This area is part of a 2,200 square mile volcanic field near Flagstaff with more than 400 cinder cones. Sunset Crater is the youngest volcano; it exploded in AD 1065 and blanketed the entire region in thick, moisture preserving ash. Different prehistoric societies moved here to take advantage of the suddenly rich soil, so the area became a trading crossroads. More than 800 ruins – the homes and villages of the Sinagua and Ancestral Puebloans – have been found in this immediate area, and are now protected as Wupatki National Monument.