Postcards from the Field

These are some photographs I recently took of hydromagmatic deposits along Interstate 25 near Albuquerque, about 1 mile southwest of the Isleta exit. Hydromagmatic deposits are commonly formed when ascending magma, typically of mafic composition, encounters shallow groundwater in alluvium. The several-hundred degree temperature of the magma induces the groundwater to flash into steam, and the resulting explosion hurls the relatively loose alluvial sediment, plus pieces of the magma (ash, lapilli), into the air. This mix of ejecta then falls back down relatively close to the ascending magma. Hydromagmatic deposits can be seen along the entire Rio Grande rift, from Taos south to the southern border.

Bill, I and the rest of the field team just finished up a good season at a remote volcano in West Antarctica called Mount Waesche. We left New Mexico in mid-November and, after a few days of delay in New Zealand, flew from there to McMurdo in a transport plane called a C-17. The objective of our work this season was to drill through the ice on the flanks of Mount Waesche, to sample sub-ice lava, with the goal of gaining information about when, in the past, the West Antarctic ice sheet was thinner than it is today.

The Quaternary geology of the Jornada del Muerto basin on the east side of the Fra Cristobal Range is characterized by lava flows, sand dunes, alluvial fans, and low-gradient drainages feeding into a succession of playa lake deposits. Generous permission from the Armendaris Ranch has allowed the mapping program to assess the geologic history of this area.

A group of geologists from the NMBGMR and Maya Elrick from the UNM Earth Science Department recently met up in the Rio Puerco Valley to examine Cretaceous sedimentary rocks. The outcrops will be a featured stop during next week’s New Mexico Geological Society Fall Field Conference.