Saturday, August 30, 2014

Geo 730: August 30, Day 607: Dana Being Cool

In the very left bottom of the topo map below, you can see a three-way intersection, with one road following Quartzville Creek off the bottom, one following Canal Creek ~north, and one running diagonally up the hill between the other two, and toward the center of the map.After leaving Yellowbottom, head up Quartzville road to that three-way intersection and take the middle gravel road (the other two are paved) up the hill.
The spot near the center marked "Gravel Pit" is the location for the photo. It's an anomalously young cinder cone; I'm told there's a spot where you can see that it overlies glacial drift, which constrains the age to the last 1.5 million years or so. This is a puzzle, because most volcanism outside of the High Cascades in Oregon ended by the Pliocene, about 5 million years ago. I don't know if anyone has done more detailed studies on this or other anomalously western post-Pliocene eruptions, and I don't know enough to responsibly speculate about the magma source. So I won't, other than to point out, there it is.

Oh, and Dana's always cool, but especially in this photo. Cinder cones by their nature are very porous and permeable, just piles of loose volcanic cinders. They also have a large mass, so during the winter, they cool slowly, and during the summer, they warm slowly. I imagine if you were up on this hill in the winter, you'd find areas where snow melts off quickly, perhaps immediately, where warm air rises up out of the cone to the ground's surface. But during the summer, cold air rushes out of the base as a noticeable chilly breeze. In fact, the last time I was here, I didn't even walk up the hill from the road, but I could feel the cooler air, at knee level and below, coming down from vents like the one behind Dana in the photo. When you get close to one, as she is here, it can actually be uncomfortably chilly, especially once you're acclimated to hot summer days. I don't know, but I'd like to think that's why she's laughing here.

Photo unaltered. July 7, 2012. FlashEarth Location.

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