After the frightful landfall of Cyclone Gita in Central New Zealand, torrential rains flooded the area causing floods and landslides. One such landslide transformed the “Terrible Gully” of the Rakaia River into a terrifyingly beautiful steady stream of flowing rocks. This phenomenon is known as granular flow or “quasi-liquid flow” as captured by local breeder Donna Field.
Often called a quasi liquid flow these rocks are travelling like a river from the mountains to be deposited in a fan shape where the land flattens out. We are having rain as the former Cyclone Gita hits New Zealand
via Stuff, BBC News, Landslide Blog