A small rockslide came down on a portion of westbound Interstate 90 about 13 miles west of Easton on Sunday afternoon.
The State Patrol said the slide occurred at about 4 p.m. just east of the snow shed.
The Department of Transportation said there was an eight-mile backup by 5:30 p.m.
A huge boulder landed in the right lane with debris in the left lane.
Traffic was getting by in the left lane and on the left shoulder.
The right lane is closed until further notice.