Peak in Northern California, the range was quiet for more than a century. Then, on May 18, 1980, the dramatic eruption of Mount St. Helens shattered the quiet and brought the world's attention to the range. Geologists were also concerned that the St. Helens eruption was a sign that long-dormant Cascade volcanoes might become active once more, as in the period from 1800 to 1857 when a total of eight erupted. None have erupted since St. Helens, but precautions are being taken nevertheless, such as the Cascades Volcano Observatory and Mount Rainier Volcano Lahar Warning System in Pierce County, Washington. Geology The Cascade Range is made up of 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, like Mount Hood and Mount St. Helens, 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. The Ring of Fire is also known for its frequent earthquakes. The volcanoes and earthquakes arise from a common source: subduction, where the dense Juan de Fuca oceanic plate plunges beneath the North American Plate. As the oceanic slab sinks deep into the Earth's interior beneath the continental plate, high temperatures and pressures allow water molecules locked in the minerals of solid rock to escape. The water vapor rises into the pliable mantle above the subducting plate, causing some of the mantle to melt. This newly formed magma rises toward the Earth's surface to erupt, forming a chain of volcanoes (the Cascade Volcanic Arc) above the subduction zone. Human uses Soil conditions for farming are generally good, especially downwind of volcanoes. This is largely because volcanic rocks are often rich in potassium bearing minerals such as orthoclase and decay easily. Volcanic debris, especially lahars, also have a leveling effect and the storage of water in the form of snow and ice is also important. These snow-capped mountains such as Mt. Hood and Mt. Bachelor are used as ski resorts in the late winter, while in the summer they become popular hiking and mountaineering locations. Much of that water eventually flows into reservoirs, where it is used for recreation before its potential energy is captured to generate hydroelectric power before being used to irrigate crops. Because of the abundance of