Aden Crater is a small

shield volcano A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava ...

located in Doña Ana County, about southwest of

Las Cruces, New Mexico Las Cruces (; ; lit. 'the crosses') is the List of municipalities in New Mexico, second-most populous city in the U.S. state of New Mexico and the county seat, seat of Doña Ana County, New Mexico, Doña Ana County. As of the 2020 United States ce ...

. 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. 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 preserve ...

ized

ground sloth Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. They varied widely in size with the largest, belonging to genera '' Lestodon'', ''Eremotherium'' and ''Megatherium'', being around the size of elephants. ...

, now at the Peabody Museum, was found in a

fumarole A fumarole (or fumerole) is a vent in the surface of the Earth or another 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% ...

. 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 volcano, volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone (geometry), cone with a central crater. Volcanic cones are of different types, depen ...

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 Volcanic cone#Spatter cone, spatter cones but are rootless, meaning they were o ...

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 Chihuah ...

, where the

Earth's crust Earth's crust is its thick outer shell of rock, referring to less than one percent of the planet's radius and volume. It is the top component of the lithosphere, a solidified division of Earth's layers that includes the crust and the upper ...

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 subsidence ...

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 mineral, silicate rock between the Earth's crust, crust and the Earth's outer core, outer core. It has a mass of and makes up 67% of the mass of Earth. It has a thickness of making up about 46% of Earth's ...

. 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.

Description

Geologic setting

References

Further Reading