Evolution of the late Cenozoic Jornado volcano, south-central New Mexico
Jerry M. Hoffer and L. LeRoy Corbitt
The Jornada volcano is a late Cenozoic (<0.76 ± 0.1 Ma) basaltic-lava shield cone within the 435 km2 Jornada basalt field in southern Socorro and northern Sierra Counties. The field consists of three major alkali olivine basalt flows emplaced from a series of north-striking fissures. The lava cone sits on top of the lava flows and covers an area of approximately 6 km2. The principal volcanic features associated with the Jornada volcano include two centrally extruded lava flows, a well-developed lava tube system, and a central crater containing several cinder-spatter cones and collapse features. The most unusual feature is a moat which encircles the central crater on its west, south and east sides. The moat ranges in width from 20 to 200 m and in depth from I to 13 m. A number of "islands" composed of lava flow and spatter layers occur on the floor of the moat; the height of these blocks is nearly equal to the depth of the moat. The major events involved in the formation of the lava cone include alternating episodes of lava fountaining, quiet extrusion of fluid lava, and collapse (moat formation).
- Hoffer, Jerry M.; Corbitt, L. LeRoy, 1991, Evolution of the late Cenozoic Jornado volcano, south-central New Mexico, in: Geology of the Sierra Blanca, Sacramento and Capitan Ranges, New Mexico, Barker, James M.; Kues, Barry S.; Austin, George S.; Lucas, Spencer, G., New Mexico Geological Society, Guidebook, 42nd Field Conference, pp. 159-163.