by Jane Koerner My turn to tie into the umbilical cord, the dangling rope. I start around the corner, and the route to the top of Dallas Peak disappears into thin air, like Will did 45 minutes ago when he took the lead. Once my eyes adjust to the glare, I realize I am standing on a snowed-in ledge that leans away from the mountain, toward Blue Lake 2,000 feet below. My postholes in the snow cannot take the heat at this altitude, and the only secure route back to terra firma, and to John, who is awaiting his turn,…