BrownsBay on Nostr: Yep, basalt (lava flow) of Oligocene epoch age (roughly 30 million years bp), ...

Yep, basalt (lava flow) of Oligocene epoch age (roughly 30 million years bp), resistant to erosion compared to the surrounding rocks. There's probably much more to the tectonic story of how these rocks were formed, where they formed, and how they got to be where they are. The photo screen cap shows the hills I think you're referring to. "Roadside Geology of Oregon (2nd ed.) by Marli Miller is an excellent book to have with you while traveling around Oregon.