This is a photomontage of the gorge prior to the mudslide.  The yellow lines represent the level at which the glacier,
mud, and debris was piled.  This was originally published in the New York Times Magazine.  I would have linked to their site,
but they never put this feature up on the site.
It is estimated that the piece of the glacier that broke off  weighed approximately 8 million tons.  By the time the
slide came to rest, 20 million tons of mud and ice filled the valley..