The Zuni-Bandera volcanic field covers an area of 2460 sq km along the Jemez lineament west of the Rio Grande Rift.  An older volcanic episode, mostly from vents along the Chain of Craters, took place from about 3.8-3.7 million years ago (Ma); the younger episode began about 1.7 Ma and has continued until the present, forming an extensive area of young lava flows known as El Malpais.  The youngest lava flow, the McCartys flow, traveled 60 km to the NE, fed by lava tubes up to 29 km long.  The McCartys flow was recorded in Indian legends and was thought to have been erupted about 1000 years ago, but radiocarbon dating indicates an age of about 3000 years Before Present.  The only other dated flow of Holocene age originated from Bandera Crater during the early Holocene about 9000-10,000 radiocarbon years ago.  An earlier flow, the massive Pleistocene Fence Lake lava flow, traveled as far as 90 km to the west.