There have been volcanoes in the Oregon area for 30 Million years ago, blasting huge amounts of ash into the sky. Winds and rivers carried the ash to where the John Day Fossil Beds National Monument now lies. This volcanic ash built up, layer after layer, continually burying the marshes and forests that flourished in the moist and warm tropical climate of the period.
The heavy stroms that rain down here today carve gullies into the soft layers of ash and, over time, have created the striped landscape of Painted Hills. The yellow and red layers owe their colour to eroded volcanic materials, while the dark blurry flecks are the remains of dead vegetation.
From the website: bernhardedmaier.reacore.net/site/en/what.pictures.article...