Mount Hood Seismicity
Following Mount Fuji, our very own Mount Hood is the second most climbed mountain in the world, with over 10,000 people summiting a year. Mount Hood can look like a different mountain from different vantage points, sometimes appearing very sharp and pointed, sometimes much more supple like it does from the Columbia River Gorge.
The tendency for mountains to “create” their own weather has led wilderness safety organizations like NOLS to emphasize that every river is a new river every time you step in it. On a day last month when I climbed to the Sandy Glacier Ice Caves, I experienced some very favorable and some unfavorable conditions for wayfinding. Check out the two photos below of a white-out compared to the sunny conditions just moments prior. Can you spot the entrance to the caves on the side of the glacier?
The Sandy Glacier Ice caves were discovered as a passage carved by a subglacial stream several years ago. It is the longest ice cave in the lower 48 states. Since the glaciers no longer grow in the winter, the caves continue to expand their walls in the summer. Just like tree rings, the stratified walls tell a story of continuous melt and build.
We are constantly revising what we know about Mount Hood. For example the Pacific Northwest Seismic Network has created this database of triangulated earthquake points. There have been 128 tiny earthquakes on our mountain in the past 30 days (shown as yellow dots in the image below)!
Mount Hood is just one peak in the Cascade volcanic chain and the Pacific Ring of Fire, which also includes Mount Rainier, Mount St. Helens, Crater Lake and the Three Sisters. All of these mountains have had illustrious histories of volcanic activity. As this chart reminds us, even a magical experience like the one I had in the Sandy Glacier Ice caves is just a tiny blip in geologic time.