I recently took an afternoon and visited the Painted Hills, near Mitchell Oregon. Some of the hills in this area are banded with color (reds, yellows, lavender). The black soil is lignite that was vegetative matter that grew along the floodplain. The grey coloring is mudstone, siltstone, and shale. The red coloring is laterite soil that formed by floodplain deposits when the area was warm and humid (this was not recent. The current climate is fairly dry, with around 11" of precip a year).

Gallery