Remembering The 40th Anniversary Of The Mount St. Helens Eruption

In October of 1792, the crew of the H.M.S. Discovery was surveying the west coast when they spotted a cone-shaped mountain. The ship's captain named it after the British diplomat Alleyne FitzHerbert, 1st Baron St. Helens. However, the true nature of Mount St. Helens was discovered by scientists only in 1835 when a minor eruption revealed its volcanic origin. In November 1842, the missionary Josiah Parrish experienced a rain of ash, probably coming from St. Helens. This phase of volcanic activity continued until 1857. Minor eruptions happened in 1898, 1903 and 1921. Oral traditions suggest that Mount St. Helens was already active long before the first written records.

To the Klickitat people, the mountain was known as Louwala-Clough, the One From Whom Smoke Comes, or as Tah-one-lat-clah, The Smoking-Mountain. The names derive likely from the direct observation of past eruptions. In 1800, the Sanpoil and Spokan nations told to the first missionaries and traders visiting the area of an eruption occurring at St. Helens: "The people called it snow… The ashes fell several inches deep all along the Columbia and far on both sides. Everybody was so badly scared that the whole summer was spent in praying. The people even danced – something they never did except in winter."

In 1969, geologist Dwight Crandell warned in a conference in San Francisco, that the volcanoes of the U.S. were still poorly studied and monitored and much more active than previously assumed. Based on dated deposits of past explosive eruptions, Crandell and his colleague Donal Mullineaux published a paper, in which they warned that, "the scheme of activity of St. Helens led to the assumption that it is possible to postulate an eruption in the next 100 years and maybe even before the end of this century."

In March 1980, a monitoring system was installed on St. Helens. From the very beginning, the system registered increased seismic activity with magnitude 4 earthquakes happening periodically, accompanied by steam explosion in the crater. In April the northern slope started to inflate, a phenomenon caused by intruding magma inside the mountain. An eruption seemed inevitable and the area around the volcano was closed to the public.

At 8:32 a.m. on May 18, an earthquake of magnitude 5.1 triggered a landslide on the northern slope of the mountain, followed by a gigantic explosion. In just 60 seconds, a series of 1,100°F hot pyroclastic flow burned 1,500 square miles of forest. Mud flows caused by melting ice and the overspill of Spirit Lake devastated the Toutle River valley. Despite the previous evacuation, 57 people were killed by the eruption, many of them scientists studying the volcano. David Johnston, a U.S.G.S. geologist, was well aware of the possible risk of staying with his observation station close to the mountain, but he remained there right up to the moment of the eruption. His last recorded words were the first mention of the eruption: "Vancouver, Vancouver, this is it!"

Thanks to the many scientists and volcano enthusiasts gathering around the volcano and a high degree of media interest at the time, the eruption of St. Helens is one of the best documented in history.