Closeup of Hat Rock, a landmark along the Columbia River northeast of Hermiston, OR. Hat Rock shows up in the Journals of Lewis & Clark. What I like about it (apart from its fez-like shape) are the thin-fluted columns about the thickness of a baseball bat. This is a characteristic of the Pomona basalt flow, one of the youngest (11 million years) and rarest of the Columbia River Basalt Group flows.