The recent eruptions of Mount St. Helens are the first volcanic eruptions in the continental United States since California's Mount Lassen in 1917. Geologists were not surprised when St. Helens ended its 123 year dormancy. Mount St. Helens is still in the cone building stage. During the past 600 years Mount St. Helens has erupted every 100 to 200 years. As a matter of fact, it has been the most active and violent Cascade volcano for the past 4500 years.
Is Mount Rainier as active as Mount St. Helens? The answer is no. The last major eruption of Mount Rainier took place about 500 to 600 years ago, at which time there were heavy ash and pumice falls.
Unlike Mount St. Helens, which is younger and is materials, Mount Rainier is a composite volcano, andesite lava flows bedded between layers of ash composed of explosive pyroclastic built mainly of hundreds of andesite lava flows bedded between layers of ash and pumice.
It is believed that there was some volcanic activity on Mount Rainier in the 19th Century. The October 25, 1873 issue of the Washington Standard reported the following:
This was one of many newspaper accounts reporting eruptions on Mount Rainier on at least 14 different occasions between 1820 and 1894. Since geologists discovered only a light layer of ash from that time most of the "eruptions" which people reported seeing were probably only dust clouds rising from large rockfalls or the cloud cap frequently seen over Mount Rainier.
Will Mount Rainier erupt again? It is quite possible and scientists are monitoring it carefully. Yet, no one knows for sure when, and if, it will wake up from its dormancy. Hopefully, the complex mysteries of volcanoes will diminish as geologists gain more insight through their study of Mount St. Helens.
Mazama Ridge: Mazama is a Spanish word for "mountain goat" and is the name of the climbing club of Portland, Oregon. The club had many outings on Mount Rainier beginning in 1905. The ridge is below the Paradise Glacier east of Paradise Lodge in Mount Rainier National Park. The Mazama climbing club was organized on the summit of Mount Hood on July 19, 1894. It was the second climbing club to be organized on the Pacific Rim, the first being the Sierra Club which was founded by John Muir in 1892.
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