May 18, 2010 -- On a sunny Sunday morning thirty years ago today, Mount St. Helens exploded in one of the most powerful volcanic eruptions of the 20th century. For two months prior, geologists had watched as earthquakes swarmed under the mountain, and its north flank swelled by up to five feet a day. Onlookers gathered around the mountain, hoping for an awesome display of tectonic power. Among them was David Anderson of Portland, Oregon.
The afternoon before the blast, Anderson snapped the above picture, in which the trembling bulge on St. Helens' north flank is easily visible. Luckily, he spent the day of the eruption with a friend on the Pacific coast. "If I hadn't been at the beach, I would have been a lot closer than I would have wanted to be," he told Discovery News.