The forested Sacramento and Sierra Blanca Mountains (lower left) of central New Mexico form the eastern edge of the Rio Grande Rift Valley, a rift zone that extends north-south through central New Mexico. Snowcapped Sierra Blanca Peak rises 12 003 feet (3659 meters). Fewer than 1000 years ago, lava erupted from Little Black Peak, a tiny volcanic center at the northern end of the dark, smooth, somewhat linear lava flow (left center). A partial view of the Hondo River drainage basin appears south of the east-west aligned Capitan Mountains (center of the photograph.