of 120 s to 190 s. Colours correspond to different percentages of the maximum power in the field of view (cyan 20%, blue 30%, green 40%, red 50%, yellow 60%, white 80%, and fuchsia 100%). Lower row: line-of-sight velocity oscillation power in the same format as the second row.