Mount St. Helens

All About The Most Dangerous Volcano The U.S. Has Ever Had

Big image

Mount St. Helens

The Mount St. Helens volcano is on the border of the Juan de Fuca and the North American plates. The formation of the volcano took a long time! Before the eruption, the Juan de Fuca plate was colliding with the North American plate. It was a continental-ocean convergent boundary. A continental-ocean convergent boundary is when a continental plate collides with an oceanic plate. In this case, the Juan de Fuca plate was the oceanic plate, and the North American plate was the continental plate. When a continental plate collides with an oceanic plate, the oceanic plates goes through the process of subduction. Subduction is the process by which an oceanic plate goes under the continental plate because the oceanic plate is more dense than the continental plate. In this case, the Juan de Fuca plate was descending beneath the North American plate, and it melted when it reached the asthenosphere. Because the Juan de Fuca plate was an oceanic plate and it mixed with the magma in the asthenosphere, the magma in the asthenosphere became gaseous and it was filled with water. Then, the volume of the magma increases, so the density decreases. Therefore, magma started to rise to the surface. It takes tens of hundreds of thousands of years for the magma to reach the surface, but it was getting closer every year. Because of the melting, bubbles of gasses were produced, making magma rise closer to the surface. Because that happened, the pressure was raised even farther. The water, the gas, and the magma, mixed together, created a deadly explosion.


Mount St. Helens is a composite, stratovolcano. This is true because a stratovolcano is a tall volcano that is composed of one layer of volcanic ash and hardened lava. Stratovolcanos create explosive eruptions. Composite volcanoes form from explosive eruptions of pyroclastic material followed by quieter flows of lava. Composite volcanoes form over hundreds of thousands of years.


There are many parts of the volcano as well. At the top of the volcano, there is a gas/steam plume. This is where the gas and steam of the volcano came out. Near the gas/steam plume, there is the Lava Dome and the Sugar Bowl Dome where magma exploded out of its magma chamber. There is also the Pumice Plain, where pumice destroyed the forests and areas. The gas/steam plume is the crater, the Sugar Bowl Dome and the Lava Dome are part of the vent, and the Pumice Plain was the result of the eruption.


On March 20, 1980, several small earthquakes were detected in this area, and people became interested in this region. Between March 20th and May 18th, over 2,800 earthquakes were detected in that area. A lot of people came to see this place because it was becoming a tourist attraction place. Days leading up to the eruption, the Washington governor had to call the national guard to keep tourists from going near Mount St. Helens.


On May 18, 1980, at 8:32 in the morning, the volcano erupted. There was an earthquake there that measured 5.1 on the Richter scale, and that's what caused the volcano to rattle and erupt. There were 57 people killed, and most of them died because of breathing in hot gases. Because of the blast, the volcano's height was reduced by 1,314 feet. In the state of Washington, over 900,000 tons of ash was cleaned. There was 230 square miles that the volcano affected, which was 110,000 acres. Over 7,000 animals were killed as a result of the eruption. These are some of the reasons why the 1980 eruption of Mount St. Helens was the deadliest and most economically destructive volcanic event on U.S. soil ever.


Today, Mount St. Helens is an active volcano. An active volcano is a volcano that has erupted in the past 10,000 years, and Mount St. Helens last erupted in 2008. It is a tourist attraction in Washington. But remember-if someone tells you that there is a volcano nearby, listen to them and go far away. Go far, far away.

Big image