This is a drone image directly above the summit of An Groban, showing the pattern of channels which was probably blasted out by a lightning strike !

It seems strange that the strike hit the ground about 2 metres away from the highest point (the trig point). There is no charring, but the contact point is a mass of shattered rock, and channels in the soil radiate out in all directions from it, sometimes disappearing through solid rock and reappearing again on the other side. You may be able to see in the image that the channel runs underneath a large boulder and continues beyond it.

awildplace