The Valles caldera, also known as
the Jemez caldera, is a large volcanic
caldera located west of Los Alamos, New Mexico.
It last erupted a little
over one million years ago. That
eruption ejected enough material to
cover the state of New Mexico to
a depth of six feet, corresponding
roughly to a cube six miles
across. The caldera
is easily visible from space, and
from the ground it appears as a large,
bowl-shaped depression in the
Jemez Mountains of north central
New Mexico. It was (at the time of
my last visit) known as the Baca
Ranch, and was used for cattle,
horses, and sheep. The area also
has a large number of hot springs.
Volcanism in the Jemez range,
in conjunction with erosion by the
Rio Grande, is responsible for the
complex and beautiful topography
and geology of the
Los Alamos and surrounding mesas.
The Jemez volcano is just one of
a number of volcanic structures
throughout the state of New Mexico. The last
eruption occurred in the state a
thousand years ago, forming what is
now the Valley of Fires, a recreation
area on Highway 380, west of
Carrizozo, New Mexico. Not reassuringly
for Los Alamos, the Jemez volcano is
considered dormant rather than
extinct, and may erupt in the
(albeit distant) future. The area
is geologically active, and suffers
occasional, very minor
earthquakes.
The caldera is an
impressive sight, particularly
in the summer. Not only did they
raise animals on the ranch, but they
raise thunderstorms over
the caldera as well, which billow up
from the warm, moist pastures
and move eastward
towards Los Alamos and the Rio Grande
valley. Shortly after I left
New Mexico, the government purchased
the land to convert it to a monument
and it is now known as the Valles
Caldera National Preserve. It can
be reached from Los Alamos by heading
west on West Jemez Road, and turning
north on Highway 4, into the hills.
(Turning south on Highway 4 takes you
to Bandelier National Monument.)
The caldera itself is not yet
accessible, but is still an impressive
sight even from the side of the road.
Some of this information was
adapted from volcano.und.nodak.edu and
exhibits at the Los Alamos Historical
Society museum.