Gnarly Ground

Gnarly ground is formed when the intrinsic magic in the ground is pushed and squeezed together by geological action. It causes the landscape to contain more than the eye can see, literally, a piece of marsh that would normally be crossed in 20 minutes may take hours to cross, a stream that appears to be a mere trickle may become a gushing, tumbling wild mountain river. As Nanny Ogg explained (when she and Magrat went looking for Granny Weatherwax after her invitation to the christening of Magrats baby had been "stolen" by magpies see: Carpe Jugulum), ..the landscape is psycho-reactive, that is, the moor is full of flowers and the river a gentle stream - because she was in love. If you're in a bad mood, the marsh is an evil bog full of flies and the stream is a murderous torrent.