|Mt. Shasta from Interstate 5 in the vicinity of Red Bluff and Corning. Photograph by Mrs. Geotripper|
I was thinking about that as we drove north on Interstate 5 in the northern Great Valley on the first day of our exploration of the Pacific Northwest and northern Rocky Mountains. We were a band of 19 students and staff on a two week journey, camping our way across some of the most spectacular landscapes on earth. Looking out the windshield I couldn't help but think that we were headed right at some particularly young and active volcanoes, such as Mt. Shasta (above).
|The Sutter Buttes north of Sacramento in the Great Valley. Photo by Mrs. Geotripper.|
The subduction zone is disappearing in geologic terms as it replaced by the growing San Andreas fault (don't panic too much, it's happening at a few inches a year). Volcanoes at the south end have been going dormant and then extinct. Once possible example is the unusual set of hills in the midst of the Great Valley north of Sacramento. The Sutter Buttes are the eroded remnants of a volcano that erupted around 1.6-1.4 million years ago. They're west of the main axis of the Cascade range, but then again so is Mt. St. Helens. Most research suggests that the volcano is more closely related to volcanic fields in the California Coast Ranges.
|Lassen Peak from the west. Photo by Mrs. Geotripper.|
|Black Butte on the flank of Mt. Shasta. Photo by Mrs. Geotripper.|
We passed one more prominent volcano before we reached the end of the road on the flanks of Mt. Shasta. Black Butte is a large looking volcano when viewed from Interstate 5 around Mt. Shasta City, but is a very small volcano compared to the adjacent edifice of Mt. Shasta (it can be considered a part of Shasta). Like Lassen, it is a plug dome that erupted about 9,800 years ago.