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Facts about Mount St. Helens

21 Mount St. Helens facts

America's deadliest volcano

Mount St. Helens is a stratovolcano located in North America. It is a part of the Pacific Ring of Fire, and the Cascade Volcanic Arc. It is associated with one of the largest eruptions that occurred in the 20th century.

1
Mount St. Helens is an active stratovolcano in Skamania County, Washington.

A stratovolcano is a steep-sided volcano, which cone is made up of lava, ash, and debris. Their explosive eruptions cause avalanches and landslides.

2
It is a part of the Cascade Volcanic Arc.

It is a number of volcanoes in North America, extending for 1,100 kilometers from southwestern British Columbia up to Northern California.

3
It was named after a British diplomat, Alleyne FitzHerbert, 1st Baron St. Helens.

He was a friend of British captain George Vancouver, who explored the northwestern parts of the Pacific Coast of North America, and spotted Mount St. Helens on May 19th, 1792.

4
It is located 80 kilometers south of the highest volcano of the Cascade Arc, Mount Rainier.

5
It dates back to the Pleistocene 40,000 years ago.

It is relatively young for a volcano.

6
According to the U.S. Geological Survey, most of the volcano cone is relatively young and was formed over the last 2,200 years.

7
Mount St. Helen is the youngest and the most active volcano of the Cascade Arc.

8
On March 1st, 1980, a new seismographic system was installed by the University of Washington in order to monitor seismic activity in the Cascade Arc.

The area of Mount St. Helens experienced an increase in earthquakes, and the first major, of a 4,2 magnitude, occurred on March 20th. It was the first indication of imminent volcanic activity.

9
Three days after the first major earthquake, another one occurred.

It was a 4.0-magnitude earthquake followed by a series of smaller earthquakes, which continued to intensify until March 23rd.

10
On March 27th, the volcano released a 1,829 high steam and blasted a crater 75 meters wide.

11
Until April 22nd, Mount St. Helens was erupting daily, with a frequency of one per hour to one per day.

12
The volcano resumed its activity on May 7th, and the rate of eruptions was gradually increasing until May 17th.

13
The deadliest and economically most destructive eruption occurred on May 18th, 1980.

It took the lives of 57 people and destroyed homes, bridges, roads, and railroads. The eruption lowered the mountain’s summit to 2,549 meters (from the previous 2,950 meters). The blast was triggered by a 5,1-magnitude earthquake followed by a debris avalanche. Within minutes, an area of 595 square kilometers was destroyed. The rising level of river waters caused flooding in the surrounding valleys.

14
The 1980 disaster was the first major eruption since 1800.

15
Several minor eruptions occurred throughout the 19th century, the last dated 1857.

This period is known as the Goat Rock Eruptive Period.

16
In the aftermath of an eruption, the ecosystem of the area surrounding Mount St. Helens changed drastically.

Only aquatic life thrived as a result, thanks to volcanic ashes falling into the water.

17
A previous major eruption, several times more powerful than the one from 1980, occurred some 3,600 years ago.

18
In 1982, the area surrounding the volcano was declared as a National Volcanic Monument.

It is administered by the National Forest Service.

19
Mount St. Helens was continuously active until 2008.

Currently, geologists claim the seismic activity around the volcano is within a normal range.

20
Geologists claim there are more eruptions to come.

Their magnitude may be more destructive than that of 1980.