Geologic Formations

New Mexico Geologic Map

New Mexico Tech

The Salinas Pueblo Missions National Monument in central New Mexico is a testament to the geology that underlies the region. The Early Permian was a time when the continents were not separate, but a single supercontinent called Pangea. New Mexico was equatorial with the Hueco seaway to the south and floodplains covering the areas surrounding Mountainair. As the environment changed, so did the rocks.

The geology in central New Mexico is marked by a distinct carbonate bed, which is the result of rising sea levels. As the Hueco Seaway to the south encroaches on central New Mexico, the area becomes a semi-arid coastline. changing sea levels create carbonate layers and near-shore sands, while expansive tidal flats result in large deposits of gypsum, a mineral that precipitates from evaporating water bodies (also known as an evaporite).

Between 20 and 15 million years ago, the Rio Grande rift began to form to the west, allowing molten rock to make its way towards the surface in the form of dikes. These dikes can be found in abundance beneath Gran Quivira. After these molten intrusions, the geology in the area is at a standstill until nearly 45 thousand years ago when lakes covered the Estancia basin, forming Lake Estancia. Each of the three park units were close to its shores until it finally dried up.

The most recent geology of this area is what most would look at and call dirt, much of it deposited from erosion of the Manzano Mountains and the underlying Permian bedrock. The park units of Abó and Quarai looked very different 280 million years ago, with seasonal monsoons bringing iron-rich sediment from higher elevations to the rivers that meandered through the plains. The Abo Formation gradually became the Arroyo de Alamillo Formation, recording a much drier environment with wind-swept sand dunes and the occasional riverbed.

Paleontology of the Abo Formation in New Mexico has been studied for several decades, with footprints and trackways being the most common animal fossils found within park boundaries. The Yeso Group, previously thought to be not fossiliferous, has seen trackways, plants, marine, and even skeletal fossils in these formations.

A rich history of volcanic activity characterizes New Mexico's geological landscape, showcasing numerous extinct and potentially active volcanic formations. Notable extinct volcanoes include Mount Taylor, the Jemez Mountains, the Albuquerque volcanoes (also known as the Three Sisters), and Capulin Volcano. Evidence of recent volcanic activity is found in lava flows near Grants (El Malpais) and Carrizozo, dated to approximately 3,000 and 5,000 years ago, respectively.

Geologists currently regard the Valles Caldera as active, and the Rio Grande Rift is identified as a zone of active crustal thinning, although no volcanoes are presently erupting in the state. The Valles Caldera is a significant supervolcano that erupted about one million years ago, forming one of the world's largest youthful calderas, It is part of the Jemez Mountains volcanic region.

Capulin Volcano's last eruption took place between 56,000 and 62,000 years ago. The El Malpais and Carrizozo Lava Flows represent New Mexico's youngest volcanic flows. The Albuquerque Volcanoes are a notable example of extinct fissure eruptions along the Rio Grande Rift.

Ship Rock, located in the Navajo volcanic region, is a volcanic neck, representing eroded volcanic remnants from around 30 million years ago. The Petroglyph National Monument contains several volcanic phenomena, including the Albuquerque Volcanoes, scoria cones, and lava flows.

Several national monuments and preserves have been established to protect these volcanic sites, including Valles Caldera National Preserve, Capulin Volcano National Monument, Petroglyph National Monument, and El Malpais National Monument. The Carrizozo Lava Flow is in south-central New Mexico.