Hello and welcome to Prism of the past a weekly series about historical events, people and

situations from the fascinating to the forgotten.

I'm the Illuminati and today we've got another volcano to talk about one that I'm sure many of you have heard of Mount St Helens.

We're just going to dive straight into it, talk about the history of Mount St Helens, then

get into the massive eruption that occurred in May 1980.

Since this major eruption occurred about 40 years ago, we'll be able to talk about the long-term

effects of the eruption as well and perhaps

explore if another eruption seems likely in the future so let's get into it. So, Mount St Helens located in Washington State is primarily an explosive dasite volcano with a complex magma system.

A daside volcano simply means that the rock has a unique structure.

It's typically composed of 62 to 69 percent silica and typically lighter in color.

St Helens is also a stratovolcano which as we know from our very first episode of

Weird Wild World, Rest and Peace, it's an explosive volcano with steep-sided symmetrical

cones built up by the accumulation of debris from previous eruptions.

Strato volcanoes have plumbing systems that move magma from a chamber deep within the Earth's crust to vents at the surface.

It's the classic baking soda type volcano that many may have built in class.

Anyway, St Helens was formed during four eruptive stages about 275,000 years ago, according to the USGS.

Prior to about 12,800 years ago, Tefra, Lava domes, and pyroclastic flows were erupted, forming the older St Helens

Edifice, edifice being the main portion of the volcano built up by eruptions.

But a few lava flows extended beyond the base of the volcano.

The bulk of the modern edifice above the 1980 crater floor was constructed during the last 3,000 years

when the volcano erupted a wide variety of products from summit

to flank vents.

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