Officials in the US have found another piece of debris from the tsunami in Japan last year, a 20 m long, rusting dock that washed ashore near the city of Portland in the state of Oregon. The dock was originally one of four that were swept away by the tsunami, one has already been found near Misawa, but two more are still missing, perhaps afloat in the middle of the Pacific Ocean. Al Jazeera's Dominic Kane reports.