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Period: 275 BCE to 35 BCE
Ape Canyon Stage
In this stage, several lava domes erupted. The elevations were very high: about 1200 to 4000 feet. -
Period: 28 BCE to 18 BCE
Cougar Stage
In this stage, large volumes of ash, lava domes, debris avalanches/lahars, and mudslides, are included in this stage. This was a very dangerous and eruptive part of the process. -
Period: 16 BCE to 12 BCE
Swift Creek Stage
This stage included more lava domes, and materials. This was a shorter stage. There were 2 phases. The first phase consisted of pyroclastic flows, lahars, and 3 extensive fans from the collapsing/failing lava domes. The second phase had an explosive eruption with no pyroclastic flows or lava domes were included in this activity. This is a good thing. -
Period: 3 BCE to
Spirit Stage
In this stage, there were several periods of eruption. Some of them lasting for thousands of years. Most of these eruptions contained tephra, pyroclastic flows, and lava domes. -
The First Sign of Activity since 1857
There were small earthquakes that showed the first signs of activity -
Period: to
Eruption Period
This period was hundreds of small earthquakes showing small signs of activity. Then, on March 27, there were a huge series of eruptions. In March, there were about 1 an hour, and in April, there was about one a day. THis lasted all throughout May. -
The Biggest Debris Avalanche in History from Mount. St. Helens Accompanied by a series of rapid events.
Here, it started with a 5.1 magnitude earthquake, and this caused the volcano's northern bulge to slide down and create a landslide. This landslide was the size of 1 million olympic swimming pools. -
Eruption of Mount St. Helens
The cryptodome was uncovered from inside the volcano and it caused a huge lateral blast with the ash traveling approximately 5333 feet per minute. Pic of devastation -
Plinian Eruption
This eruption also happened on May 18, 1980 at around noon. At this point, pressure was released from the volcano and caused an eruption that made ash flood the skies of Washington, and Montana. This made it hard to breathe, and pitch black; they couldn't see anything. -
Period: to
Small Eruptions
In this time period, much smaller eruptions happened from late May to October. These eruptions often consisted of ash and pumice and came out of the lava domes.
