Mount Rainier, Washington, Is One

Mount Rainier, Washington, is one of the few active volcanoes in the continental United States. It is classified as a stratovolcano, or composite volcano, meaning that it is a tall, more conical volcano built up over the years with numerous layers of strata that includes hardened lava, pumice, and volcanic ash. Unlike shield volcanoes, the more typical look shown in movies and nature films, stratovolcanoes have a steep profile and periodic, but extremely explosive, eruptions (Watson).

The Mountain itself is one of the more distinctive features of the State of Washington. It is also the most prominent mountain in the continental United States at 14,411 feet, and is the highest mountain in Washington and the entire Cascade Range (Signani). It is located just 54 miles southeast of Seattle, and is part of a protected area, the Mount Rainier National Park. This area has 26 major glaciers, 36 square miles of permanent snowfields, and is the most heavily glaciated peak in the continental United States. The summit itself is topped by dual volcanic craters, each over 1,000 feet in diameter. These craters are free from snow and ice due to continued exposure to geothermal heat. This melt water formed the world's largest network of glacier caves and the highest crater lake in North America (Zimbelman, Rye and Landis).

Mount Rainier's topographic prominence (13,211 feet) is greater than that of the Himalayan K2, ranking 21st globally. On clear days the image of Rainier dominants the entire southeastern horizon for most of the Greater Puget Sound area. In fact, on many days, due to exceptional clarity and prevailing winds, it can be seen as far away as Portland, Oregon and Victoria, British Columbia (World Top 50 Mountains By Prominance).

Stratovolcanoes -- Stratovolcanoes are typical in subduction climactic zones, and often form along plate tectonic boundaries where ocean crust seeps underneath continental crust. Some examples of this are, of course, the Cascade Range, the Central Andes Mountains, the Aleutian Islands, and the Mount Fuji area of Japan. While some of the most picturesque volcanoes, they are also the most deadly. This is often due to not only their proximity to population centers (Seattle, Tokyo), but the way the layers of material that are deposited on the outside of the volcano, making the lava flow downward fast and with very little geologic or flora to slow the flow. Additionally, the more gentle lower slopes, steep upper slopes, concave shape and small summit crater tends to concentrate the potential energy of the eruption (Stratovolcanoes).

Additionally, stratovolcanoes are dangerous because of their highly explosive eruptions, associated with hot volcanic fragments, toxic gases that flow down the slopes at hurricane force speeds, and a tremendous potential for lava flow. Stratovolcanoes erupt infrequently, and typically have a waiting period of several hundred years between eruptions, which also makes their potential energy that much greater (Wood and Kienle, eds., 155-9).

Geology of Mount Rainier -- Mount Rainier may be as old as 900,000 -- 1,000,000 years. Some of its earliest lava flows are 840,000 years old and the present cone is dated at around 500,000 years. Rainier is highly eroded, with several older glaciers on its slopes. The mountain is made mostly of andesite, an extrusive igneous-based rock somewhere between basalt and dacite in composition. Rainier was likely much taller about 5,000 years ago, or closer to 16,000 feet. Due to the amount of glaciation and shape, the area produced huge volcanic mudflows, known as lahars (U.S. Geodynamics Committee and the National Research Council).

Glaciation on Mount Rainier -- Glaciers are an important feature of Mount Rainier, not only for the mass and dynamic structures, but because they are a vital source of water for several rivers that supply hydroelectric power and irrigation. At certain times of the year, the flow rates of these glaciers are dramatic; the Nisqually was measures as fast as almost a yard per day during summer and the congruent met water (Zimbelman, Rye and Landis). On Rainer, as in most other glaciated areas, micro-climate conditions regulate the size and shape of glacier activity -- largely due to the control of snowfall and melt. Most of Rainier's glaciers advanced fairly regularly post-World War II and into the early 1980s, likely as a response to relatively cooler temperatures. Since the early 1980s, whether from global warming or simply a natural pattern, most of Rainier's glaciers are thinning and retreating. "The position of the snout, or terminus, of a glacier may change as the relative quantities of snowfall and glacier melt change. If summer melt exceeds winter snowfall, the terminus retreats, whereas if snowfall exceeds summer melt, the terminus advances. These changes in terminus position do not occur instantaneously, but typically take several years or more to become apparent. Glaciers are therefore sensitive indicators of climate changes" (Driedger).

Human Interaction With Mount Rainier - Mount Rainier is a cultural icon to contemporary Washingtonians and the spiritual icon for many of the Amerindian populations of the Pacific Northwest. One partial reason for this is the location; it towers above a relative flat plain just southeast of Seattle and is visible most of the year as a towering symbol of both nature's beauty and the omniscient potential of eruption. This is especially true due to its proximity to Washington's other volcano, Mount Saint Helens, and the cultural memory of its eruption on May 17, 1980 -- the deadliest and most economically destructive volcanic event in the history of the United States (Service). Most of Rainier's glaciers advanced fairly regularly post-World War II and into the early 1980s, likely as a response to relatively cooler temperatures. Since the early 1980s, whether from global warming or simply a natural pattern, most of Rainier's glaciers are thinning and retreating (Driedger).

Mount Rainier was first known by Pacific NW Native Tribes as Talol or Tacoma, meaning mother of waters. Captain George Vancouver reached Puget Sound in 1792 and was the first European to see Rainier, naming it after his friend, Read Admiral Peter Rainier (Historical Notes - Vancouver's Voyage). The famous naturalist John Muir climbed Rainer in 1888 and became a strong advocate of protecting the mountain. In 1893 it was set aside as part of the Pacific Forest Reserve in order to protect its two most viable resources, water and timber. In March of 1899, the area became Mount Rainier National Park, America's fifth (Duncan and Burns).

Modern Activity and Current Threat Ratio- Most scholars consider Mount Rainier to be both the largest and most dangerous volcano in the United States (Goebel). The most recent recorded eruption was been 1820 and 1854, not very accurately documented. It is considered an active volcano, though, and in 1998 the United States Geological Survey put together a formal plan, the Mount Rainier Volcano Lahar Warning System and Emergency Evacuation Plan. It is not just from the eruption of Rainier, though, that many scholars note is the largest danger. Instead, the view is that a giant wave of mud and debris would flow down the mountain and bury cities all the way to Seattle, flowing in the Puget Sound (Parchman). The threat, though, is neither considered imminent nor of great alarm. However, Mount Saint Helens was not considered dangerous either and both climatologists and geologists concur that Rainier is long overdue for a major eruption sometime in the 21st century (Drieger and Scott).