An unusual circular depression crowns the top of the Jemez Mountains
near Los Alamos, New Mexico. This feature formed when the roof of a
huge underground magma chamber collapsed and hot, suffocating volcanic
ash spread across the surrounding landscape. The circular depression is
called the Valles Caldera and is outlined by a dashed line below. s domeshaped
hills composed of solidified volcanic lava. This photograph ()
shows part of the depression, including the curved outer wall to the right