Selected velocity ranges of W43-Main (source 13). The location and size of the figures match those of Fig. 15. a) Shell-like structure in the ¹³CO map integrated over the channels from 80 to 90 km s^-1. b) Northern and southern parts of the cloud are separated by an abyss. The black star marks the position of the embedded OB star cluster. The plot is integrated over channels between 94 and 98 km s^-1.