>>3088424In P6020088 you can see Beacon Rock, Crown Point Lookout, and Rooster Rock, but Larch Mtn isn't visible. Pic related shows all 4 formations, which each have their own awesome stories.
Beacon Rock is the neck of a former volcano, the crystalline igneous intrusion that formed in the magma chamber was more resistant to weathering than the surrounding clastic igneous rocks, so now it's left standing.
Rooster Rock is the same way: crystalline igneous rocks. I think it was part of the volcanic bulge of the same volcano as Beacon Rock, and was carried into the valley by a landslide but don't quote me on that.
Larch Mountain is a shield volcano, so its magma was more mafic in composition and less viscous, which is why the lava flows so much faster and spreads forming the dome. It's interesting how the magma forming from this part of continental lithosphere was felsic/intermediate during the time of the Beacon Rock volcano, and mafic during the Larch Mountain formation.
I believe the Crown Point Vista is built on the flat exposed section of one of the Columbia River Basalt layers.
