English: A striking example of a gully head erosion in Casa Branca, São Paulo State, Brazil. On the left we see the view from below and on the right it is the view from the top. We can see the three levels of step-like slips and yet the trees are still upright. Even the dense forest isn't enough to restrain the phenomenon. In spite of the presence of the vegetation the tunnelling erosion continues. The presence of lenticular mudstone beds in the local sandstone forces the underground water to flow horizontally, thus increasing the erosion rate.