The image is a photograph of a sign on a stone wall. The sign is rectangular in shape and has a white background with black text. The text on the sign reads "An Unconformity: Rocks of Ordovician and Silurian Periods are missing in Grand Canyon. Temple Butte Limestone of Devonian age occurs in scattered pockets. Redwall Limestone rests on these Devonian rocks or on Muav Limestones of much earlier Cambrian age." Below the text, there is an illustration of a rock formation with a red arrow pointing to the right. The illustration is in black and white and shows the different layers of the rock formation.