Stop 3: La Poruna
La Poruna
21°53'33"S, 68°29'55"W Elevation: 3577m (11733 ft)
Just about 30 miles north of Chui Chui, lie the San Pedro and San Pablo Volcanoes on the right and the La Poruna cone directly ahead.
La Poruna is a scoria cone on the western flank of San Pedro Volcano. Several lava flows from La Poruna extend westerward for almost eight kilometers! These were mapped in O'Callaghan and Francis, 1986 as part of their work on the San Pedro/Pablo Volcanoes.
The flow is a basaltic andesite with ~59% Silica. Juvenile block from the flow was dated (via Helium surface-exposure) at 103,000 years (Worner et al, 2000).
La Poruna is one of the primary targets we have been researching as part of a project exploring lava flow morphology in satellite imagery.
More information about that project can be found here.
Up close, it is spectacular!
The next three days, we spent measuring the flow margin lobes,
exploring crease structures in the lava,
and climbing to the top of the cone for a perspective view of the flows.
On top, the team stopped for a group picture!
Additional Sources:
- O'Callaghan, L.J., and Francis, P.W., 1986. Volcanological and petrological evolution of San Pedro volcano, Provincia El Loa, North Chile. J. Geol. Soc. Lond. 143, 275-286
- Wörner, G., Hammerschmidt, K., Henjes-Kunst, F., Lezaun, J., Wilke, H. (2000). Geochronology ( ( 40 40 Ar- 39 39 Ar, K-Ar and He-exposure ages) of Cenozoic magmatic rocks from northern Chile (18°-22°S): Implications for magmatism and tectonic evolution of the Central Andes. Revista Geológica de Chile, v. 27 (02), pp. 205-240.
