INFLATION AND DEFLATION IN ADEN CRATER LAVAS, DONA ANA CO., NEW MEXICO

Aden Crater lava field, 40 km southwest of Las Cruces, New Mexico, offers excellent examples of features of low viscosity basalt flows associated with an Icelandic-type shield cone. Improved images and recent field examination of the 18.2-15.7 ka lavas allow re-evaluation of the lava field’s surface features. The 1.5 km basal diameter cone is topped by a 350 m diameter crater. The flows, encompassing 75 km², extend to the south and southeast. Lava channels and small diameter lava tubes abound in the area surrounding the crater, but most of the field is comprised of pressure ridges and pressure plateaus formed by inflation of partially solidified lava crust over still mobile subcrustal lava. Narrow pressure ridges have medial fractures; whereas, pressure plateaus consist of broad areas of inflated crust with circumferential fractures. Multiple collapse pits (plateau pits) occur on the surface of inflated crust as well as a “patterned ground” texture caused by intersecting joints in the stretched basalt crust. Hornitos of spatter lava and rootless shield volcanoes—shallow craters atop low-lying domes surrounded by radial lava channels—provide avenues of escape of subcrustal lavas to the surface. Distribution of rootless pits and effusions appear to be randomly distributed across the flows.