The Painted Hills are part of the John Day Fossil Beds National Monument located near John Day, Oregon. The ground is like a puzzle. A long streak of colour breaks off, then seems to continue in the next hill, but at a different level. To connect the pieces, look for similar colour, thickness, and sequence in a series of layers.
Ash and pumice from the ancestral Cascades and local volcanoes buried this area layer by layer. The colourful layers were deposited 33 million years ago. Soil formation processes affected each layer differently. Clays were formed and deeply buried, turning to stone. Underground forces lifted and faulted the strata, interrupting the symmetry.
The red in the Painted Hills is from rusty iron minerals, oxidized by long exposure. The golden layers reveal a mix of oxidized magnesium and iron, metamorphic claystone minerals. Black hash marks are rich with manganese. Each of the colours represents a different geologic process. The valley is a gently contoured theatre of geologic change, with erosion from rain the latest sculptor. There is no plant life present on the Painted Hills. (Text source taken from plaque at National Monument).