Mount Saint Helens By Martina

Type of Volcano Mt. St. Helens is a mountain located in Washington, USA. Mt. St. Helens is a mountain located in Washington, USA. It is an active Stratovolcano. A startovolcano, also called composite volcano, is a tall, conical volcano which has many layers. Those layers are made of hardened lava, ash and other volcanic components. Composite volcanoes form when volcanoes erupt with lava flows and explode by throwing out their molten material. They are found at plate boundaries.

History of Mt. St. Helens The volcano was named by a British explorer, in honor of his Britannic Ambassador which was called Baron St. Helens. Mt. St. Helens is a 40,000 year old volcano. More than 25,000 years ago the volcano was shaped differently. In fact the dome was smaller and had a different shape. The pretty big eruptions which happened 25,000 years ago, rearranged the shape of the dome with its hardened lava and ash. The biggest eruption of Mt. St. Helens was on May 18, Some eruptions before that are: T The one is 1831, which wasn’t very big. he one in 1842, which threw ashes very far. There was another eruption in 1857, which didn’t do any damage. After that, the volcano became dormant, and stayed like that until May 18, 1980.

May 18, 1980 The Big Eruption: May 18, 1980

The eruption in 1980 Mt. St. Helens is a very famous volcano because of its catastrophic eruption which took place on May 18, It was the worst volcanic disaster in recorded history of USA. The eruption started at 8:32 am and continued until 6:30 pm.

Eruption Sequence

Description/Measurements of the Eruption When Mount. St. Helens Erupted, lava didn’t come out of it, but only ash did. Before the explosion, the ice and the snow on the top of the mountain started melting. Within three weeks a bugle was created on the northern side of the volcano. Than, small earthquakes with the Richter magnitudes between 2.5 and 4.2, occurred. After the small earthquakes, little amounts of smoke and ash columns about 2,100m high started coming out of the crater of the volcano. From that, people understood that the volcano would erupt sometime soon. On May 18, at 8.32 am, an earthquake with a Richter magnitude of 5.2 (about 1 mile beneath the volcano) shakes Mt. St. Helens. The northern broadside of the volcano detached (Landslide). The landslide traveled km/h. The water of the Spirit Lake (a lake located close to the forest) was displaced with the landslide, and 10m high waves covered up houses and camps. The landslide caused an avalanche which covered an area of 62km2. It also caused many mud flows. At the same time an explosion made the crater of the volcano become bigger and also made big amount of ash come out of it. The ash moved 100km/h. 

About three hours and 30 minutes after the eruption, the ash of Mount St. Helens reached Moscow, and 16 hours after the eruption began, the ash reached central Colorado. Before the Eruption, Mount St, Helens was 2,950 m tall. When the northern broadside of the volcano detached, Mount. St. Helens became 401m shorter, which means that after the eruption the volcano was 2,549m tall.

Human Impact The eruption killed 57 people, including Harry R. Truman, who became famous because he decided not to evacuate before the eruption. If the eruption occurred one day later, when the loggers would be at work, the death toll would have been much higher. A film crew was dropped by an helicopter on May 23, 1980, to film the remains of the volcano. On May 25, 1980, there was another eruption, and luckily, the crew survived and was rescued two days later by National Guard (Kind of army) helicopters. In the eruption, large amounts of ash came speeding out of the crater along with deep earthquakes. $1.1 billion = the worth of the damage done by the Eruption

Environmental Effects Mt. St. Helens’ eruption in 1980 caused lots of forests and houses to burn. Even the trees, 32 km away were destroyed! About 7,000 important animals for the chain (Food chain: Animal eating one animal that is eaten by another animal) died. Also 40,000 salmons died because of the mudflows. The Spirit lake which was displaced by the landslide, was 12m underneath mud. The roads also had lots of damage. In fact, 321km of railways, roads and highways were destroyed.

Bibliographies Barrows, Calder. The Ecological Impact of a Volcano-Mt. St. Helens. History of Mt. St. Helens. November 11, /Projects/BookV/Default.htm /Projects/BookV/Default.htm Mount St. Helens. November 9,

Mount St. Helens-The Sleeping Monster. November 12, Shadwick, Brian, and Susan Barlow. About Science : pp Eruption of Mount St. Helens. November 10, Mount St. Helens-The Sleeping Monster. November 12, Shadwick, Brian, and Susan Barlow. About Science : pp Teacher’s Guide to Stratovolcanoes of the World. November 12, Eruption of Mount St. Helens. November 10, ens#Buildup_to_disaster ens#Buildup_to_disaster