Clear Lake Addendum

These aren't my photos, so they don't count as part of the Geo 365 project- I'll label them that way so this comes up with this morning's post, though.

This is a view in FlashEarth of the area, backed out and moved eastward from this link. See that line of cones? Ed Taylor, from whom I had many great geology classes, often talked about lines of vents in the Central Oregon Cascades, and that there is one of them. It's almost certainly fault-controlled- the fault being a zone of weakness that rising magma can push into and follow more easily. It looks as if the eruption of the flow that created Clear Lake came from about the middle of that line, just based on its shape, but I'd be careful of making that as an actual claim. I haven't checked it on the ground, so I can't claim confidence as to where the actual vent was/is.

And to preempt possible confusion, that line is not the Cascade Crest- that lies a bit farther east- the dotted line on the capture below marks the boundary between Linn and Deschutes Counties, and lies on the topographic (though confusingly, not the hydrological) divide of the Cascade Crest. Because these young flows are so fractured and permeable, groundwater may actually flow freely across what appears as if it *ought* to be the hydrological divide.

Another interesting feature, just west of the divide, and to the east of the northern end of the little line of vents, is Hayrick Butte, a tuya, or sub-glacial volcanic eruption. Taylor did not like this idea one little bit when it was presented at an afternoon seminar in the mid-80's, but it seems to have gained widespread acceptance now. Eric Klemetti has some nice photos and a good discussion here.