Painted desert and Petrified forest

North and south of I-40 just east of Holbrook, AZ is a fascinating geologic area that dates back to late Triassic times over 200 million years ago —the Petrified Forest National Park. Back then this area was warm, humid, and swampy, with lush tropical forests of conifers and cycads and great expanses of water — the perfect environment for early vertebrates like large carnivorous fish and huge amphibians, and the more recently evolved reptiles.

The portion north of the interstate is the Painted Desert — a collection of mesas and hills with vibrant bands of colors from their iron and manganese content. The sediments here are imposed of siltstone, mudstone, and shale, and are easily eroded by wind and water to reveal the stratified layers below…