Rest in peace, David Johnston. About.com article quote:
The Mount St. Helens Legacy
The research continued. The methods first tested at Mount St. Helens were deployed and advanced in later years and later eruptions at El Chichón in 1982, at Mount Spurr and at Kilauea, and more volcanologists died: on Unzen in 1991, on Galeras in 1993.
In 1991 the dream came to fruition spectacularly at one of the century's largest eruptions, at Pinatubo in the Philippines. There the authorities evacuated the mountain and prevented thousands of deaths. The Johnston Observatory has a good story on the events that led to this triumph, and the program that made it possible. Science served civic authority again at Rabaul in the South Pacific and Ruapehu in New Zealand. David Johnston's death was not in vain.
National Geographic ran a beautiful set of photos regarding the regrowth of the mountain habitat and the new dome.
USGS site of Mount St. Helen references