Structure and Evolution
A classically symmetrical conical volcano, Licancabur (Figure 23.1; 23.2) has a circular basal plan with a diameter of ~10 km, and appears to have been largely constructed in post-glacial times (compare the pre-Holocene Volcan Juriques (J) to the east). There is abundant evidence of recent activity in the form of youthful lava flows; a well preserved summit crater, and an absence of glacial geomorphic features. Marinovic & Lahsen (1984) reported that the cone is made up predominantly of lavas interbedded with minor pyroclastic deposits. Young lavas (i.e. L) are particularly well developed on the western flanks of the volcano and extend for up to 6 km down the regional slope of about 3° on which Licancabur is built (Figure 23.2). Levées and flow ridge morphologies are well preserved on the thick (50-100m), blocky lava flows. Within the 400 m diameter summit crater (SC) is a fresh water lake, about 90 m x 70 m. This is one of the highest lakes in the world and hosts a planktonic fauna of considerable interest to biologists. A high altitude diving expedition in 1984 found the lake to be <4m deep with a temperature of 6 °C at the bottom (Leach, 1986). Ruins of archaeological interest are present on the rim of the crater (Rudolph, 1955).
Little is known about the earliest activity, but as with many of the other centres in this region, the oldest lava flows extend considerably further than the youngest. Flows on the west extend for ~12 km from the present centre and their distal portions divide into several thin flows extending 1-3 km from the main lava body (~9 km from the volcano). Flank lava flows are the most recent activity from this Licancabur. There are no records of historic eruptions.
No current activity is known. However, the presence of the crater lake at an altitude close to 6000m with a bottom temperature of 6⩝C indicates that a mild thermal source exists to maintain the lake water above freezing and support the fauna. The chemistry of the lake supports the theory of geothermal fluid input.
Marinovic and Lahsen (1984) report that the lavas from Licancabur are porphyritic pyroxene andesites and are typical of those from Escalante and Sairecabur to the north. Typically plagioclase, Ca-augite, brinzite, and opaques with minor hornblende, biotite, and quartz are found constituting between 20% and 40% of the lava. An analysis from one of the older lavas has 60.21% SiO2 (S. de Silva, unpublished data, 1990). Figueroa and Deruelle (1996) found geochemical variations between the oldest and youngest lava flows.
Figueroa, O., and Deruelle, B., 1996. Licancabur, an andesitic volcano of the south-central Andes. Third ISAG, St Malo (France), 17-19/9/1996, p. 563-566.
Hock, A.N., Cabrol, N.A., Grin, E.A., Fike, D.A., & Paige, D.A., 2002. Licancabur Expedition Team 2003, EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003.
Leach, J.W.P., 1986. Andean high altitude expedition. Underwater Technology, v.12, No. 1, p 27-31
Marinovic-N, and Lahsen-A. (1984) Hoja Calama. Carta Geologica de Chile, 58. SNGM, Santiago.
Rudolph, W.E., 1955. Licancabur: Mountain of the Atacameños. Geographical Review, v. 45, p.151-171.