The Afternoon Creek rockslide near Newhalem, Washington

A series of mass wasting events occurred above a Washington, USA, highway in the Cascade Mountains in November and December 2003. The largest event was a rockslide involving approximately 750,000 m³ that occurred on November 9, 2003. The source zone for this event was located at the crest of a ridge. Most of the debris fell to the east of the sharp ridge and was deposited in the relatively shallow sloping Afternoon Creek without causing damage to the highway. Lesser amounts of debris fell to the west of the ridge, sliding 600 m down the steeper Falls Creek and impacting the road. There is an evidence of one or more historical rock avalanches at this location. Displacement of reference points, ground vibration, crack extension, and tilting are being monitored due to concerns that future slope failures or remobilization of debris might again damage or block the highway.