Mount St. Helens had been labeled in a 1975 U.S.Geological Survey report as the Cascade volcano most likely to erupt. When frequent earthquakes began beneath the mountain on March 20, 1980, the potential for volcanic activity was recognized quickly by University of Washington seismologists and soon was accepted by most other knowledgeable scientists. Officials of emergency-services agencies and other appropriate organizations at all governmental levels were alerted to the possibility of an imminent eruption. Scientists quickly stepped up the collection and interpretation of pertinent geologic, geophysical, hydrologic, and atmospheric data. As events progressed toward the climactic eruption of May 18, scientists, law-enforcement officers, and other responsible officials teaed up in round-the-clock efforts to evaluate the increasing hazards and to protect tourists and local residents (often against their will) while also attempting to minimize panic and hardships among the citizenry. Officials of the State of Washington and the U.S. Forest Service established restricted-entry zones around the volcano. Most people respected these restrictions, but the spectacular eruptions of steam and ash from the mountaintop were an irresistible attraction to some, who entered the danger zone by way of logging roads too numerous to blockade. An information center established at Vancouver, Washington, coordinated the release of warnings and other information, including thousands of news releases and responses to telephone inquiries, daily briefings by scientists, and explanatory meetings with officials and local citizens.
From mid-April to May 17, eruptions and seismic activity diminished to such a degree that some residents and loggers were clamoring for entry into the restricted area near the volcano. (Limited entry was, in fact, granted on May 17 and scheduled also for the morning of the cataclysmic eruption.) The scientific data, however, showed that the mountain was bulging on its upper northern side and undergoing other ominous changes and, therefore, that the hazards were increasing rather than decreasing. Although opposition to official restrictions was widespread before the May 18 eruption, the human responses to the far-reaching effects of that eruption included acts of exceptional heroism, and selfless cooperation was commonplace.
The May 18 eruption differed from what was generally expected by the scientific team mainly in the character and destructiveness of the lateral blast and the lack of prior seismic warning. With these notable exceptions, the scientists' evaluation provided an ample hazard warning and unquestionably saved hundreds of lives. That evaluation was based not only on the many-faceted project for monitoring restless Mount St. Helens but also on information obtained by earlier geologic investigations of this volcano, of other Cascade volcanoes, and of other volcanoes of the world.
Hazards that continued after the first 100 days of activity at Mount St. Helens in 1980 included possible ashfall and ash clouds, pyroclastic flows, lateral blasts, lava flows, floods, mudflows, and fires. The main flood hazard existed along the channels of the Toutle and lower Cowlitz Rivers, which were so choked with mudflow deposits from the May 18 eruption that normal wet-season runoff could have caused severe overbank flooding. Dredging undertaken on an emergency basis to open the channels probably will be continued in subsequent years.
The volcanic activity at Mount St. Helens during the 100-day period ending June 27, 1980, is not exceptional in recorded history or in the evolution of the Cascade Range. Mount St. Helens was only one of perhaps 50 volcanoes worldwide that were active during 1980, although its May 18 eruption was by far the most powerful during the year and, perhaps, during the last decade. At the end of the 100-day period, the mountain remained dangerous to those nearby, but the near-term likelihood of another eruption as destructive as that of May 18 was considered to be small. So far as is known, the 1980 eruptions of Mount St. Helens do not increase the probability that other Cascade Range volcanoes will erupt. The eruptions should, however, serve as a reminder that other Cascade volcanoes will erupt in the future as surely as they have in the past and that they are likely to produce effects that no amount of farsightedness or good intentions will be able to prevent.
The outlook for the future of Mount St. Helens and the areas that it affected can be discerned only partially. Salvage of blown-down timber was begun in June 1980, but proposals have been made to incorporate part of the devastated forest area into a park. Tourists are expected to be attracted in great numbers. Future uses of land near the volcano probably will resume largely as they were -- forestry, farming, recreation, and hydropower generation -- but will depend ultimately on the behavior of the volcano. The volcano might go through a period of dome building (as it was on June 27, 1980) interspersed with occasional explosive eruptions; it might extrude enough lava to overflow the crater that was left open to the north; or the volcanic activity might simply stop indefinitely at any stage.
In the meantime, the ash gradually will be assimilated into the soil. The streams and lakes that persist on the mountain flanks and in the devastated area will adjust to the new conditions of runoff and sediment load. Glaciers and snowfields will adapt to the different shape and lower altitude of the cone. Animals and vegetation, already returning to the devastated areas at the end of June 1980, will become abundant again. The restorative phase of the cycle, repeated many times before at this volcano and others in the Cascades, has begun once more.
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