Sahalie Falls between Eugene and Bend on Hwy. 126. Over the past 6000 years, six basalt flows have tortured the McKenzie River, damming it at Clear Lake, squeezing it into a gorge at Sahalie Falls, and burying it altogether on the dry riverbed near Tamolitch Pool.
Obsidian Flow, Newberry National Volcanic Monument, near Bend, Oregon. You can hike thru the lava flow where most of the rocks are obsidian...kind of like a sharp, black glass rock. When a piece falls or tumbles down a hill, it sounds almost metallic. The flow is large, covering several acres. You can hike up onto the top and down paths over the entire flow. Very other-worldly.