The whole national monument is an area formed when the Albuquerque Volcanoes (photo at bottom of entry) erupted about 150,000 years ago. The cinder cones are dormant now, but do show up as peaks along the western side of the monument. Basalt rock formed a cap rock from the lava flows and over the years, has been undercut by the softer sandy soils underneath, causing basalt boulders to tumble down to create the escarpment edge. The boulders have been exposed to sun, wind, rain, heat, and even microorganisms that created a thin layer of something called "desert varnish" (see above right) on the boulders that could be chipped off by the Ancestral Puebloan people with a rock or chisel stone to form a lighter picture underneath.
Along the Boca Negra Canyon trails, Ancestral Puebloans carved many different petroglyphs that date from between the 1300's to 1600's in what is called the Rio Grande style. We saw kokopellis, dancers, masks, animals, snakes, birds, human hands, stars, and spirals. Can you find these petroglyphs in the rocks below? We especially like the two dancers, one woman and one man, with the man dancing on what looks to be a chicken. We did see so many more great pictures; it was exciting to walk the trails and see each new image.
Something else that I thought was neat was basalt boulders that had these stripes in them. I read the plaque next to it that said that they formed when the rock cracked and later filled back in with new lava. It made me think of columnar jointing that occurs in basalts and wondered if it was related.
The views from the top of the mesa were really great. We were a mile above sea level overlooking the whole town of Albuquerque and Sandia Peak. The skies were a bit hazy, though, so things weren't too clear. At 10 am it was already 80 degrees. After our hike along the trails, we decided to do a little bit of geocaching and found 3 out of the 4 caches just north of the national monument, near the volcanoes. These are the three largest ones (right to left): Vulcan Volcano, Black Volcano, and JA Volcano. I hope to take another trip to explore them soon.
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