PARADISE RIDGE, Mount Rainier — They were a scientific odd couple, a perfect pair to make a breakthrough discovery. Geologist Dave Lescinsky knew glaciers, and his sure-footed mountain-climbing friend Tom Sisson had seen more of Rainier's oddities than most scientists. For years, it was assumed Mount Rainier's 25 mightiest glaciers chewed Washington's tallest volcano into its irresistibly craggy form. As lava spewed from Rainier's gullet over the eons, the theory went, fiery molten rock gushed from the summit, filling the valleys. Then the rivers went to work, sluicing out new valleys, ultimately exposing Rainier's signature ridgelines. Lescinsky and Sisson weren't...