The United States Geological Survey - USGS - one of my all-time favorite sites - full of amazing stuff about the Earth. Very informative!
Amazingly, we have a very active spreading ridge just off the coast of Oregon and Washington! It's called the Juan de Fuca Ridge, and there's an active volcano right on the ridge called the Axial Seamount. Check out this link to learn more about it!
Oregon wasn't always here. Most of Oregon is stuff that has been scraped off the bottom of the ocean floor and added to the edge of the continent! This process is called 'accretion' and the link above is a page with some interesting information about how accretion works.
Virtual Earthquake (advanced)
USArray - network of seismometers that is moving across the country. Check out some of the animations of the array as seismic waves from different earthquakes move across the US. Fascinating. Click on the "View GMVs:" link to pick the animation you'd like to download.
Make sure to read the tutorial pages first and watch the short step-by-step animations that explain how the array works.
The Ripple Tank! Check out this cool 'applet' showing how waves act in different substances. This can help understand how seismic waves travel through the layers of the Earth! Click on the link, and then click on "Ripple Tank (2-D Waves) Applet."
Volcanoes in Portland (Click "Open" and be patient as it is a very large PowerPoint. Note that on some of the slides the pictures do not show up. We are working on that! Saving the PowerPoint does not allow you to see the animations.)