A barrage of rockfall startles me as I slowly plod upwards towards the North Rim of the Grand Canyon. Rocks rain down crashing through the trees landing in a pile at the base of a cliff where the trail turns a switchback. Parts of the North Kaibab Trail are littered with rocks and boulders and a sign posted earlier warned: “Look and listen for falling rocks…A trail crew is currently working on the slopes…there is a high potential for rockfall. Use caution when hiking in this zone.” Well, what does that mean? Use caution? What am I supposed to do when rocks come down? I didn’t bring my hard hat.