The Painted Hills in Oregon is one of the three units of the John Day Fossil Beds National Monument. They are listed as one of the Seven Wonders of Oregon. Once this area was a river flood plain with a warm tropical climate and an abundance of plants forming lush forests with exotic prehistoric animals like sable tooth tigers. An abundance of fossil remains makes the area particularly important to vertebrate paleontologists. Over a period of 35 million years the landscape transformed several times due to volcanic eruptions and climate changes. Layers of ash and different types of soil mixed with minerals and plant material and eroded causing the unique coloring of the Painted Hills landscape. Grey material is mudstone, siltstone, and shale. Red material is iron-oxide and yellow material consists of iron-oxide and manganese-oxide. The black spots are manganese composites caused by ancient plant material. The clay can absorb lots of water and is almost impenetrable by plants. When the clay dries up it brakes down into small pellets causing the colors to fade because the light is reflected in all directions. Once the clay is completely saturated by water, the surface smooths out completely and the coloring becomes much more vivid.
