With Emphasis on the Cascade Range Volcanoes of the Pacific Northwest
The outer layer of the earth is composed of large slabs of "lightweight" material known as the crust. This crust "floats" on a molten layer below it known as the mantle. These floating slabs, known as plates, are in motion. Where two or more of these plates meet, earthquakes and volcanic activity is usually present. By looking at the map of volcanoes around the world, a general outline of plates become evident. The most noteworthy concentration of volcanoes forms a ring around the Pacific Ocean. This area is perhaps the most seismically active on earth. The arrangement of volcanoes appropriately gives the name "Ring of Fire" for those fringing the Pacific.
Mount St. Helens WebCam
Live Video Cam Courtesy of USDA Forest Service
Click HERE to view the latest seismograms from St. Helens.
Smithsonian Institution Volcanoes of the World
USGS Volcanoes of the World
USGS Cascade Volcano Observatory
Cascade Volcanoes at a Glance (USGS)
Montserrat Volcano Observatory
Philippine Institute of Technology
Hawaii Volcano Observatory
Alaska Volcano Observatory
Long Valley Caldera Observatory
Yellowstone Volcano Observatory