Жаңа Мексикадағы Килбурн кратері

Maar in New Mexico, United States

[[File:Kilbourne Hole basalt. jpg|thumb|upright|Basalt cliffs of Kilbourne Hole, looking northwest from near the southwest corner. The cliffs come from the earlier Cenozoic Afton basalt flow; the magma that caused the maar explosion was also basalt. In 1975, Kilbourne Hole was designated as a National Natural Landmark by the National Park Service. It is now part of Organ Mountains–Desert Peaks National Monument.

Kilbourne Hole and Hunt's Hole are found in the central part of the Potrillo volcanic field, which also contains the Afton Aden basalt flows. The area is part of the Rio Grande rift, where the Earth's crust is being stretched and thinned. The rift is characterized by deep sedimentary basins, recent faulting and volcanic activity, and unusually high heat flow upwards from the Earth's mantle. Kilbourne Hole and Hunt's Hole are located on the same north trending fault of the Fitzgerald Robledo fault system. A maar forms when rising magma encounters sediment beds saturated with groundwater. The magma heats the groundwater to the point where the vapor pressure overcomes the weight of the overlying beds (the overburden pressure) and the beds are catastrophically blown out. Country rock is fragmented and expelled into the atmosphere together with fragments of the magma, creating a deep crater, the bottom of which sits below the pre eruptive ground surface. Kilbourne Hole erupted through alluvium (unconsolidated water deposited sediments) and through a thin basalt flow. Like most maars, it has a shallow rim, composed of erupted material that was deposited as thin pyroclastic surge deposits. The hole is over a mile wide, and over 300 feet (91 m) deep, with crumbling cliffs all around except at the southwest corner. The rim cliffs, measuring about 40 feet (12 m) in height, are composed of basalt and exhibit clear columnar jointing (a feature common to many basalt cliffs, including those of Devils Postpile National Monument near Yosemite National Park and Moses Coulee in the Channeled Scablands of Washington), with characteristic reddish purple, polygonal (mostly hexagonal) columns. The base of the cliffs is obscured by scree composed of blocks of basalt that have been dislodged from the columns above by the work of erosion and mechanical weathering. The basalt flow that comprises these columns pinches out (thins) and eventually disappears as it approaches the southwestern rim of the maar.

Kilbourne Hole is located within Organ Mountains–Desert Peaks National Monument and administered by the Bureau of Land Management. It is accessed via Doña Ana County Road A 011, driving 8 mile (13 km) west from the railroad. The hole is "on the right, past the big tan dirt bank." Much of the land inside the hole is private property. Hunt's Hole is about 2 mile (3 km) south on A 013.