 Although the largest volcanoes like Mount St. Helens get the most attention, the Cascade Volcanic Arc includes a band of thousands of very small, short-lived volcanoes that have built a platform of lava and volcanic debris.Rising above this volcanic platform are a few strikingly large volcanoes that dominate the landscape.The Cascade volcanoes define the Pacific Northwest section of the Ring of Fire, an array of volcanoes that rim the Pacific Ocean.