Mount St. Helens Eruption Timeline

By ljudson
  • March 15-19

    A number of very small earthquakes are recorded, but are not recognized as immediate precursors to possible volcanic activity.
  • March 20

    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.
  • March 27 to April 18

    Earthquakes and steam-driven explosions occur off and on during this period.
  • April 29

    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 da
  • May 7-13

    Small explosions of steam and ash are emitted from the volcano. Intermittent earthquakes up to magnitude 4.9.
  • May 17

    Law enforcement officials escorted about 50 carloads of property owners into the Red Zone to retrieve possessions.
  • May 18

    Here is the sequence of events that occurred during the May 18 eruption of Mount St. Helens: