The principal structure of the southeastern Datil-Mogollon area is a large central-type volcano, Mount Taylor, that rises to . It is surrounded by numerous smaller volcanic centers and volcanic necks with extensive lava-covered mesas and valleys to the south. The largest mesa is long and about wide, with an upper elevation of above the surrounding plain, and is capped with about of lava. The ancient lava flows extend southward into the Mexican Highlands section of the Basin and Range Province and consequently that border of the Colorado Plateau Province is ill-defined.