Geologic Publications for Mount Rainier
Glacial changes between 1985-2009 and implications for volcanic hazards at Mt. Rainier, Washington
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Jon E. Sanford
Oklahoma State University
Glaciers throughout the world have shown decreases in size in recent years (WGMS, 2008). Because of their sensitivity to temperature and precipitation changes, glaciers are good indicators for climate change (Nylen, 2001). Glaciers located in temperate areas are especially sensitive to warming due to their relatively quick flow and high mass turnover (WGMS, 2008). In areas with significant amounts of glaciation, a warmer climate can have a considerable effect.
A ~0.6°C increase in the mean global temperature is responsible for the overall retreat of mountain glaciers since the early 20th century (Hock et al., 2005). Further decreases are expected due to increased global warming as predicted by General Circulation Models (Hock et al., 2005). Several potentially active volcanoes with rapidly thinning glaciers are located in Mexico, Columbia, Chile, and Tanzania (Tuffen, 2010). Tuffen (2010) estimates that if the current rate of thinning continues glaciated volcanoes would lose a large portion of ice. At Popocatépetl in Mexico, this has already happened. The amount of ice on Popocatépetl decreased 53% from 1996-2001, which was partially due to eruptive activity (Julio-Miranda et al., 2008). Other mountain glaciers around the world have also experienced decreases in areal extent. The World Glacier Monitoring Service (WGMS) reports that annual melting rates of mountain glaciers have doubled since the turn of the century (WGMS, 2008). New records for ice loss were also set in 2003, 2004, and 2006 (WGMS, 2008). Significant glacier changes could affect local hazards due to the decrease in glacial coverage and the increase in melt water. Glaciers, ice caps, and ice sheets cover approximately 10% of Earth‟s surface and contain 75% of its freshwater (UNEP, 1992; Nylen, 2001). Hazards in volcanic regions that could occur as a result of melting glaciers include lahars, debris/ice avalanches, eruptions, and jökulhlaups (glacier outburst floods) (Hoblitt et al., 1998). Recent changes in glacial extent on Mt. Rainier could increase hazard risks due to the increase in melt water and steep exposed slopes (Crandell, 1971). The large amounts of loose debris, along with slopes that have been weakened as a result of hydrothermal alteration, also increase hazard risks at Mt. Rainier (Reid et al., 2001). The amount and rate at which Mt. Rainier glaciers are retreating is important for determining risks from hazards such as lahars, debris avalanches, eruptions, and jökulhlaups.
Remote sensing provides an alternative method of monitoring glaciers changes as opposed to ground surveys or aerial photographic surveys. Glacier mapping using satellite images is generally less expensive and involves a smaller amount of labor than ground and aerial surveys (Sidjak and Wheate, 1999). Many studies have used Landsat images to map and interpret glacier changes around the world in places such as Iceland, British Columbia, Austria, and Peru (Williams et al., 1997; Sidjak and Wheate, 1999; Paul, 2002; Silverio and Jaquet, 2005). They show that satellite images are useful for collecting data on glacier extent, which can then be used for water management and climate monitoring purposes (Sidjak and Wheate, 1999). They are especially useful in places like the Tibetan Plateau, where areas with rugged terrain and lack of access make ground surveys very difficult or impossible (Zhen et al., 1998).
This study concentrates on the changes in glacier areal extent that have occurred at Mt. Rainier and some of the possible consequences of those changes in terms of volcanic hazards. The first objective of this study is to measure the changes in glacier area from 1985-2009 at Mt. Rainier with satellite images. This study maps the areal extents of glaciers and groups of glaciers on Mt. Rainier as a function of time and then examines the rate of ice loss or gain for each glacier/glacier group as well as the rate of total ice loss or gain. These measurements are compared with measurements made by the United States Geological Survey (USGS) and the Global Land Ice Measurements from Space (GLIMS) project. The second objective is to determine the possibility of an increased risk for eruptions at Mt. Rainier due to the removal of glaciers from its slopes. This study examines the relationship between glacier change and eruption rates in the past by comparing the modeled glacier area at Mt. Rainier for the last 10 ka to the eruptive history of Mt. Rainier and other Cascade volcanoes during the same period. Any correlations between times of deglaciation and increases in eruption rates could help in predicting future volcanic activity resulting from continued glacial retreat at Mt. Rainier.
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In Text Citation:
Sanford (2011) or (Sanford, 2011)
Sanford, J.E., 2011, Glacial changes between 1985-2009 and implications for volcanic hazards at Mt. Rainier, Washington: M.S. Thesis, Oklahoma State University, 67 p..