They’re easy to spot this time of year in the North Cascades: thin and healthy, fast-moving hiking machines in their running shoes, lightweight backpacks and a look in the eyes that says they have places to go. It’s the annual migration of thousands of northbound (北行的) thru-hikers (全程远足者) traveling the 2,650-mile Pacific Crest Trail (PCT, 太平洋屋脊步道) from the Mexico border to Canada.