OREGON STATE UNIVERSITY

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 cone (middle foreground) and the San Pedro Volcano (right) 

(Click for a larger view)  

 

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. 

Geologic Map of LaPoruna

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 from an aerial photograph

 

 

 

 

 

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!   

 

La Poruna Cone

 


 

The next three days, we spent measuring the flow margin lobes,

Measuring Lobes at La Poruna 

 

exploring crease structures in the lava,  

 

Axel explores a crease structure   

 

and climbing to the top of the cone for a perspective view of the flows.  

 

The view from the summit of La Poruna   

 

On top, the team stopped for a group picture! 

 

 The team poses for a group shot on top of La Poruna

 

 


 

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.