Bandelier Geology

volcanic map of new mexico
Volcanic map of New Mexico

"Our ancestors knew how to shape these volcanic rocks into arrowheads, axe heads, corn grinding tools, and homes." – Affiliated Pueblo Committee

The geology of the Pajarito Plateau shaped the lives of the people who inhabited this landscape. The dramatic cliffs of Frijoles Canyon were created from the ash of massive volcanic eruptions.

valles caldera
Just a portion of the Valles Caldera can be seen from State Highway 4.

photo by sally king

Massive Eruptions
In New Mexico more than one million years ago, huge volcanic explosions rained ash and cinders over a 1500 square mile area. Some ash traveled as far as the Mississippi River. After the volcano emptied its magma chamber, it collapsed into itself, leaving a circular depression called a caldera. Bandelier is located on the outer slope of this caldera, known today as the Valles Caldera.

Consolidated volcanic ash forms a rock known as tuff.

photo by sally king

From Ash to Tuff
During the eruptions that formed the Valles Caldera, ash flows up to 1,000 feet thick covered the landscape from the caldera rim to the Rio Grande. As the hot ash cooled, it welded into a rock called tuff. Bandelier is located on this broad, sloping layer of tuff called the Pajarito Plateau.
home made from tuff
Homes were made from the volcanic tuff.

photo by sally king

From Tuff to Homes
Tuff is very light and soft. Over time, wind and water gradually eroded away softer areas of tuff, creating holes in the exposed canyon faces. The Ancestral Pueblo people used these to their advantage. With hand tools, they enlarged and shaped cliff openings into useful shelters called cavates (CAVE-eights). They used tuff blocks to build apartment-like homes along the cliff faces in front of the cavates.

Last updated: February 24, 2015

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Contact Info

Mailing Address:

Bandelier National Monument
15 Entrance RD

Los Alamos, NM 87544


505 672-3861 x0

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