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Mt. Rainier
Angelina McKee
Physical Geology
Spring 2006
                         Mt Rainier: An Active Volcano in Wait

Mt. Rainier/Tipsoo Lake


Nestled in some 235,625 acres of Washington state wilderness Mt Rainier, a dormant volcano lays in wait. Although Rainier is a picture of the majestic beauty possible on earth, its peaks reaching heavenward at 14,410 feet it has the potential to inflict disasters of biblical proportions. To onlookers the peak may seem relatively harmless, to the experienced backpacker, climber, or skier the dangers on an eruption are rarely thought of seriously. It is no wonder however as it is enveloped by 35 square miles of snow and ice while its base is cradled by vast expansions of old growth forest and meows begging the question “there’s a volcano in there?” The deceptively beautiful landscape gives Rainier the look like anything but a volcano. Mt. Rainier is the largest peak in the Cascade mountain Range and because of the immense population that has taken root near its base it is also the most potently disastrous. Outdoor enthusiasts are drawn to Rainier national park and give very little thought to the danger it presents as do the populace that have settled and grown so near its base, although the fact remains that Rainier is a ticking time bomb that will ignite within the next hundred years.

As you can see in the illustration above, the area around Mt. Rainier is highly populated and due to the nature of volcanoes that erupt so irregularly the devastation would be much grater than with volcanoes that “let off steam” such as the many volcanoes found in Hawaii. Many active volcanoes dot the Cascade Mountain Range such as Mt. Baker and Mt. Adams but these like Rainier erupt so infrequently that they are vastly more cataclysmic.

The first known eruption took place approximately a half a million years ago, erupting as recently as 1840s without much devastation. The more extreme eruptions are estimated to have taken place between 1,000 to 2,300 years ago. The heat from molten lava has melted the glaciers and ice causing debris flow that are the consistency of wet cement. The unsettled landscape is believed to have been formed of pre-historic debris from the volcano and what is presently south Seattle and east Tacoma are settled on those debris. This gives cause to believe that when an eruption does take place it will in fact have the potential to devastate those cities and surrounding areas.

This is a photograph of Rainier’s summit. The depression is the major sign of a volcano, however, with modern ideas of what a volcano looks like the ice and snow make it seam impossible that molten lava is bubbling under the surface. The Cascades are constantly being observed for changes and activity due to the potently volatile nature. The PNSN and specifically the cascades volcano observatory take care to monitor the volcanoes and earthquakes that may present a danger to the cities and towns. In conclusion an eruption will accrue it is just a matter of time.

            In addition to locating regional earthquakes, the Pacific Northwest Seismograph Network (PNSN), in cooperation with the Cascades Volcano Observatory, is also responsible for monitoring seismic activity at volcanoes in the Pacific Northwest. The PNSN currently operates seismometers on or near Mount Baker, Mount Rainier, Mount St. Helens, Mount Adams, Mount Hood, Three Sisters, and Crater Lake.

          "Seismicity at Mount Rainier currently is at background levels, with 1 well-located earthquake (quality BB or better) occurring in the month of May, with a magnitude of 0.8. In an average month, 1-5 well-located, high-frequency earthquakes are recorded. In addition, small swarms of 5-10 earthquakes over a 2-3-day time period occasionally occur. All of these earthquakes are shallow, with most locating near sea level (~4 km below the summit), and are interpreted by Moran (1997) to be occurring in response to stresses associated with the circulation of hot fluids beneath Mount Rainier. These fluids are thought to be the source for the hot springs and steam vents found at the summit and at various points within Mount Rainier National Park (e.g. Frank, 1995)."


Sources Cited