On each of the mountains studied substantial amounts of snow and ice exist within probable eruptive zones and should be considered as factors in all eruption-hazard analyses. In times of eruption their role as hazards will depend on the extent of seasonal snow cover and eruption characteristics.
Glacier sizes and locations vary greatly on the volcanoes, depending on the local climate and each mountain's topographic configurations. Mount Rainier, the highest and farthest north of the volcanoes, has by far the largest and most well developed valley glaciers and snow patches. The Three Sisters and Mount Shasta have only one major valley glacier eachCollier and Whitney Glaciers, respectively. Mount Rainier's size is reflected in its large snow and ice volume (156.2 billion ft3), when compared to those of Mount Hood (12.3 billion ft3), Mount Shasta (4.7 billion ft3), and the Three Sisters (5.6 billion ft3).
The methods of volume estimation used in this study were developed by using relations derived from the ice-radar measurements of glaciers. The methods have been tested on glaciers with known volume and found applicable and valuable for use on glaciers of Cascade volcanoes in Washington, Oregon, and northern California. However, because glacier area and shear stress relations may vary with climate, it is important that care be taken in determining the suitability of the methods to glaciers elsewhere. The choice of using an area or a basal shear stress correlation is as important as determining the geographical suitability of a glacier. Glaciers not well defined in length and continuity may require some forethought and preliminary estimations of volumes before final estimations are made.
Last Updated: 28-Mar-2006