The Three Sisters
In 1980, when in Portland, I'd see the smoke from one to the north in Washington that had blown its top. It's a modern city, Portland, and yet when you see smoke rising from a mountain you have always seen with one shape, a mountain you always knew was a volcano, but that now has been reshaped by a massive, shocking explosion, suddenly you don't feel so modern nor so far from primitive forces.
When you understand their volcanic reality, you look at these peaks differently. You understand more that the forces behind making one go from dormant to active are little known. Some of the warning signs can be observed with science; but in the end, it does what it does. For all the humans, who want to think they can control everything, volcanoes are a reminder that they don't.
I often think how this area must have seemed to the peoples who lived here when the volcanoes were all more active. They sometimes spewed lava for miles not to count the ash and all the cinder cones and fumaroles that cropped up. The largest such example of awesome power in our Cascades would be the volcano that left behind Crater Lake-- Mount Mazama literally blew its top leaving behind the beautiful crater that today is one of Oregon's scenic wonders.
The Native Americans created legends about the exploding mountains and the purposes behind their explosions. I used one of those in my second Oregon historical romance.
There is one more geologic mystery of sorts-- although some think they know the answer. The Metolius River emerges from the ground fully formed (although there are springs that add to its size as it flows north. The water stays the same temperature year round (cold very cold). It is a place we have camped with our families over many years and where we still stop when we have time on our way back from Eastern or Central Oregon. If there be such things as vortexes (energy high spots), it's definitely one, a place for beauty, meditation, healing, hiking, and fishing (catch and release).