Volcanoes

Welcome to Washington - the 42nd State

Why are we in Washington?

How are volcanoes different in Washington than Hawaii?

The evergreen state

Space needle – built for the 1962 World’s Fair

Pike’s place market – you can get anything from fish to tulips

Honey – I’m home

Cascade Range

• We’re in Washington because of the volcanoes in the Cascade Range

http://en.wikipedia.org/wiki/Image:Cascade_Range-related_plate_tectonics.png

Historic 1847 painting

• The tiny Juan de Fuca plate is subducting under the North American Plate – this created the chain of volcanoes

What mountains make up the Cascade Range

• Mount Thielsen

• Mount Stuart

• Mount Lassen

• Mount Shasta

• Mount Rainier

• Mount St. Helens

Mount Thielsen: Mount Thielsen is one of the "pointiest" mountains in the world, but the firm rock

of the summit pinnacle makes it an easy climb.

Mount Stuart is a massive rocky pyramid that utterly dominates the

view from Longs Pass.

Lassen Peak: The volcanic moonscape of the summit crater.

Mt. Shasta and the prominent "heart", surrounded by narrow snowfields, from the town of Mt. Shasta.

The massive, icy form of Mount Rainier in the classic view from the Paradise Inn area on the

south side of the mountain.

Mt. St. Helens before the blast

And after – what happened

• Mt. St. Helens is on an ocean-continent subduction boundary (the Juan de Fuca plate is subducting under the N. American plate). Mt. St. Helens is an active stratovolcano.

May 18, 1980

• Graphic shows the amount of material displaced by the 1980 blast

May 18, 1980 activity

• 1300 ft of the summit vanished

• Debris avalanche was more than half a cubic mile

• 235 square miles were devastated by blast cloud and volcanic debris

• 57 people dead or missing

• Miles of road and bridges destroyed

• Crater left was 1.2 miles wide, 2.4 miles long, 2000 ft deep

Mudflow-damaged house along the Toutle River.

Downed trees from blast – note people in lower right

Another view of lahar

January 2007

25 years after the eruption

Current eruption over

• The nearly three and a half years of eruption at Mount St. Helens is over for now and on July 10, 2008, scientists lowered the volcano alert level from Advisory to Normal and the aviation color code from Yellow to Green.

• Mount St. Helens reawakened in October 2004 when four explosions blasted steam and ash up to 10,000 feet above the crater.

• Growth of this lava dome continued until late January 2008.

• Five months have passed with no signs of renewed eruptive activity. Earthquakes, volcanic gas emissions, and ground deformation are all at levels seen before the eruption began.

Next eruption?

Just in case