Uturuncu volcano, Bolivia: Volcanic unrest due to mid-crustal magma intrusion Sparks, R. S. J. ; Folkes, C. B. ; Humphreys, M. C. S. ; Barfod, D. N. ; Clavero, J. ; Sunagua, M. C. ; McNutt, S. R. ; Pritchard, M. E. Abstract Publication: American Journal of Science Pub Date: June 2008 DOI: 10.2475/06.2008.01 Bibcode: 2008AmJS..308..727S