7. Volcanoes of the Cascade Range.

Vineyard Mt., Larch Mt., Mary’s Pk.

Corvallis

ActiveDormantExtinct

7. What Oregon volcano is still considered active (erupted in last 200 years)?

7. Answer: Mt. Hood

Mt Hood is an active stratovolcano!

solid

Upper Mantleplastic

What is in the crust? 47% Oxygen 28% Silicon 8% Aluminum 5% Iron 4% Calcium 3% Magnesium 2% Sodium

Crust

Continental crust is thicker and less dense than oceanic crust.

The Crust is made of solid plates that “float” on the Mantle.

8. What are the two most common chemical elements in the earth’s crust?

8. Answer: Oxygen (47%) and Silicon (28%)

8a. What are the two most common chemical elements in lava?

8a. Answer: Oxygen (47%) and Silicon (28%)

Mt Saint Helens – April 1980

Mt. St. Helens

Eruption in May 1980

Cartoon by Sidney Harris

Mt Saint Helens – June 1980

Belknap Crater

Little Belknap

Shield volcanoes in the Cascades

This lava flow came from Little Belknap 1300 years ago.

Lava Flow at McKenzie Pass

A’a’ – blocky lava

9. What type of volcano is this?Mt Jefferson is an extinct stratovolcano

A 4 inch “bulge” (probably caused by magma) has developed over the last 4 years on the west side of South Sister. (as of 2004)

ERUPTION LIKELY?

Earthquake activity by year at Three Sisters showing depth

NASA photo October 1994

Could South Sister Erupt Soon?

Possible Hazards from an Eruption of South Sister - USGS

Corvallis

EugeneBend

8. Summary – Oregon’s complete geologic map.

Complete surface geologic map of Oregon…very complex!!!

Cartoon by Sidney Harris

Where was this photo taken?

Acknowledgement: USGS, Volcanoes Web Site, Geology of Oregon, and other public web sites for diagrams and photos