Located in the transition zone between the moist, heavily-forested west side of the Cascades and the drier bunch grass prairies of the east, Tom McCall Preserve comes into spectacular bloom every spring.

Lava flows, catastrophic floods and volcanic ash deposits shaped a mound-and-swale topography that perplexes the experts. Earthquake sorting, freezing and thawing, erosion, soil accumulations by plants and wildlife burrowing activities have all been suggested as having caused the mounds.