Mount Saint Helens

Brittany, F4

Where?

Mount St. Helens is on a destructive/convergent plate boundary. The Juan De Fuca plate, which is located at western side of the North American Plate subducts beneath the North American plate. This means that Mount Saint Helens is on a destructive plate boundary.
It is located in the United States, at the western side of North America. The United States is an MEDC so has plenty of resources for prediction and prevention of tectonic hazards.

How was the volcano formed

A destructive/convergent plate boundary which means movement in the mantle and convection currents. This moves the 2 plates towards each other.

In this case the Juan De Fuca plate is the oceanic plate and the North American Plate is the continental plate. The Juan De Fuca plate is denser than the North American plate, due to this the Juan De Fuca subducts beneath the North American plate.
The plates rub against each other causing friction, sometimes the grinding of the 2 plates get stuck, and this is then released as an earthquake.
As the Juan De Fuca goes deeper, the friction and heat from the mantle melts the rock.
This creates magma. The magma rises to the surface as it is less dense. This then creates a Stratovolcano, which is only found on or near destructive plate boundaries.
Magma rises out of the magma chamber. It rises out of the crater/caldera causing an volcano eruption. Magma that leaves the volcano is called lava.

Eruption Case Study 18 May, 1980.

Primary impacts of the volcanic eruption:

There was hot ash and gas given out from the volcano during the eruption, known as the Nuée ardente. Nuée ardente - it is a french phrase, literally meaning the ‘glowing cloud’ which describes the cloud of volcanic debris formed during the eruption.
Poisonous gases were emitted. E.g (Sulphur dioxide and Hydrogen Sulphide).
Lahars - a destructive volcanic landslide or mudflow, consisting of a mixture of volcanic debris,mud, rock and water covered an extensive area around the volcano.

Secondary impacts of the volcanic eruption:

Economic

The ash destroyed forests and logging camps, blocked rivers ruining famous fishing sites and caused major flooding. This also lead to the loss of livestock and crops. This created economic losses for people.

Social

The poisonous gases emitted killed 63 people.
The flooding destroyed roads, railways and railway bridges. This destroyed the transportation to places, isolating communities.

Environmental

Remains of the eruption were washed downstream blocking and ruining the barge transport on the Columbia river. This made it harder for transporting equipment and it makes it prone to flooding, as the river is clogged up with the remains.

Human Response:

Short term responses:

Long term responses:

The volcanic eruption left fertile soil, improved due to the ash deposits. The fertile soil has been put to good use in agriculture, such as farming.
The volcano is now carefully monitored. Some of them are prevention schemes, seismic monitoring network, developing models of the magmatic system beneath Mount Saint Helens and forecasting eruptions and detecting explosions.
Tourism has now increased, due to the attraction of Mount Saint Helens. This helps boost the local economy.
Using geothermal energy to generate electricity for factories.
Deposits of Sulphur,zinc,diamond,gold,silver and sediments to make bricks have led to mining prospectors investigating the area.

Bibliography

Fretwell,M and Kelly,D. (2012) Complete Geography for Cambridge IGCSE. Oxford: Oxford University Press, 356 pages.

[Accessed at 24 January 2017]

volcano.oregonstate.edu,(2017).(OSU) Oregon State University.[online]Available at:http://volcano.oregonstate.edu/what-were-effects-people-when-mt-st-helens-erupted [Accessed at 24 January 2017]