Erosion Path (down hill into the valleys below) Image 2 of 2
This image was taken during a geology field study course I took. Even our professor was surprised at the amount of damage that we witnessed here and mentioned that there were a number of camping sites wiped out further below.
As for the cause we concluded it was started by a glacial outburst flood (also called by the Icelandic term "jokulhlaup") due to heavy rains and snow/ice melt in the early part of the year. An accumulation of water builds up behind an ice wall (such as as at base of a glacier) and eventually the force of the water causes the wall to yield and the water burst through it. The water rushing out erodes the surrounding surfaces and picks up sediment and debris along the way. The image shows mostly volcanic rock deposition which indicates this area was close to the source of the flow and just below the tree-line, otherwise mud and vegetation evidence would also be visible.