Most lava domes in the Cascades occur in clusters or surrounding just a few major volcanic centers. There are roughly 190 known domes in the state of Oregon, with 40 located near Mount Jefferson, 22 near the Tumalo volcanic highland, 28 near the Three Sisters, and close to 60 surrounding Mount Mazama. Hayrick Butte, however, is more isolated from other volcanoes. Hayrick Butte, along with Benchmark Butte, formed more than from any major stratovolcano. Hildreth (2007) likewise writes that Hayrick is clearly separated from major clusters or evolved centers.