POST-ERUPTION MAPPING AT MOUNT ST. HELENS

Elizabeth Colvard

The astonishing displacement of one cubic mile of earth, blown asunder in the violent eruption of Mount St. Helens on May 18, 1980, created an urgent need for mapping support from the USGS. The Western Mapping Center responded with professional, enthusiastic support, answering the emergency with an expeditious publication of multiple mapping products. The immediate objectives included the development of a 1:100,000-scale topographic regional map (pre-event version), nine vicinity 1:24,000-scale orthophotoquads, and a reduced-scale mosaic of the nine orthophotoquads. A variety of other post-event products were also planned.

The bulk of responsibility for the development of the 100K vicinity map went to the Cartography group. In a flurry of activity, available materials were assembled and evaluated. The original Mount St. Helens 100K quad had been produced as a planimetric version by the Bureau of Land Management (BLM), necessitating the generation of an engraved contour plate. Six employees, working on a 24-hour three-shift basis, accomplished the trying task in just three days. Further, the most recent road update had to be incorporated into the final composite. The cumulative responses of the edit, compilation, photo lab, and digital sections provided the final press-ready plates within an extraordinary eight working days.

In the Photogrammetry group, the orthophotoquad demands were met with equal promptness. Within a single day, composite negatives of the nine vicinity orthophotoquads were prepared and forwarded to Reston for a congressional briefing. In addition, the photo lab produced the nine-quad mosaic at a scale of 1:50,000.

Back to index