I'm not sure how they are defining this region, but I've spent a lot of time intimately close with most of the Smith Rock Group. I've also hiked around Paulina Lake, Black Butte and ridden my bike from K-Falls north.

I'd never really thought of there being such a thing as the Crooked River Caldera. I'll need to have another look to see what they are talking about.

The whole area is geologically weird.

Near the base of South Sister there are obsidian boulders the size of vans with gorgeous of streaks of, I think, rhyolite running through them.

Smith Rock is such an amalgam of rocks. Mostly welded tuff with a good mixture of basalt and rhyolite and one large (two-story house sized) basalt boulder just sitting there away from all the rest of the basalt. Almost on the geologic Group W Bench. Then you don't see much of that until you get to Hole In The Ground. If you took that structure and dropped it in the Smith Rock area, it would absolutely not look out of place.

For those interested in riding, the state park outside of Bend (Tumalo) has a gorgeous hiker-biker area. Take the back roads from Bend to Redmond. Great views of the Cascade volcanoes. And lots of cows. For some reason, I get fascinated by cows when I've been on the bike a while.

However, as easy as the ride from Terrebonne to Madras may seem in a car, it's not. That is a hilly region and the nearest camp ground is Lake Simtustus about 10 miles northwest of town. Another big basalt boulder at the south end of the camp ground.