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Period of low-level seismic activity
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A number of very small earthquakes are recorded, but are not recognized as immediate precursors to possible volcanic activity.
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Magnitute 4.1 Earthquake
A magnitude 4.1 earthquake, unlike any that had been previously detected in the area, occurred just northwest of the summit of Mount St. Helens. Seismologists were uncertain as to whether or not these first earthquakes were related to volcanic activity. They decided to deploy additional seismometers in order to better monitor future activity. -
Earthquakes and steam-driven explosions occur off and on during this period.
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Earthquakes and steam-driven explosions occur off and on during this period.
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State officials asked the governor to close a large area around the volcano.
The plan called for a Red Zone (no public access) and a Blue Zone (restricted access). Emergency services officials are frustrated because the public appeared to remain unaware of the danger. -
Small explosions of steam and ash are emitted from the volcano.
Intermittent earthquakes up to magnitude 4.9. -
Law enforcement officials escorted about 50 carloads of property owners into the Red Zone to retrieve possessions.
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Mount St. Helens Erupts!
Video of Eruption Mount St. Helens erupted at 8:32 a.m. PST on May 18, 1980, reminding Pacific Northwest residents and people around the world of the powerful and uncontrollable forces of nature. Physical effects of the eruption were experienced in dozens of U.S. states, with ash falling as far away as Oklahoma. -
Period: to
Small Eruptions Continue to Occur Overtime
