Yup, and people do not realize how lucky folks were the Teton Dam collapsed while being filled instead of 130' below the top. The next 100' was a Hell of a lot more water than the first.
There was also similar "bedrock" there that was the problem. And it was volcanic tuff as I recall with better properties than foliated basalt.
That's an interesting statement, since basalt can't be foliated - it's igneous. But never mind that - the bedrock at Teton wasn't tuff anyway, it was rhyolite, as is much of the bedrock in Idaho.
The fact is that the bedrock at Teton had fissures (typical of rhyolite) that weren't grouted sufficiently (if that is even possible), and the dam failed from low on one side. So the bedrock under Teton dam was not better than, or even similar to, what is under Oroville. And the dynamics of that dam failure were not in any way comparable to what is happening at Oroville (at this time).
Not long after the collapse of the dam I was taking an advanced geology course not too far from the site. The class took a roadtrip to look at what happened. That was a long time ago and my memory could have slipped a bit.
The volcanic rock at the dam site consists of hard, welded, rhyolitic ash-flow tuff dated at 1.9 million years. Along the axis of the dam, the tuff ranges in thickness from about 50 feet in the left side of the channel section to more than 500 feet under the right abutment. The tuff is underlain by sedimentary rocks which are not exposed along the dam axis but were encountered in exploratory drill holes. On the left side of the canyon bottom, an erosional remnant of an intracanyon basalt flow overlies the tuff. On the right side of the canyon, the basalt and tuff are overlain by a thick accumulation of young alluvium. A thin layer of older alluvium is also intercalated between the tuff and the basalt.
The tuff in the right abutment is foliated and strongly jointed. The joints consist of both high-angle and low angle joints. The dominant high-angle joints are spaced from a few feet to about 10 feet apart, whereas the low-angle joints are generally widely spaced except in the upper 70 to 100 feet of the abutment. There the closer spacing results in a platy structure. After the dam failure, some of the joints were observed to be tight, others open as much as 5 inches. Some joints are lined with calcite, others are filled with silt and rubble.
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So there is rhyolite in it, but it is welded tuff.
I did confuse the foliated "bedrock" at the Oroville dam for basalt... as this is the initial filling of the dam all the way to overflowing it is putting a new test on lousy underpinnings.
Mark Begich, Joaquin Jackson, and Heller resistance... Three huge reasons to worry about the NRA.
