A friend of mine posted this video to my Facebook page and I thought it was awesome enough to warrant sharing on the blog. What I find really fascinating about this video is that you get to see how the basalts get that pillow like shape. As the basaltic lava flow comes in contact with the water, it quickly quenches into that bulbous shape. The lava continues to build-up in the pillow, and like blowing too much air into a bubble, basically bursts open and the process repeats itself.
What’s even cooler is that, through a process called obduction, those pillow basalts get heaved up onto the continent. Think of it as the opposite of subduction; instead of the pillows getting swallowed by the oceanic crust as it dives under the continental crust, it gets uplifted onto the land. In what is surely a perverse joke by nature, some of these pillow basalts can be found in Oregon. It’s as if nature decided we didn’t have enough basalt from the Columbia River basalt group, so it gave us sea-floor basalt as well.
Glacial Till 
Wow… and the diver was *in the water* watching that happen!
Since the Coast Range basalt predates the CRB in both formation age (~60 ma) and accretion age (~45-50 ma), I think the CRB is more likely the perverse joke.
On the geological timeline, that’s absolutely true. But I was thinking about it in a “half-dozen in one hand” and “six in the other” sense. Although I think the CRB’s are much more voluminous.
In terms of volume, hard to say… probably depends on whether you consider the intrusive portion of accreted crust as “basalt.” But the terrane extends from about Roseburg to S. Vancouver Is. (S/N), and W. Cascades out to Cascadia subduction zone (E/W), so it’s certainly not small in volume. It’s just that it’s mostly hidden under younger rocks.
You’re right on that point. I’m trying to find information about how much accreted basalt Oregon contains, but I’m not getting much aside from page after page of CRB’s. Even on the internet you can’t get away from it!
Accreted- “allochthonous-” basalt is found in several different parcels in the Blue Mts and Klamath/Siskyou chaos, in addition to the Coast Range. The rest erupted more or less in place- CRM, Steens Basalt, High Lava plains basalt, Cascades- Western and High (Ed Taylor estimated 90%+ of Cascades lavas were basaltic), and Newberry area, which is probably best seen as confluence/combined influence of HLP and Cascades magmatism/volcanism.
I have commented several times that unless you’ve spent plenty of time exploring Oregon, it’s tough to comprehend just how thoroughly volcanic this state really is.
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