Tolhuaca

Tolhuaca (or Tolguaca) is a late-Pleistocene to Holocene stratovolcano located immediately NW of Lonquimay volcano. A NW-SE zone of aligned summit craters is youngest to the NW. Another group of vents cutting the south and east flanks is oriented SW-NE, parallel to the zone of flank vents on Lonquimay, and is of post-glacial age (Moreno and Gardeweg 1989).

Reports of eruptions in 1876 and on 7 January 1933 are not confirmed; the latter date probably refers to an eruption of Lonquimay or Llaima (Petit-Breuilh 1994, pers. comm. ).

Polanco et al. (2000) stated that explosive activity consisted of three VEI 3-4 eruptions between 8050 and 6590 BP. The Pemehue volcanic trend on the NW flank was noted by Naranjo (pers.

comm. 2010) in Melosh et al. (2012) as having post-glacial lava flows dated at less than 6,000 years old.

Only fumarolic activity has occurred from this basaltic-andesitic volcano during historical time. Fumaroles and hot springs are common across the NW flank where there is an active geothermal reservoir (Melosh et al. , 2012).