Aden Crater is a small shield volcano located in

Doña Ana County Don (; ; pt, Dom, links=no ; all from Latin ', roughly 'Lord'), abbreviated as D., is an honorific prefix primarily used in Spain and Hispanic America, and with different connotations also in Italy, Portugal and its former colonies, and Croatia ...

, about southwest of

Las Cruces, New Mexico Las Cruces (; "the crosses") is the second-largest city in the U.S. state of New Mexico and the seat of Doña Ana County. As of the 2020 census the population was 111,385. Las Cruces is the largest city in both Doña Ana County and southern Ne ...

. It is located in the northwest part of the Aden-Afton basalt field, which is part of the central area of the

Potrillo volcanic field The Potrillo volcanic field is a Monogenetic volcanic field, monogenetic volcanic field located on the Rio Grande Rift in southern New Mexico, United States and northern Chihuahua (state), Chihuahua, Mexico. The volcanic field lies southwest of ...

. A

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

ized ground sloth, now at the Peabody Museum, was found in a

fumarole A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...

roughly 100' deep located on the SE portion of the crater rim. Several ground sloth coprolites were also recovered and were stored in the Geology department at UTEP. No volcanic activity at Aden Crater is known from historic times. The most recent known activity has been dated to roughly 16,000 years ago. The flows associated with the crater can be divided into two groups. The earlier lavas were more fluid and formed most of the flows to the east and south of the crater. These flows are characterized by inflation plateaus, formed when a solid crust begins to develop around a flow and the lava inflates the more ductile upper surface of the flow. The second group of flows were less fluid and accumulated closer to the vent to form the shield of the crater.

Description

Aden Crater is an Icelandic-type shield volcano, formed by repeated eruptions of very fluid

olivine basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

. This has built a very low hill in diameter with slopes of just 3 to 5 degrees. The hill is topped by a crater about in diameter whose rim is composed of lava spatter that dips steeply into the crater (30 to 45 degrees). The crater itself contains a former lava lake, with a

spatter cone Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and s ...

and collapse pit in the southeastern part of the crater. The surrounding area has such features as explosion craters, collapse pits, spatter cones, and

hornito Hornitos are conical, or pipe-like, structures built up by lava spattering or being ejected through an opening in the crust of a lava flow. Hornitos are similar to spatter cones but are rootless, meaning they were once a source of lava but th ...

s. Many of these are found on a low ridge extending to the southeast. A cluster of spatter cones is found southwest of the crater. A striking feature of the area around the crater is the presence of ''herraduras''. These are horseshoe-shaped lava ridges with the open end pointing downslope. These are thought to have formed where lava was extruded through a fracture in the crust of an underlying flow, perhaps where gas accumulated and promoted fracturing.

Geologic setting

The Potrillo volcanic field is located within the

Rio Grande rift The Rio Grande rift is a north-trending continental rift zone. It separates the Colorado Plateau in the west from the interior of the North American craton on the east. The rift extends from central Colorado in the north to the state of Chihuahu ...

, where the Earth's crust is being stretched and thinned. The rift is characterized by deep

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subside ...

s, recent faulting and volcanic activity, and unusually high heat flow upwards from the

Earth's mantle Earth's mantle is a layer of silicate rock between the crust and the outer core. It has a mass of 4.01 × 1024 kg and thus makes up 67% of the mass of Earth. It has a thickness of making up about 84% of Earth's volume. It is predominantly so ...

. Aden Crater is located atop the Aden rift, which runs northwest to southeast through the crater and is traced by collapse pits to the southeast. It is near the Robledo fault, a north–south fault of the Rio Grande rift. Both the rift and the fault are thought to have provided paths to the surface for erupting magma.

References

Volcanoes of New Mexico Landforms of Doña Ana County, New Mexico Mountains of New Mexico Organ Mountains–Desert Peaks National Monument Mountains of Doña Ana County, New Mexico {{NewMexico-geo-stub