Photo @stephen_matera // Volcanic rocks, known as black boulders, in a wash in the Bentonite Hills near Caineville, Utah. This area of exposed bentonite is just outside the boundary of Capitol Reef National Park and is a colorful remnant of fine volcanic ash and silt deposited during the Jurassic period 140 million years ago. Follow me @stephen_matera for more images like this from Utah and around the world. #capitolreef #bentonitehills #desert #blackboulders