Digital Shasta — Applying GIS Technology to Volcano Hazards

The U.S. Geological Survey(USGS) Volcano Hazards at Mount Shasta project is charged with mapping the geology and assessing the volcano hazards of the Mount Shasta region. Mount Shasta was chosen for study because it is the largest Cascade Range stratocone volcano and has produced more documented eruptions in the past 4,000 years than any Cascades' volcano other than Mount St. Helens.

Basement Surface Inside Mount Shasta

At 14,161 feet, Mount Shasta is the highest and most recognizable landmark in northern California. Its snow and glacier covered summit dominates the skyline. It is also potentially the most dangerous volcano in northern California and one of the most dangerous in the Cascade Range, a chain of volcanoes that stretches from British Columbia to California. Future eruption activity from Mount Shasta could threaten people's lives and property and could hinder or cut off travel through the Shasta region, the major transportation corridor between California and the Pacific Northwest.

The geologic map consists of 1:24,000-scale mapping of the geology of nine USGS 7.5-minute quadrangles. The project is still in progress, and when completed the mapping will cover parts of 35 USGS 7.5-minute quadrangles. The geology was mapped in the field on USGS 7.5-minute quadrangles and compiled as a digital map database in ArcInfo. These field sheets were cut into four pieces each to help eliminate distortion. The pieces were individually scanned, transformed into ArcInfo grids, and georegistered. The grids served as the raster background over which the vector geologic coverages were digitized in ArcInfo.

This work resulted in a detailed database that can easily be compared to and combined with other geospatial data, such as U.S. Census Bureau population figures, slope calculations, and elevation data, to visualize and analyze volcano hazards and their potential effects at Mount Shasta.