Early on the morning of May 18, 1980, Arlene Edwards, a freelance photographer from Portland, Ore., and her 19-year-old daughter, Jolene, drove across the Columbia River to a high outcropping of rock in southwestern Washington State. There they set up Arlene's camera and began to watch the Mount St. Helens volcano 10 miles to their southeast. For the previous two months the volcano had been spitting out ash and steam, and the Edwardses were among dozens of observers on surrounding ridges who thought they were a safe distance away. It was a gorgeous Sunday morning, the air warm and still beneath a cloudless sky, the volcano grand and terrible under its ash-streaked glaciers.