The Cascade Range is one of the most accessible spans of active volcanism on Earth. Running from southern British Columbia to northern California, many of the volcanoes are located within a day's drive from major cities like Seattle, Portland, Sacramento and San Francisco. If you've never visited a volcano, it is hard to describe what it is a like to see one in person. They're big. They are imposing. Many times they are covered with snow and ice. Sometimes they are just a big hole in the ground because they erupted so violently. Sometimes there are ancient lava flows that look as if they erupted yesterday. Visiting a volcano should be on everyone's life list.
Over the next few weeks, we'll be taking a tour of the modern Cascade Range volcanoes from north to south. Using some of the stunning imagery from the European Space Ageny's Copernicus program that utilizes the Sentinel-2 Earth-observing satellite to capture high resolution images of almost everywhere on the planet. These images span from visible light to infrared to surface moisture. The Copernicus browser for these images is possibly the ultimate rabbit hole for people who love Earth sciences. If you'd like to see the high resolution of the images below, you can check them out here.
The Cascade Range exists because the Juan de Fuca plate (and its broken brother, the Explorer Plate) are sliding down underneath North America in a process called subduction. As that oceanic plate goes down, it heats up and releases water that causes the mantle rock beneath North America to start to melt. This is magma and it rises through the North American crust to form volcanoes. Because this process mostly happens at the same depth as the Juan de Fuca plate goes down, the volcanoes occur as a line that is somewhat parallel to the edge of North America.
You can see that align in the map of the Cascades below (click here to see a higher resolution version). There are a few exceptions like Mount St. Helens that is closer to the coast than average and Newberry Volcano as well as Medicine Lake volcano that are further. This can mostly be explained here by "tectonics gets complicated" and we'll save that for another day.
