Geology of Albuquerque

The Sandia Mountains are the predominant geographic feature visible in Albuquerque. "Sandia" is Spanish for "watermelon", and is popularly believed to be a reference to the brilliant coloration of the mountains at sunset: bright pink (melon meat) and green (melon rind). The pink is due to large exposures of granodiorite cliffs, and the green is due to large swaths of conifer forests. However, Robert Julyan notes in The Place Names of New Mexico, "the most likely explanation is the one believed by the Sandia Indians: the Spaniards, when they encountered the Pueblo in 1540, called it Sandia, because they thought the squash growing there were watermelons, and the name Sandia soon was transferred to the mountains east of the pueblo."[2] He also notes that the Sandia Pueblo Indians call the mountain Bien Mur, "big mountain."

The Sandia foothills, on the west side of the mountains, have soils derived from that same rock material with varying sizes of decomposed granite, mixed with areas of clay and caliche (a calcereous clay common in the arid southwestern USA), along with some exposed granite bedrock. Below the foothills, the area usually called the "Heights" consists of a mix of clay and caliche soils, overlain by a layer of decomposed granite, resulting from long-term outwash of that material from the adjacent mountains. This bajada is quite noticeable when driving into the Duke City from the north or south, due to its fairly uniform slope from the mountains' edge downhill to the valley. Sand hills are scattered along the I-25 corridor and directly above the Rio Grande valley, forming the lower end of the Heights.

The Rio Grande valley, due to long-term shifting of the actual river channel, contains layers and areas of soils varying between caliche, clay, loam, and even some sand. It is the only part of Albuquerque where the water table often lies close to the surface, sometimes less than 10 feet. The last significant area of Albuquerque geologically is the "West Mesa": this is the elevated land west of the Rio Grande, including the sandy terrace immediately west and above the river, and the rather sharply defined volcanic escarpment above and west of most of the developed city. The west mesa commonly has soils often referred to as "blow sand", along with occasional clay and caliche and even basalt, nearing the escarpment.