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| Photo from the New Mexico Museum of Natural History & Science |
One of my memories from living in Albuquerque was staring across the Rio Grande valley at the three volcanoes on the West Mesa.
I didn't know much about the mysterious three black hills that stood out against the pale desert sand. We all heard stories that they were volcanoes, yet we didn't learn anything about them in school. No field trips out to see them.
Tonight I was doing some browsing and happened upon the New Mexico Museum of Natural History & Science website where they have a really detailed article about the volcanoes, plus all the other ones around the state.
I was sad to learn that there are trails where you can hike around them, something I would have loved to do back in the 80s when I lived there.
Now I will just have to take a trip out there to explore them.
History:
The Albuquerque Volcanoes exhibit many unique volcanic features and you can see them on a short hike if you know where to look. For example, at the largest cone, "Vulcan volcano", the cone consists mostly of scoria and ash, but has a carapice of spatter and lava coating the exterior. Gradual weathering of the loose cinders in these places has created cavernous holes. These look like lava tubes but actually were formed by a different process. Then there are other places on the larger cones where lava flowed in small gutters perfectly preserved with the last flows on the gutter floors.Two humps on the south side of Vulcan are actually small volcanoes. You can stand on their tops and actually see the craters surrounded by outward-dipping spatter and lava flows.
The Albuquerque Volcanoes are the source of lavas that make up the escarpment of the Petroglyphs National Monument. In places the cliffs are over a hundred feet high. But the lava flows are only six to ten feet thick in most places and occur as a cap rock resting on softer underlying rift basin fill consisting of sands and gravels. The rest of the cliff or petroglyph slope is just armored with blocks of basalt that have tumbled from the relatively thin lava flow cap rock. Judging from these high cliffs at the edge of the lava field, one might also suppose that the volcanoes are old. But the Volcano Cliffs, as they are known locally, formed only because the Rio Grande flow gradually cut down its channel and the lateral erosion of the landscape has encroached on the lava flows from the volcanoes under cutting them and leaving them perched on escarpments.
Here is the important thing about the Albuquerque Volcanoes: Few large cities in the United States have young volcanoes near them. The Albuquerque Volcanoes are geologically young (dates range between about 190,000 and 220,000 years old) so many details of small eruptions are well preserved. What is ironic is the fact that most residents see them as such small hills on the western horizon that they could not possibly be of any interest. But it turns out that they preserve some really unusual characteristics not seen in other more spectacular volcanic settings.
They are also an excellent example of the results of a fissure eruption in which a curtain of fire erupts from a long, linear crack. Fissure eruptions like the Albuquerque Volcanoes are common in many parts of the world, particularly oceanic island volcanoes, but are not as well-expressed throughout much of the Southwest.
The Albuquerque Volcanoes we see today are the result of a fissure eruption associated with the Rio Grand rift. Fissure eruptions form because molten rock, or magma, tends to rise along vertical cracks. When the cracks reach the surface, they cause long surface fissures. Lava and ash then erupt from the fissure. As magma quickly cools and solidifies along most of the crack, only a few points continue to erupt. Small cones of ash, spatter, and lava are built as these points of eruption continue.
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