Three cinder cones appear on Albuquerque’s west mesa, few miles west of the Rio Grande River.
Locals refer to them as the Three Sisters or the Albuquerque Volcanoes. Geologically, they are the visible remains of a fissure type volcano that was several miles long and spewed slow moving lava. This fissure is a small part of the volcanic activity generated by the Rio Grande Rift Valley. Link
The lava filled low lying arroyos and, upon cooling, formed a distinctive escarpment around one hundred feet high.
Much of the escarpment eroded into large rough boulders and cliffs.
However, some of the boulders have a smooth surface. Indigenous artists used stone harder than the basalt to chip designs onto the plane surface.
Some of the images are representational and depict humanoid figures
Some of the images appear to be more abstract.
Spanish era artists, inspired by their indigenous predecessors, also pecked away at the rocks as the cross in the picture illustrates.
Petroglyph National Monument protects many of these works of art. Link
Travels with Owen 